Radical Islamist terrorism in its many forms remains the most immediate global threat to the safety and security of U.S. citizens at home and abroad, and Iran-supported terrorist groups and proxy militias pose some of the greatest potential threats. The Lebanon-based Hezbollah (Party of God) has a long history of executing terrorist attacks against American targets in the Middle East at Iran’s direction, and it could be activated to launch attacks inside the United States in the event of a conflict with Iran. Such state-sponsored terrorist attacks pose the greatest potential Iranian threats to the U.S. homeland, at least until Iran develops a long-range ballistic missile capable of targeting the United States or acquires the capability to launch devastating cyberattacks against critical U.S. infrastructure.
Threats to the Homeland
Hezbollah Terrorism. Hezbollah, the radical Lebanon-based Shia revolutionary movement, poses a clear terrorist threat to international security. Hezbollah terrorists have murdered Americans, Israelis, Lebanese, Europeans, and citizens of many other nations. Originally founded with support from Iran in 1982, this Lebanese group has evolved into a global terrorist network that is strongly backed by regimes in Iran and Syria. Its political wing has dominated Lebanese politics and is funded by Iran and a dark web of charitable organizations, criminal activities, and front companies.
Hezbollah regards terrorism not only as a useful tool for advancing its revolutionary agenda, but also as a religious duty as part of a “global jihad.” It helped to introduce and popularize the tactic of suicide bombings in Lebanon in the 1980s, developed a strong guerrilla force and a political apparatus in the 1990s, provoked a war with Israel in 2006, intervened in the Syrian civil war after 2011 at Iran’s direction, and has become a major destabilizing influence in the ongoing Arab–Israeli conflict.
Before September 11, 2001, Hezbollah had murdered more Americans than any other terrorist group. Despite al-Qaeda’s increased visibility since then, Hezbollah remains a bigger, better equipped, better organized, and potentially more dangerous terrorist organization, partly because it enjoys the support of the world’s two chief state sponsors of terrorism: Iran and Syria. Hezbollah’s demonstrated capabilities led former Deputy Secretary of State Richard Armitage to characterize it colorfully as “the A-Team of Terrorists.”1
Hezbollah has expanded its operations from Lebanon to regional targets in the Middle East and far beyond the region. Today, it is a global terrorist threat that draws financial and logistical support from its Iranian patrons as well as from the Lebanese Shiite diaspora in the Middle East, Europe, Africa, Southeast Asia, North America, and South America. Hezbollah fundraising and equipment procurement cells have been detected and broken up in the United States and Canada, and Europe is believed to contain many more of these cells.
Hezbollah has been involved in numerous terrorist attacks against Americans, including:
- The April 18, 1983, suicide truck bombing of the U.S. embassy in Beirut, which killed 63 people including 17 Americans;
- The October 23, 1983, suicide truck bombing of the Marine barracks at Beirut Airport, which killed 241 Marines and other personnel deployed as part of the multinational peacekeeping force in Lebanon;
- The September 20, 1984, suicide truck bombing of the U.S. embassy annex in Lebanon, which killed 23 people including two Americans; and
- The June 25, 1996, Khobar Towers bombing, which killed 19 American servicemen stationed in Saudi Arabia.
- Hezbollah operatives were later found to have been responsible for the 1984 murder of American University of Beirut President Malcolm Kerr and the June 14, 1985, murder of U.S. Navy diver Robert Stethem, who was a passenger on TWA Flight 847, which was hijacked and diverted to Beirut International Airport.
- In March 1984, Hezbollah kidnapped William Buckley, the CIA station chief in Beirut, who died in captivity in 1985 after being tortured for more than a year.2
- Hezbollah was involved in the kidnapping of several dozen Westerners, including 14 Americans, who were held as hostages in Lebanon in the 1980s. The American hostages eventually became pawns that Iran used as leverage in the secret negotiations that led to the Iran–Contra affair in the mid-1980s.
- Hezbollah kidnapped Colonel William Higgins, a Marine officer serving with the United Nations Truce Supervision Organization in Lebanon, in February 1988 and killed him in 1989.
Hezbollah has launched numerous attacks outside of the Middle East. It perpetrated the two deadliest terrorist attacks in the history of South America: the March 1992 bombing of the Israeli embassy in Buenos Aires, Argentina, that killed 29 people and the July 1994 bombing of a Jewish community center in Buenos Aires that killed 96 people. The trial of those who were implicated in the 1994 bombing revealed an extensive Hezbollah presence in Argentina and other countries in South America.
Hezbollah has escalated its terrorist attacks against Israeli targets in recent years as part of Iran’s shadow war against Israel. In 2012, Hezbollah killed five Israeli tourists and a Bulgarian bus driver in a suicide bombing near Burgas, Bulgaria. Hezbollah terrorist plots against Israelis were foiled in Thailand and Cyprus during that same year.
Hezbollah deployed personnel to Iraq after the 2003 U.S. intervention to train and assist pro-Iranian Iraqi Shia militias that were battling the U.S.-led coalition. In addition, Hezbollah has deployed personnel in Yemen to train and assist the Iran-backed Houthi rebels. In 2013, Hezbollah admitted that it had deployed several thousand militia members to fight in Syria on behalf of the Assad regime. By 2015, Hezbollah forces had become crucial to the survival of the Assad regime after the Syrian army was hamstrung by casualties, defections, and low morale.
Although Hezbollah operates mostly in the Middle East, it has a global reach and has established a presence inside the United States. Cells in the United States generally are focused on fundraising, including criminal activities such as those perpetrated by more than 70 used-car dealerships identified as part of a scheme to launder hundreds of millions of dollars of cocaine-generated revenue that flowed back to Hezbollah.3
Covert Hezbollah cells could morph into other forms and launch terrorist operations inside the United States. Given Hezbollah’s close ties to Iran and past record of executing terrorist attacks on Tehran’s behalf, there is a real danger that Hezbollah terrorist cells could be activated inside the United States in the event of a conflict between Iran and the U.S. or between Iran and Israel.
On June 1, 2017, two naturalized U.S. citizens were arrested and charged with providing material support to Hezbollah and conducting preoperational surveillance of military and law enforcement sites in New York City and at Kennedy Airport, the Panama Canal, and the American and Israeli embassies in Panama.4 Nicholas Rasmussen, then Director of the National Counterterrorism Center, noted that the June arrests were a “stark reminder” of Hezbollah’s global reach and warned that Hezbollah “is determined to give itself a potential homeland option as a critical component of its terrorism playbook,” which “is something that those of us in the counterterrorism community take very, very seriously.”5
On July 9, 2019, a New Jersey man who served as a U.S.-based operative for Hezbollah’s terrorism-planning wing for years, was arrested and charged with providing material support to the terrorist group. Alexei Saab, a 42-year-old Lebanese immigrant and naturalized U.S. citizen, scouted such New York City landmarks as the Statue of Liberty and the Empire State Building for possible attacks. When he was indicted in September 2019, he was “at least the third American [to have been] charged since 2017 with being an agent for Hezbollah.”6
In January 2020, after a series of attacks on U.S. military personnel and the U.S. embassy in Iraq provoked a U.S. unmanned aerial vehicle (UAV) strike that killed Iranian General Qassem Soleimani, leader of the Quds Force of Iran’s Islamic Revolutionary Guard Corps (IRGC), U.S. intelligence officials warned about the potential Hezbollah threat to the U.S. homeland. The Department of Homeland Security warned in a January 4, 2020, bulletin that “Iran and its partners, such as Hizballah, have demonstrated the intent and capability to conduct operations in the United States.”7 Four days later, the U.S. intelligence community warned that if Iran decided to carry out a retaliatory attack in the United States, it “could act directly or enlist the cooperation of proxies and partners, such as Lebanese Hezbollah.”8 Then, on January 12, Hezbollah leader Hassan Nasrallah publicly threatened U.S. forces in the Middle East: “The U.S. administration and the assassins will pay a heavy price, and they will discover their miscalculation.”9
Hezbollah also has a long history of cooperation with criminal networks. On May 27, 2020, U.S. prosecutors announced the indictment of a former Venezuelan politician who sought to recruit terrorists from Hezbollah and Hamas to orchestrate attacks against U.S. interests. Adel El Zabayar, a Venezuelan citizen of Syrian descent who is a close associate of Venezuelan President Nicolás Maduro, traveled to the Middle East in 2014 to obtain weapons and recruit members of Hezbollah and Hamas to train at hidden camps in Venezuela. The goal of this “unholy alliance,” according to the U.S. Attorney’s Office for the Southern District of New York, was to “create a large terrorist cell capable of attacking United States interests on behalf of the Cartel de Los Soles,” a criminal organization that “conspired to export literally tons of cocaine into the U.S.”10
Iran’s Ballistic Missile Threat. Iran has an extensive missile development program that has received key assistance from North Korea, as well as (until the imposition of sanctions by the U.N. Security Council) more limited support from Russia and China. Although the U.S. intelligence community assesses that Iran does not have an ICBM capability (an intercontinental ballistic missile with a range of 5,500 kilometers or about 2,900 miles), Tehran has worked diligently to develop one under the guise of its space program. Iran is not likely to develop missiles capable of reaching the United States until 2025 at the earliest.11 However, it has launched several satellites with space launch vehicles that use similar technology, which could also be adapted to develop an ICBM capability.12
On April 22, 2020, Iran launched a military satellite with a new launch vehicle that included such new features as a light carbon fiber casing and a moving nozzle for flight control that is also used in long-range ballistic missiles—clear evidence that Iran continues to improve its capabilities.13 Tehran’s missile arsenal primarily threatens U.S. bases and allies in the Middle East, but Iran eventually could expand the range of its missiles to include the continental United States. Iran is the only country that is known to have developed missiles with a range of 2,000 kilometers without first having nuclear weapons.14
Threat of Regional War
The Middle East region is one of the most complex and volatile threat environments faced by the United States and its allies. Iran, Hezbollah, and Iran-supported proxy groups pose actual or potential threats both to America’s interests and to those of its allies.
Iranian Threats in the Middle East. Iran is led by an anti-Western revolutionary regime that seeks to tilt the regional balance of power in its favor by driving out the U.S. military presence, undermining and overthrowing opposing governments, and establishing its hegemony over the oil-rich Persian Gulf region. It also seeks to radicalize Shiite communities and advance their interests against Sunni rivals. Iran has a long record of sponsoring terrorist attacks against American targets and U.S. allies in the region.
Iran’s conventional military forces, although relatively weak by Western standards, are large compared to those of Iran’s smaller neighbors. Iran’s armed forces remain dependent on major weapons systems and equipment that were imported from the U.S. before the country’s 1979 revolution, and Western sanctions have limited the regime’s ability to maintain or replace these aging weapons systems, many of which were depleted in the 1980–1988 Iran–Iraq war. Iran also has not been able to import large numbers of modern armor, combat aircraft, longer-range surface-to-surface missiles, or major naval warships.
Tehran, however, has managed to import modern Russian and Chinese air-to-air, air-to-ground, air defense, anti-armor, and anti-ship missiles to upgrade its conventional military and asymmetric forces.15 It also has developed its capacity to reverse engineer and build its own versions of ballistic missiles, rockets, UAVs, minisubmarines, and other weapon systems. To compensate for its limited capability to project conventional military power, Tehran has focused on building up its asymmetric warfare capabilities, proxy forces, and ballistic missile and cruise missile capabilities. For example, partly because of the limited capabilities of its air force, Iran developed UAVs during the Iran–Iraq war, including at least one armed model that carried up to six RPG-7 rounds in what was perhaps the world’s first use of UAVs in combat.16
The July 2015 Iran nuclear agreement—formally known as the Joint Comprehensive Plan of Action (JCPOA)—lifted nuclear-related sanctions on Iran in January 2016, gave Tehran access to about $100 billion in restricted assets, and allowed Iran to expand its oil and gas exports, the chief source of its state revenues. Relief from the burden of sanctions helped Iran’s economy and enabled Iran to enhance its strategic position, military capabilities, and support for surrogate networks and terrorist groups.
In May 2016, Tehran announced that it was increasing its military budget for 2016–2017 to $19 billion—90 percent more than the previous year’s budget.17 Estimating total defense spending is difficult both because of Tehran’s opaque budget process and because spending on some categories, including Iran’s ballistic missile program and military intervention in Syria, is hidden. Nevertheless, the International Institute for Strategic Studies (IISS) has estimated that after the Trump Administration withdrew from the nuclear agreement and reimposed sanctions, Iran’s defense spending fell from $21.9 billion in 2018 to $17.4 billion in 2019.18 In 2020, according to the IISS, defense spending declined again to an estimated $14.1 billion.19
The 2015 nuclear agreement also enabled Tehran to emerge from diplomatic isolation and strengthen strategic ties with Russia.
- Russian President Vladimir Putin traveled to Iran in November 2015 to meet with Supreme Leader Ayatollah Ali Khamenei and other officials. Both regimes called for enhanced military cooperation, particularly in Syria where both had deployed military forces in support of President Bashir al-Assad’s brutal regime.
- During Iranian President Hassan Rouhani’s visit to Russia in March 2017, Putin proclaimed his intention to raise bilateral relations to the level of a “strategic partnership.”20
- On June 9, 2018, during the Shanghai Cooperation Organization (SCO) summit, Putin noted that Iran and Russia were “working well together to settle the Syrian crisis” and promised Rouhani that he would support Iran’s entry into the SCO.21
- On September 16, 2019, in Ankara, Turkey, ahead of a trilateral meeting with Turkish President Recep Tayyip Erdogan to discuss the situation in Syria, the two presidents met again, and Putin praised Iran’s support for the Assad regime.
This growing strategic relationship has strengthened Iran’s military capabilities. In April 2016, Tehran announced that Russia had begun deliveries of up to five S-300 Favorit long-range surface-to-air missile systems, which can track up to 100 aircraft and engage six of them simultaneously at a range of 200 kilometers.22 The missile system, which was considered a defensive weapon not included in the U.N. arms embargo on Iran, was deployed and became operational in 2017, giving Iran a “generational improvement in capabilities over its other legacy air defense systems” according to Defense Intelligence Agency Director Lieutenant General Robert Ashley.23
In 2016, Iranian Defense Minister Hossein Dehghan traveled to Moscow “to negotiate a series of important weapons deals with Russia” that included the purchase of advanced Sukhoi Su-30 Flanker fighter jets. These warplanes would significantly improve Iran’s air defense and long-range strike capabilities, although under the terms of the 2015 Iran nuclear agreement, they could not be delivered until after the U.N. arms embargo expired in October 2020. It was also reported that Tehran was “close to finalizing a deal for purchase and licensed production of Russia’s modern T-90S main battle tank.”24
In 2019, the Defense Intelligence Agency assessed that Iran was interested in buying Russian Su-30 fighters, Yak-130 trainers, T-90 tanks, S-400 air defense systems, and Bastian coastal defense systems.25 So far, Russia and Iran have not announced any arms deals, but Moscow may be waiting to see whether the Iran nuclear agreement can be renegotiated, which would enable it to receive payments from Iran after U.S. financial sanctions were lifted. In January 2022, President Ebrahim Raisi met with President Putin in Moscow. The two agreed to accelerate the construction of Russian nuclear reactors in Bushehr, Iran, but Putin appeared to be lukewarm about the draft of a strategic cooperation agreement that Raisi brought with him.26 Clearly, Iran needs Russia more than Russia needs Iran.
If Iran should succeed in reviving the lapsed nuclear agreement, Russian–Iranian security cooperation could expand significantly. After the 2015 nuclear agreement, Iran and Russia escalated their strategic cooperation in propping up Syria’s embattled Assad regime. Iran’s growing military intervention in Syria was partly eclipsed by Russia’s military intervention and launching of an air campaign against Assad’s enemies in September 2015, but Iran’s Islamic Revolutionary Guard Corps and surrogate militia groups have played the leading role in spearheading the ground offensives that have retaken territory from Syrian rebel groups and tilted the military balance in favor of Assad’s regime.
- From 2013–2015, “Iran expanded its intervention in Syria to as many as 2,000 Iranian military personnel…including IRGCQF, IRGC ground force, and even some Artesh (Iran national military) personnel.”27
- From 2013–2017, “[t]he IRGC-QF recruited other Shia fighters to operat[e] under Iranian command in Syria…with numbers ranging from 24,000–80,000. These figures include not only Lebanese Hezbollah fighters but also Iraqi militias and brigades composed of Afghan and Pakistani Shias.”28
- In 2018, Iran reportedly “command[ed] up to 80,000 fighters in Syria—all members of Shiite militias and paramilitary forces loyal to the leadership in Iran—and [had] effectively secured a land corridor via Iraq and Syria reaching Hezbollah in Lebanon.”29
Working closely with Russia, Iran expanded its military efforts and helped to consolidate a costly victory for the Assad regime. At the height of the fighting in August 2016, Russia temporarily deployed Tu-22M3 bombers and Su-34 strike fighters to an air base at Hamedan in western Iran to strike rebel targets in Syria.30 After the fall of Aleppo in December 2016, which inflicted a crushing defeat on the armed opposition, Tehran sought to entrench a permanent Iranian military presence in Syria, establishing an elaborate infrastructure of military bases, intelligence centers, UAV airfields, missile sites, and logistical facilities. The IRGC also sought to secure a logistical corridor to enable the movement of heavy equipment, arms, and matériel through Iraq and Syria to bolster Hezbollah in Lebanon.
Iran’s military presence in Syria and continued efforts to provide advanced weapons to Hezbollah through Syria have fueled tensions with Israel. Israel has launched more than 2,000 air strikes against Hezbollah and Iranian forces in Syria to prevent the transfer of sophisticated arms and prevent Iran-backed militias from deploying near Israel’s border. On February 10, 2018, Iranian forces in Syria launched an armed drone that penetrated Israeli airspace before being shot down. Israel responded with air strikes on IRGC facilities in Syria. On May 9, 2018, Iranian forces in Syria launched a salvo of 20 rockets against Israeli military positions in the Golan Heights, provoking Israel to launch ground-to-ground missiles, artillery salvos, and air strikes against all known Iranian bases in Syria.31
Although Russia reportedly helped to arrange the withdrawal of Iranian heavy weapons to positions 85 kilometers from Israeli military positions in the Golan Heights, Moscow later “turned a blind eye” to Iranian redeployments and the threat to Israel that deployment of long-range Iranian weapon systems in Syria represents.32 On January 13, 2019, Israel launched an air strike against an Iranian arms depot at Damascus International Airport, and the Israeli government revealed that it had launched over 2,000 missiles at various targets in Syria in 2018.33 Israel remains determined to prevent Iran from establishing forward bases near its borders, and another clash could rapidly escalate into a regional conflict.
By early 2020, Iran reportedly had reduced its military forces in Syria after defeating the rebel military challenge to the Assad regime.34 However, Iran continues to bolster the strength of its proxies and allies in Syria, particularly Hezbollah, which has embedded itself in the Syrian army’s 1st Corps and is recruiting Syrian fighters near the Golan Heights for future attacks on Israel.35 In January 2021, Israel launched a series of air strikes against Iranian forces and proxy militias in eastern Syria, reportedly to prevent Iranian ballistic missiles, cruise missiles, and UAVs that have been deployed in western Iraq from being deployed inside Syria.36
Israel also has targeted Iranian forces and ballistic missiles inside Iraq.37 On March 12, 2022, the IRGC launched up to 12 short range ballistic missiles at a building near Erbil, Iraq, that it claimed was a base used by Israeli intelligence officers.38 The IRGC publicly claimed responsibility for the attack—a rare admission that signals the intensification of the shadow war between Iran and Israel.
Iran’s Proxy Warfare. Iran has adopted a political warfare strategy that emphasizes irregular warfare, asymmetric tactics, and the extensive use of proxy forces. The Islamic Revolutionary Guard Corps has trained, armed, supported, and collaborated with a wide variety of radical Shia and Sunni militant groups as well as Arab, Palestinian, Kurdish, and Afghan groups that do not share its radical Islamist ideology. The IRGC’s elite Quds (Jerusalem) Force has cultivated, trained, armed, and supported numerous proxies, particularly the Lebanon-based Hezbollah; Iraqi Shia militant groups; Palestinian groups such as Hamas and Palestinian Islamic Jihad; and insurgent groups that have fought against the governments of Afghanistan, Bahrain, Egypt, Israel, Iraq, Jordan, Kuwait, Morocco, Saudi Arabia, Turkey, the United Arab Emirates (UAE), and Yemen.
Iran is the world’s foremost state sponsor of terrorism and has made extensive efforts to export its radical Shia brand of Islamist revolution. It has established a network of powerful Shia revolutionary groups in Lebanon and Iraq; has cultivated links with Afghan Shia and Taliban militants; and has stirred Shia unrest in Bahrain, Iraq, Lebanon, Saudi Arabia, and Yemen. In recent years, naval forces have regularly intercepted Iranian arms shipments off the coasts of Bahrain and Yemen, and Israel has repeatedly intercepted Iranian arms shipments, including long-range rockets, bound for Palestinian militants in Gaza.
U.S. troops in the Middle East have been targeted by Iranian proxies in Lebanon in the 1980s, in Saudi Arabia in 1996, and in Iraq since the 2003 overthrow of Saddam Hussein. In April 2019, the Pentagon released an updated estimate of the number of U.S. personnel killed by Iran-backed militias in Iraq, revising the number upward to at least 603 dead between 2003 and 2011. These casualties, about 17 percent of the American death toll in Iraq, “were the result of explosively formed penetrators (EFP), other improvised explosive devices (IED), improvised rocket-assisted munitions (IRAM), rockets, mortars, rocket-propelled grenades (RPG), small-arms, sniper, and other attacks in Iraq” according to a Pentagon spokesman.39
In 2019, Tehran ratcheted up surrogate attacks against U.S. troops in Iraq as part of its aggressive campaign to push back against the U.S. “maximum pressure” sanctions campaign and block the negotiation of a revised nuclear agreement with tighter restrictions. After scores of rocket attacks on Iraqi military bases that hosted U.S. personnel, Iran-controlled Shia militias succeeded in killing an American contractor on December 27, 2019. The ensuing crisis quickly escalated. The U.S. launched air strikes against the Kataib Hezbollah militia that launched the attack; pro-Iranian militia members retaliated by trying to burn down the U.S. embassy in Baghdad; and Washington responded on January 2, 2020, with a drone strike that killed General Qassem Soleimani, leader of the IRGC Quds Force, which was orchestrating the attacks. Iran responded with additional proxy attacks and a ballistic missile attack that failed to kill any U.S. troops stationed at Iraqi military bases.40
After a February 15, 2021, rocket attack on an airport in Erbil, Iraq, killed a U.S. contractor, the U.S. retaliated with air strikes against seven targets inside Syria that were controlled by two Iran-backed Iraqi militias—Kataib Hezbollah and Kataib Sayyid al-Shuhada—that were found to have been responsible for the Erbil attack.41 Attacks by Iran-backed militias have continued in Iraq, including UAV strikes that pose a growing threat to the 2,500 U.S. troops that train and support Iraqi security forces.42
Iran-backed militias also launched attacks against U.S. military forces in Syria, including an October 20, 2021, strike using at least five suicide drones against the small American garrison at Al Tanf. Because of a timely Israeli warning, there were no casualties, but the U.S. failure to respond forcefully to this attack and scores of others has increased the risks to U.S. troops.43 As far back as April 20, 2021, Marine Corps General Kenneth McKenzie, then Commander, United States Central Command, had already warned that Iran’s “small- and medium-sized [unmanned aerial system attacks] proliferating across the [USCENTCOM area of responsibility] present a new and complex threat to our forces and those of our partners and allies. For the first time since the Korean War, we are operating without complete air superiority.”44 Pro-Iranian Iraqi militias also launched a failed drone strike in an attempt to assassinate Iraqi Prime Minister Mustafa al-Kadhimi on November 7, 2021.
Terrorist Threats from Hezbollah. Hezbollah is a close ally of, frequent surrogate for, and terrorist subcontractor for Iran’s revolutionary Islamist regime. Iran played a crucial role in creating Hezbollah in 1982 as a vehicle that it could use to export its revolution, mobilize Lebanese Shia, and develop a terrorist surrogate for attacks on its enemies.
Tehran provides the lion’s share of Hezbollah’s foreign support: arms, training, logistical support, and money. After the nuclear deal, which offered Tehran substantial relief from sanctions, Tehran increased its aid to Hezbollah, providing as much as $800 million per year according to Israeli officials.45 In 2020, the U.S. Department of State estimated that Hezbollah was receiving $700 million a year from Iran.46 Tehran has been lavish in stocking Hezbollah’s expensive and extensive arsenal of rockets, sophisticated land mines, small arms, ammunition, explosives, anti-ship missiles, anti-aircraft missiles, and even UAVs that Hezbollah can use for aerial surveillance or remotely piloted terrorist attacks. Iranian Revolutionary Guards have trained Hezbollah terrorists in Lebanon’s Bekaa Valley and in Iran.
Iran has used Hezbollah as a club to hit not only Israel and Tehran’s Western enemies, but many Arab countries as well. Tehran’s revolutionary ideology has fueled Iran’s hostility to other Middle Eastern governments, many of which it seeks to overthrow and replace with radical allies. During the 1980–1988 Iran–Iraq war, Iran used Hezbollah to launch terrorist attacks against Iraqi targets and against Arab states that sided with Iraq. Hezbollah launched numerous terrorist attacks against Saudi Arabia and Kuwait, which extended strong financial support to Iraq’s war effort, and participated in several other terrorist operations in Bahrain and the UAE.
Iranian Revolutionary Guards conspired with the Saudi Arabian branch of Hezbollah to conduct the 1996 Khobar Towers bombing that killed 19 American military personnel. Hezbollah collaborated with the IRGC’s Quds Force to destabilize Iraq after the 2003 U.S. occupation and helped to train and advise the Mahdi Army, the radical anti-Western Shiite militia led by militant Iraqi cleric Moqtada al-Sadr, as well as other Iraqi militias. Hezbollah detachments also have cooperated with IRGC forces in Yemen to train and assist the Houthi rebel movement.
Hezbollah threatens the security and stability of the Middle East and Western interests in the Middle East on many fronts. In addition to its murderous actions against Israel, Hezbollah has used violence to impose its radical Islamist agenda and subvert democracy in Lebanon. Some experts mistakenly believed that Hezbollah’s participation in the 1992 Lebanese elections and subsequent inclusion in Lebanon’s parliament and coalition governments would moderate its behavior, but political inclusion did not lead it to renounce terrorism.
Hezbollah also poses a potential threat to America’s NATO allies in Europe. It established a presence inside European countries in the 1980s amid the influx of Lebanese citizens who were seeking to escape Lebanon’s civil war and took root among Lebanese Shiite immigrant communities throughout Europe. German intelligence officials have estimated that about 1,250 Hezbollah members and supporters were living in Germany in 2020.47 Hezbollah also has developed an extensive web of fundraising and logistical support cells throughout Europe.48
France and Britain have been the principal European targets of Hezbollah terrorism, partly because both countries opposed Hezbollah’s agenda in Lebanon and were perceived as enemies of Iran, Hezbollah’s chief patron. Hezbollah has been involved in many terrorist attacks against Europeans, including:
- The October 1983 suicide truck bombing of the French contingent of the multinational peacekeeping force in Lebanon, which killed 58 French soldiers on the same day that the U.S. Marine barracks was bombed;
- The April 1985 bombing of a restaurant near a U.S. base in Madrid, Spain, which killed 18 Spanish citizens;
- A campaign of 13 bombings in France in 1986 that targeted shopping centers and railroad facilities, killing 13 people and wounding more than 250; and
- A March 1989 attempt to assassinate British novelist Salman Rushdie that failed when a bomb exploded prematurely, killing a terrorist in London.
Hezbollah’s attacks in Europe trailed off in the 1990s after the group’s Iranian sponsors accepted a truce in their bloody 1980–1988 war with Iraq and no longer needed a surrogate to punish states that Tehran perceived as supporting Iraq. However, if Hezbollah decided to revive its aggressive operations in southern Lebanon, European participation in Lebanese peacekeeping operations, which became a lightning rod for Hezbollah terrorist attacks in the 1980s, could again become an issue. Troops from European Union (EU) member states could someday find themselves attacked by Hezbollah with weapons financed by Hezbollah supporters in their home countries.
Hezbollah operatives have been deployed in countries throughout Europe, including Belgium, Bulgaria, Cyprus, France, Germany, and Greece.49 On April 30, 2020, Germany designated Hezbollah as a terrorist organization after Israel provided intelligence on a stockpile of ammonium nitrate that was stored in a German warehouse and that Hezbollah intended to use to make explosives.
Mounting Missile Threat. Iran “possesses the largest and most diverse missile arsenal in the Middle East.”50 Testifying before the Senate Armed Services Committee in March 2022, General McKenzie estimated that Iran has “over 3,000 ballistic missiles of various types, some of which can reach Tel Aviv, to give you an idea of range. None of them can reach Europe yet, but over the last 5 to 7 years…they have invested heavily in their ballistic missile program.”51
In June 2017, Iran launched mid-range missiles from its territory against opposition targets in Syria. This was Iran’s first such operational use of mid-range missiles in almost 30 years, but it was not as successful as Tehran might have hoped. It was reported that three of the five missiles that were launched missed Syria altogether and landed in Iraq and that the remaining two landed in Syria but missed their intended targets by miles.52
Iran launched a much more successful attack on September 14, 2019, using at least 18 UAVs and three low-flying cruise missiles to destroy parts of the Saudi oil processing facility at Abqaiq and the oil fields at Khurais. The precisely targeted attack shut down half of Saudi Arabia’s oil production, which was approximately equivalent to 5 percent of global oil production. Although Iran denied responsibility, U.S. intelligence sources identified the launch site as the Ahvaz air base in southwest Iran about 650 kilometers north of Abqaiq.53
Iran also used ballistic missiles to attack two Iraqi bases hosting U.S. military personnel on January 8, 2020, in retaliation for an earlier U.S. strike that killed IRGC Quds Force commander General Qassem Soleimani. Of the 16 short-range ballistic missiles launched from three bases inside Iran, 12 reached their targets: 11 struck al-Asad air base in western Iraq, and one struck a base near the northern Iraqi city of Irbil.54 No U.S. personnel were killed, but more than 100 were later treated for traumatic brain injuries.
The backbone of the Iranian ballistic missile force is the Shahab series of road-mobile surface-to-surface missiles. Based on Soviet-designed Scud missiles, the Shahabs are potentially capable of carrying nuclear, chemical, or biological warheads in addition to conventional high-explosive warheads. Their relative inaccuracy (compared to NATO ballistic missiles) limits their effectiveness unless they are employed against large soft targets like cities. Tehran’s heavy investment in such weapons has fueled speculation that the Iranians intend eventually to replace the conventional warheads on their longer-range missiles with nuclear warheads. As noted, Iran is the only country known to have developed missiles with a range of 2,000 kilometers that did not already have a nuclear capability.55
Iran is not a member of the Missile Technology Control Regime. Instead, it has sought aggressively to acquire, develop, and deploy a wide spectrum of ballistic missile, cruise missile, and space launch capabilities. During the Iran–Iraq war, Iran acquired Soviet-made Scud-B missiles from Libya and later acquired North Korean–designed Scud-C and No-dong missiles, which it renamed the Shahab-2 (with an estimated range of 500 kilometers or 310 miles) and Shahab-3 (with an estimated range of 900 kilometers or 560 miles). It now can produce its own variants of these missiles as well as longer-range Ghadr-1 and Qiam missiles.56
Iran’s Shahab-3 and Ghadr-1, which is a modified version of the Shahab-3 with a smaller warhead but greater range (about 1,600 kilometers or 1,000 miles), are considered more reliable and advanced than the North Korean No-dong missile from which they are derived. Although early variants of the Shahab-3 missile were relatively inaccurate, “Iran has employed Chinese guidance technology on later variants to significantly improve strike accuracy.”57 In 2014, then-Defense Intelligence Agency Director Lieutenant General Michael T. Flynn warned that:
Iran can strike targets throughout the region and into Eastern Europe. In addition to its growing missile and rocket inventories, Iran is seeking to enhance [the] lethality and effectiveness of existing systems with improvements in accuracy and warhead designs. Iran is developing the Khalij Fars, an anti-ship ballistic missile which could threaten maritime activity throughout the Persian Gulf and Strait of Hormuz. Iran’s Simorgh space launch vehicle shows the country’s intent to develop intercontinental ballistic missile (ICBM) technology58
Iran’s ballistic missiles threaten U.S. bases and allies from Turkey, Israel, and Egypt to the west to Saudi Arabia and the other Gulf States to the south and Afghanistan and Pakistan to the east. Iran also has become a center for missile proliferation by exporting a wide variety of ballistic missiles, cruise missiles, and rockets to the Assad regime in Syria and such proxy groups as Hezbollah, Hamas, Palestinian Islamic Jihad, the Houthi rebels in Yemen, and Iraqi militias. The Houthi Ansar Allah group has launched hundreds of Iranian-supplied ballistic missiles and armed drones against targets in Saudi Arabia and the UAE, which launched a military campaign against them in 2015 in support of Yemen’s government. On January 24, 2022, the Houthis launched two ballistic missiles at Al Dhafra air base in the UAE, which hosts roughly 2,000 U.S. military personnel who took shelter in security bunkers as the incoming missiles were intercepted by Patriot surface-to-air missiles.59
However, it is Israel, which has fought a shadow war with Iran and its terrorist proxies, that is most at risk from an Iranian missile attack. In case the Israeli government had any doubt about Iran’s implacable hostility, the Revolutionary Guard Corps, which controls most of Iran’s strategic missile systems, displayed a message written in Hebrew on the side of one of the Iranian missiles tested in March 2016: “Israel must be wiped off the earth.”60 The development of nuclear warheads for Iran’s ballistic missiles would significantly degrade Israel’s ability to deter major Iranian attacks (an ability that the existing but not officially acknowledged Israeli nuclear weapons arsenal currently provides).
For Iran’s radical regime, hostility to Israel, which Tehran sometimes calls the “Little Satan,” is second only to hostility to the United States, which the leader of Iran’s 1979 revolution, Ayatollah Khomeini, dubbed the “Great Satan.” However, Iran poses a greater immediate threat to Israel than it does to the United States: Israel is a smaller country, has fewer military capabilities, and is located much closer to Iran and already within range of Iran’s Shahab-3 missiles.
Moreover, all of Israel can be hit with the thousands of shorter-range rockets that Iran has provided to Hezbollah in Lebanon and to Hamas and Palestinian Islamic Jihad in Gaza. In April 2021, Hamas and Palestinian Islamic Jihad launched more than 4,000 rockets and missiles in an 11-day miniwar with Israel.61 Hezbollah, which targeted Israel with more than 4,000 rockets and missiles in the 2006 war, has an arsenal of as many as 150,000 rockets and missiles that it could use to bombard Israel with an estimated 1,500 strikes per day.62 If Iran and Israel escalate their shadow war to a full-scale war, Israel is likely to be attacked by Iranian rockets, missiles, and drones launched not only by Iranian military forces, but also by Iranian proxy groups based in Lebanon, Syria, Gaza, Iraq and Yemen.
Weapons of Mass Destruction. Tehran has invested tens of billions of dollars since the 1980s in a nuclear weapons program that it sought to conceal within its civilian nuclear power program. It built clandestine but subsequently discovered underground uranium enrichment facilities near Natanz and Fordow and a heavy-water reactor near Arak that would generate plutonium to give it a second potential route to nuclear weapons.63
Before the 2015 nuclear deal, Iran had accumulated enough low-enriched uranium to build eight nuclear bombs (assuming that the uranium was enriched to weapon-grade levels). In November 2015, the Wisconsin Project on Nuclear Arms Control reported that “[b]y using the approximately 9,000 first generation centrifuges operating at its Natanz Fuel Enrichment Plant as of October 2015, Iran could theoretically produce enough weapon-grade uranium to fuel a single nuclear warhead in less than 2 months.”64
Clearly, the development of a nuclear bomb would greatly amplify the threat posed by Iran. Even if Iran did not use a nuclear weapon or pass it on to one of its terrorist surrogates to use, the regime could become emboldened to expand its support for terrorism, subversion, and intimidation, assuming that its nuclear arsenal would protect it from retaliation as has been the case with North Korea.
On July 14, 2015, President Barack Obama announced that the United States and Iran, along with China, France, Germany, Russia, the United Kingdom, and the EU High Representative for Foreign Affairs and Security Policy, had reached “a comprehensive, long-term deal with Iran that will prevent it from obtaining a nuclear weapon.”65 The short-lived agreement, however, did a much better job of dismantling sanctions against Iran than it did of dismantling Iran’s nuclear infrastructure, much of which was allowed to remain functional subject to weak restrictions, some of them only temporary. This flaw led President Donald Trump to withdraw the U.S. from the agreement on May 8, 2018, and reimpose sanctions.66
In fact, the agreement did not specify that any of Iran’s covertly built facilities would have to be dismantled. The Natanz and Fordow uranium enrichment facilities were allowed to remain in operation, although the latter facility was to be repurposed at least temporarily as a research site. The heavy-water reactor at Arak was also retained with modifications that would reduce its yield of plutonium. All of these facilities, built covertly and housing operations prohibited by multiple U.N. Security Council resolutions, were legitimized by the agreement.
The Iran nuclear agreement marked a risky departure from more than five decades of U.S. nonproliferation efforts under which Washington opposed the spread of sensitive nuclear technologies such as uranium enrichment even to allies. Iran got a better deal on uranium enrichment under the agreement than such U.S. allies as the UAE, South Korea, and Taiwan have received from Washington in the past. In fact, the Obama Administration gave Iran better terms on uranium enrichment than President Gerald Ford’s Administration gave the Shah of Iran, a close U.S. ally before the 1979 revolution, who was denied independent reprocessing capabilities.
President Trump’s decision to withdraw from the nuclear agreement marked a return to long-standing U.S. nonproliferation policy. Iran, Britain, France, Germany, the EU, China, and Russia sought to salvage the agreement but were unable to offset the strength of U.S. nuclear sanctions that were fully reimposed by November 4, 2018, after a 180-day wind-down period.
Iran initially adopted a policy of “strategic patience,” seeking to preserve as much of the agreement’s relief from sanctions as it could while hoping to outlast the Trump Administration and deal with a more pliable successor Administration after the 2020 elections. The Trump Administration, however, increased sanctions to unprecedented levels under its “maximum pressure” campaign. On April 8, 2019, it designated Iran’s Revolutionary Guards as a foreign terrorist organization. Because the Revolutionary Guards are extensively involved in Iran’s oil, construction, and defense industries, this allowed U.S. sanctions to hit harder at strategic sectors of Iran’s economy.67 On April 22, 2019, Secretary of State Mike Pompeo announced that the Administration would eliminate waivers for Iran’s remaining oil exports on May 2 and seek to zero them out entirely.68
Although President Trump made it clear that he sought a new agreement on Iran’s nuclear program, Tehran refused to return to the negotiating table. Instead, it sought to pressure European states into protecting it from the effects of U.S. sanctions.
On May 8, 2019, Iranian President Rouhani announced that Iran would no longer comply with the 2015 nuclear agreement’s restrictions on the size of Iran’s stockpiles of enriched uranium and heavy water.69 Tehran gave the Europeans 60 days to deliver greater sanctions relief, specifically with respect to oil sales and banking transactions, and warned that if the terms of its ultimatum were not met by July 7, 2019, it would incrementally violate the restrictions set by the JCPOA. Since then, Iran has escalated its noncompliance with the agreement in a series of major violations that include breaching the caps on uranium enrichment, research and development of advanced centrifuges, numbers of operating centrifuges, and resuming enrichment at the fortified Fordow facility. When announcing the fifth breach in January 2020, Iran stated that its uranium enrichment program no longer faced any restrictions.70
By February 2021, Iran had accumulated about 4,390 kilograms of low-enriched uranium and had reduced its estimated breakout time (the time needed to produce enough weapon-grade uranium for one nuclear weapon) to as little as 2.7 months with enough enriched uranium to arm three nuclear weapons within six months if it continued to enrich to higher levels.71 In April 2021, Iran began to enrich its uranium to 60 percent, a short step away from the weapon-grade level of 90 percent. By June 2022, Iran’s breakout time had fallen to zero. It had acquired enough highly enriched uranium to arm a bomb within weeks if further enriched and could acquire enough for five bombs within six months.72
Although Tehran has not enriched to weapon-grade levels so far, it essentially has become a threshold nuclear power and seeks to leverage that status to gain additional concessions from the U.S. at the multilateral nuclear negotiations in Vienna, Austria. Those talks, begun in April 2021, had been frozen since March 2022, largely because of Iran’s insistence that it gain sanctions relief for the IRGC, which Washington has designated as a foreign terrorist organization. Two days of new “last-gasp talks,” facilitated by representatives from the European Union, were attempted in Doha in June 2022 but ended abruptly when disputes about sanctions and Iran’s request for a guarantee that no future U.S. government would seek to withdraw from the agreement could not be resolved.73
Iran’s accelerating nuclear program prompted Israel to step up its covert efforts to sabotage Iran’s nuclear progress. Israel had worked with the U.S. to sabotage Iran’s centrifuge operations with the Stuxnet virus cyberattacks before the 2015 agreement and had unilaterally launched operations to assassinate Iranian nuclear scientists.
Israel paused the assassination campaign during the runup to the 2015 nuclear agreement but then escalated its covert efforts after the 2018 U.S. withdrawal from the agreement. Iran’s top nuclear scientist, Mohsen Fakhrizadeh, was killed by a remote-controlled machine gun on November 27, 2020.74 On April 11, 2021, Iran’s uranium enrichment efforts were disrupted by an explosion that cut power and damaged centrifuges at the underground Natanz enrichment facility, an incident that Tehran attributed to Israeli sabotage.75 Israel also launched sabotage and drone attacks against Iran’s ballistic missile and drone facilities and expanded covert attacks inside Iran to include the May 22, 2022, assassination of Colonel Hassan Sayyad Khodaei, the head of the IRGC unit that targeted Israelis for terrorist attacks. The expanded attacks on non-nuclear targets reportedly were executed as part of Israel’s new “Octopus Doctrine” in which Israel seeks to retaliate for Iranian proxy attacks by targeting the head of the octopus rather than its tentacles.76
Iran also is a declared chemical weapons power that used chemical weapons in its war against Iraq after the Iraqis conducted chemical attacks. Tehran claims to have destroyed all of its stockpiles of chemical weapons, but it has never fully complied with the Chemical Weapons Convention or declared its holdings.77 U.S. intelligence agencies have assessed that Iran maintains “the capability to produce chemical warfare (CW) agents and ‘probably’ has the capability to produce some biological warfare agents for offensive purposes, if it made the decision to do so.”78
Iranian Threats to Israel. In addition to ballistic missile threats from Iran, Israel faces the constant threat of attack from Palestinian, Lebanese, Egyptian, Syrian, and other Arab terrorist groups, including many that are supported by Iran. The threat posed by Arab states, which lost four wars against Israel in 1948, 1956, 1967, and 1973 (Syria and the PLO lost a fifth war in 1982 in Lebanon), has gradually declined. Egypt, Jordan, the UAE, Bahrain, and Morocco have signed peace treaties with Israel, and Iraq, Libya, Syria, and Yemen have been distracted by civil wars. At the same time, however, unconventional military and terrorist threats from an expanding number of substate actors have risen substantially.
Iran has systematically bolstered many of these groups, including some whose ideology it does not necessarily share. Today, for example, Iran’s surrogates Hezbollah and Palestinian Islamic Jihad, along with more distant ally Hamas, pose the chief immediate security threats to Israel. After Israel’s May 2000 withdrawal from southern Lebanon and the September 2000 outbreak of fighting between Israelis and Palestinians, Hezbollah stepped up its support for such Palestinian extremist groups as Hamas, Palestinian Islamic Jihad, the al-Aqsa Martyrs’ Brigades, and the Popular Front for the Liberation of Palestine. It also expanded its own operations in the West Bank and Gaza and provided funding for specific attacks launched by other groups.
In July 2006, Hezbollah forces crossed the Lebanese border to kidnap Israeli soldiers inside Israel, igniting a military clash that claimed hundreds of lives and severely damaged the economies on both sides of the border. Hezbollah has since rebuilt its depleted arsenal with help from Iran and Syria and has amassed at least 130,000 rockets and missiles—more than all of the European members of NATO combined.79 Some of the most dangerous are long-range Iranian-made missiles capable of striking cities throughout Israel.80 In recent years, under cover of the war in Syria, Iran has provided Hezbollah with increasingly sophisticated, accurate, and longer-range weapons as well as guidance kits that upgrade the accuracy of older rockets.81 Iran and Hezbollah also have established another potential front against Israel in Syria.
Since Israel’s withdrawal from the Gaza Strip in 2005, Hamas, Palestinian Islamic Jihad, and other terrorist groups have fired more than 11,000 rockets into Israel during brief wars in 2008–2009, 2012, and 2014.82 More than 5 million Israelis out of a total population of 8.1 million live within range of rocket attacks from Gaza, although the successful operation of the Iron Dome anti-missile system has greatly mitigated this threat in recent years. In the 2014 Gaza war, Hamas also unveiled a sophisticated tunnel network that it used to infiltrate Israel so that it could launch attacks on Israeli civilians and military personnel.
In early May 2019, Palestinian Islamic Jihad ignited another round of fighting in Gaza during which “Hamas and other groups fired about 700 rockets into Israel on May 4 alone—for comparison, in 2014 they fired fewer than 200 rockets per day.”83 In May 2021, Hamas and Palestinian Islamic Jihad launched another 11-day war during which they fired about 4,300 rockets at Israel, killing 12 Israelis while suffering more than 240 Palestinian deaths, including roughly 200 militants, according to Israel.84 Gaza remains a flash point that could trigger another conflict with little warning.
Threats to Saudi Arabia and Other Members of the Gulf Cooperation Council. In 1981, Saudi Arabia and the five other Arab Gulf States—Bahrain, Kuwait, Oman, Qatar, and the UAE—formed the Gulf Cooperation Council (GCC) to deter and defend against Iranian aggression. Iran remains the primary external threat to their security. Tehran has supported groups that launched terrorist attacks against Bahrain, Iraq, Kuwait, Saudi Arabia, and Yemen.
Iran sponsored the Islamic Front for the Liberation of Bahrain, a surrogate group that plotted a failed 1981 coup against Bahrain’s ruling Al Khalifa family, the Sunni rulers of the predominantly Shia country. Iran also has long backed Bahraini branches of Hezbollah and the Dawa Party. When Bahrain was engulfed in a wave of Arab Spring protests in 2011, its government charged that Iran again exploited the protests to back the efforts of Shia radicals to overthrow the royal family. Saudi Arabia, fearing that a Shia revolution in Bahrain would incite its own restive Shia minority, led a March 2011 GCC intervention that backed Bahrain’s government with about 1,000 Saudi troops and 500 police from the UAE.
Bahrain has repeatedly intercepted shipments of Iranian arms, including sophisticated bombs employing explosively formed penetrators. The government withdrew its ambassador to Tehran when two Bahrainis with ties to the IRGC were arrested after their arms shipment was intercepted off Bahrain’s coast in July 2015.
Iranian hard-liners have steadily escalated their pressure on Bahrain. In March 2016, a former IRGC general who is a close adviser to Ayatollah Khamenei stated that “Bahrain is a province of Iran that should be annexed to the Islamic Republic of Iran.”85 After Bahrain stripped a senior Shiite cleric, Sheikh Isa Qassim, of his citizenship, General Qassim Suleimani, commander of the IRGC’s Quds Force, threatened to make Bahrain’s royal family “pay the price and disappear.”86
Saudi Arabia has criticized Iran for supporting radical Saudi Shiites, intervening in Syria, and supporting Shiite Islamists in Lebanon, Iraq, and Yemen. In January 2016, Saudi Arabia executed a Shiite cleric charged with sparking anti-government protests and cut diplomatic ties with Iran after Iranian mobs responded to the execution by attacking and setting fire to the Saudi embassy in Tehran.87
In addition to military threats from Iran, Saudi Arabia and the other GCC states face terrorist threats and possible rebellions by Shia or other disaffected internal groups supported by Tehran. Iran has backed Shiite terrorist groups against Saudi Arabia, Bahrain, Iraq, and Kuwait and has supported the Shiite Houthi rebels in Yemen. In March 2015, Saudi Arabia led a 10-country coalition that launched a military campaign against Houthi forces and provided support for ousted Yemeni President Abdu Rabu Mansour Hadi, who took refuge in Saudi Arabia. The Saudi Navy also established a blockade of Yemeni ports to prevent Iran from aiding the rebels.
The Houthis have retaliated by launching Iranian-supplied missiles at military and civilian targets in Saudi Arabia and the UAE, including ballistic missile attacks on airports, Riyadh, and other cities as well as cruise missile strikes. In December 2017, the Houthis launched a cruise missile attack on an unfinished nuclear reactor in Abu Dhabi.
The Houthis also have made extensive use of UAVs and UCAVs (unmanned combat aerial vehicles, or armed drones). A Houthi UCAV attacked a military parade in Yemen in January 2019, killing at least six people including Yemen’s commander of military intelligence, and longer-range UCAVs were used in a coordinated attack on Saudi Arabia’s East–West pipeline on May 14, 2019.88 The Houthis have employed Iranian Sammad-2 and Sammad-3 UCAVs in strikes against Riyadh, Abu Dhabi International Airport in the UAE, and other targets.89
In addition, the Houthis have steadily increased their attacks. During the first nine months of 2021, Houthi attacks against Saudi Arabia averaged 78 a month, more than double the number from the same period in 2020 when the average was 38 per month.90 A cease-fire reached in April 2022 to allow negotiations has reduced the scale of the fighting in Yemen, but cross-border attacks could resume if peace negotiations break down.
Threats to the Commons
The United States has critical interests at stake in the Middle Eastern commons: sea, air, space, and cyber. The U.S. has long provided the security backbone in these areas, and this security has supported the region’s economic development and political stability.
Sea. Maintaining the security of the sea lines of communication in the Persian Gulf, Arabian Sea, Red Sea, and Mediterranean Sea is a high priority for strategic, economic, and energy security purposes. “In 2021,” according to the U.S. Energy Administration, “the seven countries in the Persian Gulf produced about 30% of total world crude oil, and they held about 48% of world proved crude oil reserves at the start of 2020.”91 The Persian Gulf is a crucial source of oil and gas for energy-importing states, particularly China, India, Japan, South Korea, and many European countries. Interstate conflict or terrorist attacks could easily interrupt the flow of that oil.
Bottlenecks such as the Strait of Hormuz, Suez Canal, and Bab el-Mandeb Strait are potential choke points for restricting the flow of oil, international trade, and the deployment of U.S. and allied naval forces. Although the United States has reduced its dependence on oil exports from the Gulf, it still would sustain economic damage in the event of a spike in world oil prices, and many of its European and Asian allies and trading partners import a substantial portion of their oil needs from the region.
The world’s most important maritime choke point and the jugular vein through which most Gulf oil exports flow to Asia and Europe is the Strait of Hormuz. In 2018, the “daily oil flow [through the Strait of Hormuz] averaged 21 million barrels per day (b/d), or the equivalent of about 21% of global petroleum liquids consumption.”92 The chief potential threat to the free passage of ships through the strait is Iran, whose Supreme Leader, Ayatollah Ali Khamenei, proclaimed in 2006 that “[i]f the Americans make a wrong move toward Iran, the shipment of energy will definitely face danger, and the Americans would not be able to protect energy supply in the region.”93
Iranian officials often reiterate these threats during periods of heightened tension. For example, the chief of staff of Iran’s army, Major General Mohammad Baqeri, warned on April 28, 2019, that “if our oil does not pass, the oil of others shall not pass the Strait of Hormuz either.”94 Less than one month later, Iran began to intensify its intimidation tactics against international shipping near the strait.
On May 12, 2019, four oil tankers were damaged by mysterious explosions off the coast of the UAE in the Gulf of Oman. Then-U.S. National Security Adviser John Bolton stated that it was “naval mines almost certainly from Iran” that caused the damage.95 On June 13, two more tankers were attacked in the Gulf of Oman. Even though Iranian Revolutionary Guards were filmed removing an unexploded limpet mine from one of the damaged ships, Tehran continued to deny its involvement in all of the attacks.96 On June 19, an IRGC surface-to-air missile shot down a U.S. surveillance drone in international air space. The U.S. initially planned to launch retaliatory strikes, but President Trump called off the operation.97 In September, Iran continued its aggressive behavior by launching a sophisticated UCAV and cruise missile attack on Saudi oil facilities.
Then, in late 2019, Iranian-controlled Iraqi militias launched a series of rocket attacks on Iraqi bases containing U.S. troops, provoking U.S. retaliatory air strikes against those militias and the January 2020 UCAV strike that killed General Qassem Soleimani. Rocket attacks by Iraqi militias have continued, and tensions remain high in Gulf waters.
On May 10, 2020, a missile launched from an Iranian Navy frigate struck another Iranian naval vessel during a military exercise in the Gulf of Oman, killing at least 19 sailors and wounding 15.98 The incident raised questions about the competence and training of Iran’s naval forces. The June 2, 2021, sinking of the Kharg, Iran’s largest warship, raised similar questions. The Kharg, a naval replenishment ship, caught fire and sank in the Gulf of Oman during a training exercise. Iran sustained another setback when its newest frigate, the Talayieh, capsized in its dry dock on December 5, 2021.
However, while Iran’s military forces have suffered numerous accidents because of lax maintenance and safety practices, there also was speculation that some of the incidents may have resulted from covert Israeli attacks. Israel reportedly has attacked at least 12 Iranian vessels transporting oil, arms, and other cargo to Syria to prop up the Assad regime and Hezbollah.99 It also has been suspected of triggering the April 6, 2021, explosion that damaged the Saviz, a converted cargo ship permanently moored in the Red Sea near the coast of Yemen to collect intelligence and support Iran’s Houthi allies.100 For its part, Iran is suspected of at least two attacks on Israeli-owned cargo ships: one on February 25, 2021, in the Gulf of Oman and another on March 25, 2021, in the Arabian Sea.101 Although its contours remain murky, it is clear that the Iran–Israel shadow war has expanded to include maritime attacks.
Iran has a long history of attacking oil shipments in the Gulf. During the Iran–Iraq war, each side targeted the other’s oil facilities, ports, and oil exports. Iran escalated attacks to include neutral Kuwaiti oil tankers and terminals and clandestinely laid mines in Persian Gulf shipping lanes while its ally Libya clandestinely laid mines in the Red Sea. The United States defeated Iran’s tactics by reflagging Kuwaiti oil tankers, clearing the mines, and escorting ships through the Persian Gulf, but several commercial vessels were damaged during the so-called Tanker War from 1984 to 1987.
Iran’s demonstrated willingness to disrupt oil traffic through the Persian Gulf to pressure Iraq economically is a red flag to U.S. military planners. During the 1980s Tanker War, Iran’s ability to strike at Gulf shipping was limited by its aging and outdated weapons systems and the arms embargo imposed by the U.S. after the 1979 revolution. Since the 1990s, however, Iran has been upgrading its military with new weapons from North Korea, China, and Russia in addition to domestically manufactured weapons.
Since the Iran–Iraq war, Tehran has invested heavily in developing its naval forces, particularly the IRGC Navy, along unconventional lines. Today, Iran boasts an arsenal of Iranian-built missiles based on Russian and Chinese designs that represent significant threats to oil tankers as well as warships. Iran has deployed mobile anti-ship missile batteries along its 1,500-mile Gulf coast and on many of the 17 Iranian-controlled islands in the Gulf in addition to modern anti-ship missiles mounted on fast attack boats, submarines, oil platforms, and vessels disguised as civilian fishing boats. Six of Iran’s 17 islands in the Gulf—Forur, Bani Forur, Sirri, and three islands seized from the UAE: Abu Musa, Greater Tunb, and Lesser Tunb—are particularly important because they are located close to the shipping channels that all ships must use near the Strait of Hormuz.
Iran has imported Russian submarines, North Korean minisubmarines, and a wide variety of advanced Chinese anti-ship missiles. It also has a significant stock of Chinese-designed anti-ship cruise missiles, including the older HY-2 Seersucker and the more modern CSS-N-4 Sardine and CSS-N-8 Saccade models, and has reverse engineered Chinese missiles to produce its own Ra’ad and Noor anti-ship cruise missiles. More recently, Tehran has produced and deployed more advanced anti-ship cruise missiles, the Nasir and Qadir.102 Shore-based missiles deployed along Iran’s coast would be augmented by aircraft-delivered laser-guided bombs and missiles as well as by television-guided bombs.
Iran has a large supply of anti-ship mines, including modern mines that are far superior to the simple World War I–style contact mines that it used in the 1980s. In addition to expanding the quantity of its mines from an estimated 1,500 during the Iran–Iraq war to more than 5,000 in 2019, Tehran has increased their quality.103 It has acquired significant stocks of “smart mines” including versions of the Russian MDM-6, Chinese MC-52, and Chinese EM-11, EM-31, and EM-55 mines.104 One of Iran’s most lethal mines is the Chinese-designed EM-52 “rocket” mine, which remains stationary on the sea floor and fires a homing rocket when a ship passes overhead.
Iran can deploy mines or torpedoes from its three Kilo-class submarines, purchased from Russia and based at Bandar Abbas, Iran’s largest seaport and naval base. These submarines could be difficult to detect for brief periods when running silent and remaining stationary on a shallow bottom just outside the Strait of Hormuz.105 Iran also could use minisubmarines, helicopters, or small boats disguised as fishing vessels to deploy its mines. Iran’s robust mine warfare capability and the U.S. and allied navies’ limited capacity for countermine operations are major challenges to Gulf maritime security.106
Iran has developed two separate naval forces. The regular navy takes the lead in the Caspian Sea and outside the Strait of Hormuz in the Gulf of Oman, and the Islamic Revolutionary Guard Corps Navy is Iran’s dominant force inside the Persian Gulf. The IRGC Navy has developed an effective asymmetric naval warfare strategy that could enable it to counter the superior firepower and technology of the U.S. Navy and its GCC allies, at least for a short period. It has adopted swarming tactics using well-armed fast attack boats to launch surprise attacks against larger and more heavily armed naval adversaries.
The commander of the IRGC Navy bragged in 2008 that it had brought guerilla warfare tactics to naval warfare: “We are everywhere and at the same time nowhere.”107 The IRGC has honed such unconventional tactics as deploying remote-controlled radar decoy boats and boats packed with explosives to confuse defenses and attack adversaries. It also could deploy naval commandos trained to attack using small boats, minisubmarines, and even Jet Skis as well as underwater demolition teams that could attack offshore oil platforms, moored ships, ports, and other facilities.
On April 28, 2015, the Revolutionary Guard naval force seized the Maersk Tigris, a container ship registered in the Marshall Islands, near the Strait of Hormuz. Tehran claimed that it seized the ship because of a previous court ruling ordering the Maersk Line, which charters the ship, to make a payment to settle a dispute with a private Iranian company. The ship was later released after being held for more than a week.108 Then, on May 14, 2015, the Alpine Eternity, a Singapore-flagged oil tanker, was surrounded and attacked by Revolutionary Guard gunboats in the Strait of Hormuz when it refused to be boarded. Iranian authorities alleged that it had damaged an Iranian oil platform in March, but the ship’s owners maintained that it had hit an uncharted submerged structure.109
The Revolutionary Guard’s aggressive tactics in using commercial disputes as pretexts for illegal seizures of transiting vessels prompted the U.S. Navy to escort American and British-flagged ships through the Strait of Hormuz for several weeks in May 2015 before tensions eased. Iran again resorted to pirate tactics when it seized two Greek tankers on May 27, 2022, in retaliation for Greece’s seizure of an Iranian oil tanker in April 2022.110
The July 2015 nuclear agreement did not alter the Revolutionary Guard’s confrontational tactics in the Gulf.111 IRGC naval forces have challenged U.S. naval forces in a series of incidents. IRGC missile boats launched rockets within 1,500 yards of the carrier Harry S. Truman near the Strait of Hormuz in late December 2015,112 have flown drones over U.S. warships,113 and detained and humiliated 10 American sailors in a provocative January 12, 2016, incident.114 Even though the two U.S. Navy boats carrying the sailors had drifted inadvertently into Iranian territorial waters and had the right of innocent passage, their crews were disarmed, forced onto their knees, filmed, and exploited in propaganda videos.
In 2017, for unknown reasons, Iran temporarily halted the harassment of U.S. Navy ships. According to U.S. Navy reports, Iran instigated 23 “unsafe and/or unprofessional” interactions with U.S. Navy ships in 2015, 35 in 2016, and 14 in the first eight months of 2017 with the last incident occurring on August 14, 2017.115 The provocations resumed in April 2020 when 11 IRGC Navy gunboats harassed six U.S. Navy vessels that were conducting exercises in the international waters of the North Arabian Gulf.116 One week later, President Trump warned that U.S. Navy forces were authorized to destroy any Iranian vessels that harassed them. Iran’s naval harassment subsided for a time but resumed in April 2021 when the IRGC Navy staged two incidents, forcing U.S. naval vessels to take evasive action in the first and fire warning shots in the second.117
Iran has been accused of spoofing satellite navigation systems to lure foreign ships into its territorial waters so that it can seize them. This may have occurred in 2016 when 10 U.S. sailors were captured near an Iranian island and in 2019 when the Stena Impero tanker was seized in the Strait of Hormuz.118 Iran also may have used a similar technique to divert a U.S. UAV from Afghan airspace to Iran where it was captured and put on display in 2011.
If Tehran were to attack ships transiting the Strait of Hormuz, the United States and its allies have the capacity to counter Iran’s maritime threats and restore the flow of oil exports, but “the effort would likely take some time—days, weeks, or perhaps months—particularly if a large number of Iranian mines need to be cleared from the Gulf.”119 In May 2019, naval warfare experts estimated that by using its combined coastal missile batteries, mines, submarines, and naval forces, Iran could close the strait for up to four weeks.120 Such an aggressive move would be very costly and risky for Tehran. Closing the strait would also block Iran’s oil exports and many of its imports, including imports of food and medicine. Moreover, most of Iran’s naval forces, naval bases, and other military assets could be destroyed in the resulting conflict.
In addition to using its own forces, Tehran could use its extensive network of clients in the region to sabotage oil pipelines and other infrastructure or to strike oil tankers in port or at sea. Iranian Revolutionary Guards deployed in Yemen reportedly played a role in the unsuccessful October 9 and 12, 2016, missile attacks launched by Houthi rebels against the USS Mason, a U.S. Navy warship, near the Bab el-Mandeb Strait in the Red Sea.121 The Houthis denied that they launched the missiles, but they did claim responsibility for an October 1, 2016, attack on a UAE naval vessel and the February 2017 suicide boat bombing of a Saudi warship. On January 3, 2022, Houthi naval forces seized a UAE freighter in the Red Sea off Yemen’s west coast.
Houthi irregular forces have deployed mines along Yemen’s coast, used a remote-controlled boat packed with explosives in an unsuccessful July 2017 attack on the Yemeni port of Mokha, and have launched several unsuccessful naval attacks against ships in the Red Sea. Houthi gunboats also attacked and damaged a Saudi oil tanker near the port of Hodeidah on April 3, 2018.
U.N. investigators have concluded that the Houthis also operate UAVs with a range of up to 1,500 kilometers (930 miles), several of which were used to attack Saudi Arabia’s East–West pipeline on May 14, 2019.122 This attack and attacks on oil tankers in the Gulf of Oman two days earlier were likely a signal from Tehran that it can also disrupt oil shipments outside the Persian Gulf in a crisis. The Houthis have staged numerous UCAV attacks on Saudi targets along with a cruise missile attack on June 12, 2019, and an attack by 10 ballistic missiles on August 25, 2019.123 The Houthis also claimed responsibility for the September 14, 2019, attacks on Saudi oil facilities at Abqaiq, but U.S. officials asserted that intelligence reports identified Iran as the staging ground for the attacks.124 On March 7, 2021, the Houthis launched long-range UAVs and ballistic missiles provided by Iran at Saudi Arabia’s Ras Tanura oil shipment facility, which is the world’s largest, driving oil prices up to over $70 per barrel for the first time since the COVID-19 pandemic depressed the global economy.125
Air. The Middle East is particularly vulnerable to attacks on civilian aircraft. Large quantities of arms, including man-portable air defense systems, were looted from arms depots in Libya, Iraq, Syria, and Yemen during their civil wars and could be in the hands of Iranian-supported groups. Iran has provided anti-aircraft missiles to Hezbollah, Iraqi militias, and the Houthi rebels in Yemen. The Houthis also have attacked Saudi airports with ballistic missiles and armed drones, although they may have been targeting nearby military facilities.126
Perhaps the greatest Iranian threat to civil aviation would come in the event of a military clash in the crowded skies over the Persian Gulf. On May 16, 2019, during a period of heightened tensions with Iran, the U.S. Federal Aviation Administration warned commercial airlines that civilian planes risked being targeted by the Iranian military as a result of “miscalculation or misidentification.”127
Tragically, this warning foreshadowed the January 8, 2020, shooting down of Ukraine International Airlines Flight 752 that killed 176 passengers and crew, most of them Iranians. Several hours earlier, Iran had launched a ballistic missile attack on Iraqi bases hosting U.S. troops, and Iranian officials later admitted that they had kept Tehran’s airport open in the hope that the presence of passenger jets could act as a deterrent against an American attack on the airport or a nearby military base.128
Space. Iran has launched satellites into orbit, but there is no evidence that it has an offensive space capability. Tehran successfully launched three satellites in February 2009, June 2011, and February 2012 using the Safir space launch vehicle, which uses a modified Ghadr-1 missile for its first stage and has a second stage that is based on the obsolete Soviet R-27 submarine-launched ballistic missile.129 The technology probably was transferred by North Korea, which built its BM-25 missiles using the R-27 as a model.130 Safir technology could be used to develop long-range ballistic missiles.
In December 2013, Iran claimed that it had “sent a monkey into space for the second time, representing the nation’s latest step toward sending humans into space.”131 Tehran also announced in June 2013 that it had established its first space tracking center to monitor objects in “very remote space” and help manage the “activities of satellites.”132 On July 27, 2017, Iran tested a Simorgh (Phoenix) space launch vehicle that it claimed could place a satellite weighing up to 250 kilograms (550 pounds) in an orbit of 500 kilometers (311 miles).133 The satellite launch failed, as did another Simorgh-boosted satellite launch in January 2019.134
In April 2020, Tehran finally discarded the pretense that its space program was dedicated exclusively to peaceful purposes. On April 22, Iran’s Revolutionary Guards launched a Noor (Light) satellite into a low Earth orbit from a secret missile base to celebrate the 41st anniversary of the IRGC’s founding. The spy satellite’s path takes it over North Africa and the central Mediterranean, putting Israel within its potential field of vision approximately every 90 minutes.135 General Jay Raymond, Commander, U.S. Space Command, dismissed the satellite as a “tumbling webcam in space,”136 but Iran’s real achievement focused more on the previously unheard-of satellite carrier, the Qased (Messenger), a three-stage system that used both solid and liquid fuel.137 The technical advances required to launch a satellite are similar to those required to launch an ICBM, and the use of solid fuel could allow Iran to launch a missile more quickly—something that is crucial in an offensive weapon.
On February 2, 2021, Iran’s Defense Ministry announced the successful development of a new satellite launch vehicle, the Zuljanah. The first two stages of the three-stage rocket use solid fuel, and the rocket can be launched from a mobile launch pad—two characteristics that are more suitable for a weapons system than for a satellite launch system.138 In February 2022, a Zuljanah launch vehicle apparently blew up on a launch pad at the Imam Khomeini Spaceport.139 Despite frequent failures, Iran’s satellite launches have been criticized by the United States and other countries for defying a U.N. Security Council resolution calling on Tehran to undertake no activity related to ballistic missiles that are capable of delivering nuclear weapons.
Cyber. Iranian cyber capabilities present a significant threat to the U.S. and its allies. Iran has developed offensive cyber capabilities as a tool of espionage and sabotage and claims “to possess the ‘fourth largest’ cyber force in the world—a broad network of quasi-official elements, as well as regime-aligned ‘hacktivists,’ who engage in cyber activities broadly consistent with the Islamic Republic’s interests and views.”140
The creation of the Iranian Cyber Army in 2009 marked the beginning of a cyber offensive against those whom the Iranian regime regards as enemies. The Ajax Security Team, a hacking group believed to be operating out of Iran, has used malware-based attacks to target U.S. defense organizations and has breached the Navy Marine Corps Intranet.141 The group also has targeted dissidents within Iran, seeding versions of anti-censorship tools with malware and gathering information about users of those programs.142 Iran has invested heavily in cyber activity, reportedly spending “over $1 billion on its cyber capabilities in 2012 alone.”143
An April 2015 study released by the American Enterprise Institute reported that hostile Iranian cyber activity had increased significantly since the beginning of 2014 and could threaten U.S. critical infrastructure. The Islamic Revolutionary Guard Corps and Sharif University of Technology are two Iranian institutions that investigators have linked to efforts to infiltrate U.S. computer networks.144
Iran allegedly has used cyber weapons to engage in economic warfare, most notably the sophisticated and debilitating “[distributed] denial-of-service (DDoS) attacks against a number of U.S. financial institutions, including the Bank of America, JPMorgan Chase, and Citigroup.”145 In February 2014, Iran launched a crippling cyberattack against the Sands Casino in Las Vegas, owned by Sheldon Adelson, a leading supporter of Israel and critic of the Iranian regime.146 In 2012, Tehran was suspected of launching both the Shamoon virus attack on Saudi Aramco, the world’s largest oil-producing company—an attack that destroyed approximately 30,000 computers—and an attack on Qatari natural gas company Rasgas’s computer networks.147
Israel has been a major target of Iranian cyberattacks. In 2014, Iranian hackers launched denial-of-service attacks against the infrastructure of the Israel Defense Forces. On April 24, 2020, an Iranian cyberattack targeted the command and control center of Israel’s Water Authority, disrupting operations of Israeli water and sewage facilities. According to an Israeli cyber expert, the operation was “a first-of-its-kind attack and they were not far from inflicting human casualties.”148 Israel retaliated with a May 9, 2020, cyberattack that disrupted operations at one of Iran’s most important port facilities, the Shahid Rajaee terminal in Bandar Abbas.149 In September 2020, according to the Israeli cybsersecurity company Clearsky, a hacker group linked to Iran targeted “many prominent Israeli organizations.” The group, named MuddyWater, used malware disguised as ransomware that would encrypt files and demand payment but not allow the files to be accessed.150
In the fall of 2015, U.S. officials warned of a surge of sophisticated Iranian computer espionage that would include a series of cyberattacks against State Department officials.151 In March 2016, the Justice Department indicted seven Iranian hackers for penetrating the computer system that controlled a dam in the State of New York.152 In April 2020, Iran-linked hackers targeted staff at the World Health Organization and the U.S. pharmaceutical company Gilead Sciences Inc., a leader in developing a treatment for the COVID-19 virus.153 FBI Director Christopher Wray revealed in a June 1, 2022, speech in Boston that the FBI had thwarted an attempted Iranian government-sponsored cyberattack on Boston Children’s Hospital in the summer of 2021, characterizing Iran’s action as “one of the most despicable cyberattacks I’ve ever seen.”154
The growing sophistication of these and other Iranian cyberattacks, together with Iran’s willingness to use these weapons, has led various experts to characterize Iran as one of America’s most cyber-capable opponents. Russia reportedly “has helped Iran become a cyber-power by supplying it with cyber weapons, information, and capabilities. In turn, Iran passed its expertise to its terrorist proxy Hizballah.”155 Iranian cyber forces have gone so far as to create fake online personas in order to extract information from U.S. officials through such accounts as LinkedIn, YouTube, Facebook, and Twitter.156
Significantly, the FBI sent the following cyber alert to American businesses on May 22, 2018:
The FBI assesses [that] foreign cyber actors operating in the Islamic Republic of Iran could potentially use a range of computer network operations—from scanning networks for potential vulnerabilities to data deletion attacks—against U.S.-based networks in response to the U.S. government’s withdrawal from the Joint Comprehensive Plan of Action (JCPOA).157
On November 4, 2020, the U.S. Department of Justice announced that it had seized 27 domain names used by Iran’s IRGC in a global covert influence campaign.158 A National Intelligence Council report released on March 16, 2021, assessed that during the 2020 U.S. presidential election:
Iran carried out a multi-pronged covert influence campaign intended to undercut former President Trump’s reelection prospects—though without directly promoting his rivals—undermine public confidence in the electoral process and US institutions, and sow division and exacerbate societal tensions in the US.159
Iran’s election influence efforts were primarily focused on sowing discord in the United States and exacerbating societal tensions—including by creating or amplifying social media content that criticized former President Trump—probably because they believed that this advanced Iran’s longstanding objectives and undercut the prospects for the former President’s reelection without provoking retaliation.160
Iran represents by far the most significant security challenge to the United States, its allies, and its interests in the greater Middle East. Its open hostility to the United States and Israel, sponsorship of terrorist groups, and history of threatening the commons underscore the problem. Today, Iran’s provocations are mostly a concern for the region and America’s allies, friends, and assets there. Iran relies heavily on irregular (to include political) warfare against others in the region and fields more ballistic missiles than any of its neighboring countries field. The development of its ballistic missiles and potential nuclear capability also mean that it poses a significant long-term threat to the security of the U.S. homeland.
This Index therefore assesses the overall threat from Iran, considering the range of contingencies, as “aggressive.” Iran’s capability score holds at “gathering.”161
 Rebecca Leung, “Hezbollah: ‘A-Team of Terrorists,’” CBS News, 60 Minutes, April 18, 2003, http://www.cbsnews.com/news/hezbollah-a-team-of-terrorists/ (accessed June 28, 2022).
 Dana Priest and Nora Boustany, “Buckley’s Remains Identified,” The Washington Post, December 28, 1991, https://www.washingtonpost.com/archive/politics/1991/12/28/buckleys-remains-identified/5b3bf0cc-41c2-4a1c-aa0b-27be8c3795d2/ (accessed June 28, 2022).
 Suzanne Kelly, “Experts: Hezbollah Positioned for Attack in U.S.,” CNN, March 21, 2012, http://security.blogs.cnn.com/2012/03/21/house-panel-hears-testimony-on-hezbollah-in-u-s/ (accessed June 28, 2022).
 Ellie Kaufman, “2 Americans Led Double Lives as Hezbollah Agents, Officials Say,” CNN, updated June 9, 2017, http://www.cnn.com/2017/06/08/us/americans-accused-hezbollah-agents/ (accessed June 28, 2022).
 Nathan A. Sales, Ambassador-at-Large and Coordinator for Counterterrorism, and Nicholas J. Rasmussen, National Counterterrorism Center Director, “Briefing on U.S. Efforts to Counter Hizballah,” U.S. Department of State, October 10, 2017, https://2017-2021.state.gov/briefing-on-u-s-efforts-to-counter-hizballah/index.html (accessed June 28, 2022).
 Jason Hanna, Elizabeth Joseph, and Brynn Gingras, “A New Jersey Man Scouted US Landmarks for Potential Hezbollah Attacks, Charges Allege,” CNN, September 20, 2019, https://www.cnn.com/2019/09/20/us/hezbollah-us-terror-charges/index.html (accessed June 28, 2022).
 “Summary of Terrorism Threat to the U.S. Homeland,” U.S. Department of Homeland Security, National Terrorism Advisory System Bulletin, January 4, 2020, https://www.dhs.gov/sites/default/files/ntas/alerts/20_0104_ntas_bulletin.pdf (accessed June 28, 2022).
 “(U/FOUO) Escalating Tensions Between the United States and Iran Pose Potential Threats to the Homeland,” Joint Intelligence Bulletin, January 8, 2020, p. 1, https://info.publicintelligence.net/DHS-FBI-NCTC-IranThreats-2020.pdf (accessed June 28, 2022).
 Sara Taha Moughnieh, “Sayyed Nasrallah: Suleimani Revenge Is Long Track, Trump Biggest Liar in History of US Presidency,” Al-Manar, January 12, 2020, https://english.almanar.com.lb/913904 (accessed June 28, 2022).
 Tom Winter and Pete Williams, “Feds Charge Ex-Venezuelan Politician with Recruiting Terrorists to Attack U.S. Interests,” NBC News, May 27, 2020, https://www.nbcnews.com/politics/justice-department/feds-charge-ex-venezuelan-politician-recruiting-terrorists-attack-u-s-n1215871 (accessed June 28, 2022).
 Michael Elleman, “Iran’s Missiles: Evolution and Arsenal,” United States Institute of Peace, The Iran Primer, January 15, 2021, https://iranprimer.usip.org/blog/2021/jan/15/biden-iran-missile-program (accessed June 28, 2022).
 Kenneth Katzman, “Iran’s Foreign and Defense Policies,” Congressional Research Service Report for Members and Committees of Congress No. R44017, updated January 11, 2021, pp. 10 and 12, https://fas.org/sgp/crs/mideast/R44017.pdf (accessed June 28, 2022).
 Farzin Nadimi, “The IRGC Lifts Off: Implications of Iran’s Satellite Launch,” Washington Institute for Near East Policy, Policy Note No. 84, August 2020, https://www.washingtoninstitute.org/media/377 (accessed June 28, 2022).
 Elleman, “Iran’s Missiles: Evolution and Arsenal.”
 Anthony Cordesman, with the assistance of Bryan Gold and Garrett Berntsen, The Gulf Military Balance, Volume I: The Conventional and Asymmetric Dimensions, Center for Strategic and International Studies, January 2014, pp. 14–16, https://csis-website-prod.s3.amazonaws.com/s3fs-public/legacy_files/files/publication/140131_Cordeman_GulfMilitaryBalance_VolumeI_Web.pdf (accessed June 28, 2022).
 Elias Groll, “Iran Is Deploying Drones in Iraq. Wait, What? Iran Has Drones?” Foreign Policy, June 25, 2014, https://foreignpolicy.com/2014/06/25/iran-is-deploying-drones-in-iraq-wait-what-iran-has-drones/ (accessed June 28, 2022).
 Saeed Ghasseminejad, “Iran Doubles Down on Its Military Budget,” Foundation for Defense of Democracies Policy Brief, June 3, 2016, http://www.defenddemocracy.org/media-hit/saeed-ghasseminejad-iran-doubles-down-on-its-military-budget/ (accessed June 28, 2022).
 International Institute for Strategic Studies, The Military Balance 2020: The Annual Assessment of Global Military Capabilities and Defence Economics (London: Routledge, 2020), p. 348.
 International Institute for Strategic Studies, The Military Balance 2021: The Annual Assessment of Global Military Capabilities and Defence Economics (London: Routledge, 2021), p. 337.
 Sima Shine and Zvi Magen, “President Rouhani’s Visit to Russia: A New Level of Relations?” Tel Aviv University, Institute for National Security Studies, INSS Insight No. 914, April 5, 2017, p. 1, https://www.inss.org.il/wp-content/uploads/2017/04/No.-914.pdf (accessed June 28, 2022).
 President of Russia, Events, “Meeting with President of Iran Hassan Rouhani,” June 9, 2018, http://en.kremlin.ru/events/president/news/57710 (accessed June 28, 2022).
 Reuters, “Iran Says Russia Delivers First Part of S-300 Defense System,” April 11, 2016, http://www.reuters.com/article/us-russia-iran-arms-idUSKCN0X80MM?elqTrackId=e02d5aca6d48418984d902ced0c33d77&elq=39fecef381094e0cbc6de535feb74a3c&elqaid=17334&elqat=1&elqCampaignId=10743 (accessed June 28, 2022).
 Lieutenant General Robert Ashley, U.S. Army, Director, Defense Intelligence Agency, “Worldwide Threat Assessment,” statement before the Committee on Armed Services, U.S. Senate, March 6, 2018, p. 24, https://www.armed-services.senate.gov/imo/media/doc/Ashley_03-06-18.pdf (accessed June 28, 2022).
 Farzin Nadimi, “Iran and Russia’s Growing Defense Ties,” Washington Institute for Near East Policy, PolicyWatch No. 2563, February 18, 2016, http://www.washingtoninstitute.org/policy-analysis/view/iran-and-russias-growing-defense-ties (accessed June 28, 2022).
 Defense Intelligence Agency, Iran Military Power: Ensuring Regime Survival and Securing Regional Dominance, 2019, p. 88, https://www.dia.mil/Portals/110/Images/News/Military_Powers_Publications/Iran_Military_Power_LR.pdf (accessed June 28, 2022).
 Middle East Media Research Institute, “Iranian President Raisi Visits Russia, Offers Unprecedented Strategic Partnership; Russia's Reaction Is Lukewarm,” Special Dispatch No. 9734, January 24, 2022, https://www.memri.org/reports/iranian-president-raisi-visits-russia-offers-unprecedented-strategic-partnership-russias (accessed June 28, 2022).
 Katzman, “Iran’s Foreign and Defense Policies,” p. 33.
 Zeina Karam, “Analysis: Iran Role in Syria Key Item at Trump–Putin Summit,” Associated Press, July 13, 2018, https://apnews.com/article/donald-trump-syria-ap-top-news-international-news-iran-7eebb04b92ce416495bb0ca7f0b07e54 (accessed June 28, 2022). See also Nader Uskowi, “The Evolving Iranian Strategy in Syria: A Looming Conflict with Israel,” Atlantic Council, Scowcroft Center for Strategy and Security Issue Brief, September 2018, p. 2, https://www.atlanticcouncil.org/wp-content/uploads/2019/09/The_Evolving_Iranian_Strategy_in_Syria.pdf (accessed June 28, 2022).
 BBC News, “Syrian Conflict: Russian Bombers Use Iran Base for Air Strikes,” August 16, 2016, https://www.bbc.com/news/world-middle-east-37093854 (accessed June 28, 2022).
 Oren Liebermann, Salma Abdelaziz, and James Masters, “Netanyahu Says Iran ‘Crossed a Red Line’ After Israel Pounds Iranian Targets in Syria,” CNN, updated May 11, 2018, https://www.cnn.com/2018/05/09/middleeast/israel-rockets-syria/index.html (accessed June 28, 2022).
 Carla E. Humud, Kenneth Katzman, and Jim Zanotti, “Iran and Israel: Tension over Syria,” Congressional Research Service In Focus No. IF10858, updated June 5, 2019, https://fas.org/sgp/crs/mideast/IF10858.pdf (accessed June 28, 2022).
 Anna Ahronheim and Seth J. Frantzman, “Israel Strikes Syria in Rare Daytime Attack; Syria Fires at Golan,” The Jerusalem Post, January 20, 2019, https://www.jpost.com/Breaking-News/Report-Israel-Air-Force-strikes-southern-Syria-578020 (accessed June 28, 2022).
 Tia Goldenburg, “Israeli Military Says Iran Is Slowly Pulling out of Syria,” Associated Press, May 21, 2020, https://apnews.com/d6a925c30084a34307a817de2f999bb1 (accessed June 28, 2022).
 Anna Ahronheim, “Hezbollah Training Syria’s 1st Corps to Use in Future War Against Israel,” The Jerusalem Post, May 21, 2020, https://www.jpost.com/arab-israeli-conflict/hezbollah-training-syrias-1st-corps-to-use-in-future-war-against-israel-628833 (accessed June 28, 2022).
 Yaniv Kubovich, “Iranian Redeployment in Iraq Behind Israel’s Alleged Syria Strike, Sources Say,” Haaretz, January 17, 2021, https://www.haaretz.com/middle-east-news/.premium-sources-iranian-redeployment-in-western-iraq-behind-israel-s-alleged-syria-strike-1.9449515 (accessed June 28, 2022).
 Michael Bachner, “Israel Said to Hit Iranian Sites in Iraq, Expanding Strikes on Missile Shipments,” The Times of Israel, July 30, 2019, https://www.timesofisrael.com/israel-said-to-hit-iranian-sites-in-iraq-expanding-strikes-on-missile-shipments/ (accessed June 28, 2022).
 Michael Knights, “Iran’s Cross-Border Strikes: A Pattern in Search of a Policy,” Washington Institute for Near East Policy, PolicyWatch No. 3592, March 15, 2022, https://www.washingtoninstitute.org/policy-analysis/irans-cross-border-strikes-pattern-search-policy (accessed June 28, 2022).
 Kyle Rempfer, “Iran Killed More US Troops in Iraq than Previously Known, Pentagon Says,” Military Times, April 4, 2019, https://www.militarytimes.com/news/your-military/2019/04/04/iran-killed-more-us-troops-in-iraq-than-previously-known-pentagon-says/ (accessed June 28, 2022).
 See “Mounting Missile Threat,” infra.
 Phillip Smyth, “Why Biden’s Airstrikes on Iran Militias Matter,” Washington Institute for Near East Policy, Policy Analysis, February 26, 2021, https://www.washingtoninstitute.org/policy-analysis/why-bidens-airstrikes-iran-militias-matter (accessed June 28, 2022).
 Katie Bo Williams, “US Airstrikes Follow a Spate of Sophisticated Attacks by Iranian Drones that Can Avoid US Surveillance,” CNN, updated June 28, 2021, https://www.cnn.com/2021/06/28/politics/us-airstrikes-new-iran-drone-attacks-avoid-surveillance/index.html (accessed June 28, 2022).
 Thomas Spoehr, “Failure to Respond to Iranian Al Tanf Attack Increases Risk for U.S. Forces,” Heritage Foundation Commentary, December 2, 2021, https://www.heritage.org/middle-east/commentary/failure-respond-iranian-al-tanf-attack-increases-risk-us-forces.
 General Kenneth F. McKenzie, Jr., "Posture Statement” before the Committee on Armed Services, U.S. House of Representatives, April 20, 2021, pp. 5–6, https://docs.house.gov/meetings/AS/AS00/20210420/112498/HHRG-117-AS00-Wstate-McKenzieK-20210420.pdf (accessed June 30, 2022).
 Yaya J. Fanusie and Alex Entz, “Hezbollah: Financial Assessment,” Foundation for Defense of Democracies, Center on Sanctions and Illicit Finance, Terror Finance Briefing Book, September 2017, p. 8, http://www.defenddemocracy.org/content/uploads/documents/CSIF_TFBB_Hezbollah.pdf (accessed June 28, 2022).
 U.S. Department of State, Iran Action Group, Outlaw Regime: A Chronicle of Iran’s Destructive Activities, 2020 Edition, p. 14, https://www.state.gov/wp-content/uploads/2020/09/Outlaw-Regime-2020-A-Chronicle-of-Irans-Destabilizing-Activity.pdf (accessed June 28, 2022).
 Benjamin Weinthal, “Germany Sees Increase of Hezbollah Supporters and Members—Intel,” The Jerusalem Post, June 5, 2021, https://www.jpost.com/international/germany-sees-increase-of-hezbollah-supporters-and-members-intel-670092 (accessed June 28, 2022).
 James Phillips, “Hezbollah’s Terrorist Threat to the European Union,” testimony before the Subcommittee on Europe, Committee on Foreign Affairs, U.S. House of Representatives, June 20, 2007, http://www.heritage.org/research/testimony/hezbollahs-terrorist-threat-to-the-european-union.
 Matthew Levitt, “Inside Hezbollah’s European Plots,” Washington Institute for Near East Policy, Policy Analysis, July 20, 2015, https://www.washingtoninstitute.org/policy-analysis/view/inside-hezbollahs-european-plots (accessed June 28, 2022).
 Center for Strategic and International Studies, Missile Defense Project, “Missiles of Iran,” Missile Threat, last updated August 10, 2021, https://missilethreat.csis.org/country/iran/ (accessed June 28, 2022).
 Testimony of General Kenneth McKenzie, Commander, United States Central Command, in stenographic transcript of Hearing to Receive Testimony on the Posture of United States Central Command and United States Africa Command, Committee on Armed Services, U.S. Senate, March 15, 2022, p. 35, https://www.armed-services.senate.gov/imo/media/doc/22-12_03-15-2022.pdf (accessed June 28, 2022).
 Amos Harel and Associated Press, “Iran’s Missile Attack on Syria Failed: 5 Missed, 3 Landed in Iraq,” Haaretz, June 21, 2017, https://www.haaretz.com/middle-east-news/2017-06-21/ty-article/irans-missile-attack-on-syria-failed-5-missed-3-landed-in-iraq/0000017f-ebaa-d0f7-a9ff-efefac810000 (accessed June 28, 2022).
 Humeyra Pamuk, “Exclusive: U.S. Probe of Saudi Oil Attack Shows It Came from North—Report,” Reuters, December 19, 2019, https://www.reuters.com/article/us-saudi-aramco-attacks-iran-exclusive/exclusive-u-s-probe-of-saudi-oil-attack-shows-it-came-from-north-report-idUSKBN1YN299 (accessed June 28, 2022).
 Wesley Morgan, “Joint Chiefs Chairman: Iran Intended to Kill American Troops in Missile Attacks,” Politico, January 8, 2020, https://www.politico.com/news/2020/01/08/milley-iran-american-troops-missile-096402 (accessed June 28, 2022).
 Elleman, “Iran’s Missiles: Evolution and Arsenal.”
 Zachary Keck, “Iran Has Amassed the Largest Ballistic Missile Force in the Middle East,” The National Interest, The Buzz Blog, May 22, 2019, https://nationalinterest.org/blog/buzz/iran-has-amassed-largest-ballistic-missile-force-middle-east-58882 (accessed June 28, 2022).
 Center for Strategic and International Studies, Missile Defense Project, “Shahab-3,” Missile Threat, last updated July 31, 2021, https://missilethreat.csis.org/missile/shahab-3/ (accessed June 28, 2022).
 Lieutenant General Michael T. Flynn, U.S. Army, Director, Defense Intelligence Agency, “Annual Threat Assessment,” statement before the Committee on Armed Services, U.S. Senate, February 11, 2014, p. 20, https://www.armed-services.senate.gov/imo/media/doc/Flynn_02-11-14.pdf (accessed June 28, 2022).
 Natasha Turak, “U.S. and UAE Forces Intercept Ballistic Missiles over Abu Dhabi; State Department Issues Alert,” CNBC, January 24, 2022, https://www.cnbc.com/2022/01/24/ballistic-missiles-intercepted-over-abu-dhabi-us-state-department-issues-alert.html (accessed June 28, 2022).
 Tim Hume and Alireza Hajihosseini, “Iran Fires Ballistic Missiles a Day After Test; U.S. Officials Hint at Violation,” CNN, updated March 9, 2016, http://www.cnn.com/2016/03/09/middleeast/iran-missile-test/ (accessed June 28, 2022).
 See “Iranian Threats to Israel,” infra.
 Emanuel Fabian, “IDF Drills for Multi-Front War, Including 1,500 Rockets a Day Fired from Lebanon,” The Times of Israel, May 27, 2022, https://www.timesofisrael.com/idf-drills-for-multi-front-war-including-1500-rockets-a-day-fired-from-lebanon/ (accessed June 28, 2022).
 James Phillips, “Iran’s Nuclear Program: What Is Known and Unknown,” Heritage Foundation Backgrounder No. 2393, March 26, 2010, http://www.heritage.org/research/reports/2010/03/iran-s-nuclear-program-what-is-known-and-unknown, and Nuclear Threat Initiative, “Iran: Arak Nuclear Complex,” updated/last reviewed October 25, 2021, http://www.nti.org/learn/facilities/177/ (accessed June 28, 2022).
 Valerie Lincy and Gary Milhollin, “Iran’s Nuclear Potential Before the Implementation of the Nuclear Agreement,” Wisconsin Project for Nuclear Arms Control, Iran Watch, November 18, 2015, http://www.iranwatch.org/our-publications/articles-reports/irans-nuclear-timetable (accessed June 28, 2022).
 News release, “Statement by the President on Iran,” The White House, July 14, 2015, https://www.whitehouse.gov/the-press-office/2015/07/14/statement-president-iran (accessed June 28, 2022).
 “Remarks by President Trump on the Joint Comprehensive Plan of Action,” The White House, May 8, 2018, https://uy.usembassy.gov/remarks-by-president-trump-on-the-joint-comprehensive-plan-of-action/ (accessed June 28, 2022). See also President Donald J. Trump, National Security Presidential Memorandum/NSPM-11, “SUBJECT: Ceasing United States Participation in the Joint Comprehensive Plan of Action and Taking Additional Action to Counter Iran’s Malign Influence and Deny Iran All Paths to a Nuclear Weapon,” May 8, 2018, https://fas.org/irp/offdocs/nspm/nspm-11.pdf (accessed June 28, 2022).
 James Phillips, “Sanctioning Revolutionary Guard as Terrorist Group Will Hit Iran Hard. Here’s Why,” The Daily Signal, April 8, 2019, https://www.heritage.org/middle-east/commentary/sanctioning-revolutionary-guard-terrorist-group-will-hit-iran-hard-heres-why.
 David Adesnik, “U.S. Aims Lethal Blow at Tehran’s Finances by Prohibiting Oil Exports,” Foundation for the Defense of Democracies Policy Brief, April 23, 2019, https://www.fdd.org/analysis/2019/04/23/u-s-aims-lethal-blow-at-tehrans-finances-by-prohibiting-oil-exports/ (accessed June 28, 2022).
 James Griffiths, Joshua Berlinger, and Sheena McKenzie, “Iranian Leader Announces Partial Withdrawal from Nuclear Deal,” CNN, updated May 8, 2019, https://www.cnn.com/2019/05/08/middleeast/iran-nuclear-deal-intl/index.html (accessed June 28, 2022).
 Peter Brookes, Brett D. Schaefer, and James Phillips, “Iran Nuclear Deal: Next Steps,” Heritage Foundation Issue Brief No. 5030, January 29, 2020, p. 2, https://www.heritage.org/middle-east/report/iran-nuclear-deal-next-steps.
 David Albright, Sarah Burkhard, and Andrea Stricker, “Analysis of IAEA Iran Verification and Monitoring Report,” Institute for Science and International Security Report, February 25, 2021, pp. 1 and 10, https://isis-online.org/uploads/isis-reports/documents/IAEA_Iran_Verification_Report_Analysis_for_February_2021_Final.pdf (accessed June 28, 2022).
 David Albright and Sarah Burkhard, “Iranian Breakout Timeline Now at Zero,” Institute for Science and International Security Report, June 1, 2022, https://isis-online.org/uploads/isis-reports/documents/Current_Iranian_Breakout_Estimates_June_1_2022_Final.pdf (accessed June 28, 2022).
 United States Institute of Peace, The Iran Primer, “After Long Delay, U.S.–Iran Talks in Qatar Fail,” updated June 29, 2022, https://iranprimer.usip.org/blog/2022/jun/27/europe-scrambles-revive-nuclear-talks (accessed June 30, 2022).
 Joshua Zitser, “Mossad Assassinated Iran’s Top Nuclear Scientist Using an AI-Powered, Remote-Controlled Machine Gun, Report Says,” Business Insider, September 19, 2021, https://www.businessinsider.com/mossad-remote-controlled-machine-gun-kill-iran-nuke-expert-nyt-2021-9 (accessed June 28, 2022).
 United States Institute of Peace, The Iran Primer, “Israeli Sabotage of Iran’s Nuclear Program,” April 12, 2021, https://iranprimer.usip.org/blog/2021/apr/12/israeli-sabotage-iran%E2%80%99s-nuclear-program (accessed June 28, 2022).
 Neri Zilber, “This Could Be the Next Big War That Grips the Entire World,” Washington Institute for Near East Policy, Policy Analysis, June 2, 2022, https://www.washingtoninstitute.org/policy-analysis/could-be-next-big-war-grips-entire-world (accessed June 28, 2022).
 Cordesman et al., The Gulf Military Balance, Volume I: The Conventional and Asymmetric Dimensions, p. 19.
 Kenneth Katzman, “Iran: Politics, Gulf Security, and U.S. Policy,” Congressional Research Service Report for Members and Committees of Congress No. RL32048, August 19, 2016, p. 25, http://www.parstimes.com/history/crs_august_16.pdf (accessed June 28, 2022).
 Richard Natonski and Jonathan Ruhe, “Learn from Gaza, Prepare for Hezbollah,” Breaking Defense, May 24, 2021, https://breakingdefense.com/2021/05/learn-from-gaza-prepare-for-hezbollah/ (accessed June 28, 2022).
 Avi Issacharoff, “Israel Raises Hezbollah Rocket Estimate to 150,000,” The Times of Israel, November 12, 2015, http://www.timesofisrael.com/israel-raises-hezbollah-rocket-estimate-to-150000/ (accessed June 28, 2022).
 TOI Staff, “Iran Unveils Kit to Convert Artillery Rockets into Guided Missiles,” The Times of Israel, October 7, 2019, https://www.timesofisrael.com/iran-unveils-kit-to-convert-artillery-rockets-into-guided-missiles/ (accessed June 28, 2022).
 Israel Defense Forces, “4 Reasons Why Hamas Is a Terror Organization,” June 12, 2017, https://www.idf.il/en/minisites/hamas/4-reasons-why-hamas-is-a-terror-organization/ (accessed June 28, 2022).
 Eyal Tsir Cohen, “What We Can Learn from Yet Another Round of Conflict in Gaza,” The Brookings Institution, Order from Chaos Blog, May 16, 2019, https://www.brookings.edu/blog/order-from-chaos/2019/05/16/what-we-can-learn-from-yet-another-round-of-conflict-in-gaza/ (accessed June 28, 2022).
 Grant Rumley and Neri Zilber, “A Military Assessment of the Israel–Hamas Conflict,” Washington Institute for Near East Policy, PolicyWatch No. 3489, May 25, 2021, https://www.washingtoninstitute.org/policy-analysis/military-assessment-israel-hamas-conflict (accessed June 28, 2022).
 Middle East Media Research Institute, “Former IRGC General Close to Supreme Leader Khamenei: ‘Bahrain Is a Province of Iran That Should Be Annexed to [It],’” Special Dispatch No. 6358, March 23, 2016, http://www.memri.org/report/en/0/0/0/0/0/0/9090.htm (accessed June 28, 2022).
 Maayan Groisman, “Iranian Commander Threatens to Make Bahrain’s Royal Family ‘Disappear,’” The Jerusalem Post, June 21, 2016, http://www.jpost.com/Middle-East/Iran-News/Iranian-Quds-Force-commander-threatens-to-make-Bahrains-royal-family-disappear-457354 (accessed June 28, 2022).
 Ben Hubbard, “Saudi Arabia Cuts Ties with Iran amid Fallout of Cleric’s Execution,” The New York Times, January 3, 2016, https://www.nytimes.com/2016/01/04/world/middleeast/iran-saudi-arabia-execution-sheikh-nimr.html (accessed June 11, 2021), and BBC News, “UN Condemns Attack on Saudi Embassy in Iran,” January 5, 2016, https://www.bbc.com/news/world-middle-east-35229385 (accessed June 28, 2022).
 Jon Gambrell, “Bomb-Laden Drones of Yemen Rebels Threaten Arabian Peninsula,” Associated Press, May 16, 2019, https://www.apnews.com/18f9c169f398464ba53c19e3963d3fba (accessed June 28, 2022).
 Michael Knights, “Drones over Riyadh: Unpacking the Iran Threat Network’s Tactics,” Washington Institute for Near East Policy, PolicyWatch No. 3427, January 29, 2021, https://www.washingtoninstitute.org/policy-analysis/drones-over-riyadh-unpacking-iran-threat-networks-tactics (accessed June 28, 2022).
 Seth G. Jones, Jared Thompson, Danielle Ngo, Brian McSorley, and Joseph S. Bermudez Jr., “The Iranian and Houthi War Against Saudi Arabia,” Center for Strategic and International Studies Brief, December 2021, p. 9, https://csis-website-prod.s3.amazonaws.com/s3fs-public/publication/211221_Jones_IranianHouthi_SaudiArabia.pdf?fn1d98tAhj7yOUr.IncppMueLOC4kv83 (accessed June 28, 2022).
 U.S. Department of Energy, U.S. Energy Information Administration, “Oil and Petroleum Products Explained: Where Our Oil Comes from,” last updated June 1, 2022, https://www.eia.gov/energyexplained/oil-and-petroleum-products/where-our-oil-comes-from.php (accessed June 28, 2022).
 U.S. Department of Energy, U.S. Energy Information Administration, “Today in Energy: The Strait of Hormuz Is the World’s Most Important Oil Transit Chokepoint,” June 20, 2019, https://www.eia.gov/todayinenergy/detail.php?id=39932# (accessed June 28, 2022).
 Quoted in Jacqueline K. Davis and Robert L. Pfaltzgraff Jr., Anticipating a Nuclear Iran: Challenges for U.S. Security (New York: Columbia University Press, 2014), p. 188.
 Radio Free Europe/Radio Liberty, “Iranian Commander Says Navy Could Shut down Strait of Hormuz If Needed,” updated April 28, 2019, https://www.rferl.org/a/iran-suggests-quitting-nuclear-treaty-after-u-s-tightens-sanctions/29908567.html?ltflags=mailer (accessed June 28, 2022).
 BBC News, “Tankers Almost Certainly Damaged by Iranian Naval Mines, US Says,” May 29, 2019, https://www.bbc.com/news/world-middle-east-48443454 (accessed June 28, 2022).
 Sam LaGrone, “Analyst: New Photos Are ‘Smoking Gun’ Proving Iranian Involvement in Tanker Attack,” U.S. Naval Institute News, updated June 18, 2019, https://news.usni.org/2019/06/17/analyst-new-photos-are-smoking-gun-proving-iranian-involvement-in-tanker-attack (accessed June 28, 2022).
 Radio Free Europe/Radio Liberty, “Trump Confirms He Ordered, Then Halted U.S. Military Strikes on Iran,” June 21, 2019, https://www.rferl.org/a/times-report-trump-approved-military-strikes-iran-called-off/30011802.html (accessed June 28, 2022).
 BBC News, “Iran Navy ‘Friendly Fire’ Incident Kills 19 Sailors in Gulf of Oman,” May 11, 2020, https://www.bbc.com/news/world-middle-east-52612511 (accessed June 28, 2022).
 “Israel Has Struck at Least 12 Ships Carrying Iranian Oil to Syria, Report Says,” Haaretz, March 11, 2021, https://www.haaretz.com/israel-news/2021-03-11/ty-article/israel-has-struck-at-least-12-ships-carrying-iranian-oil-to-syria-report-says/0000017f-f51d-d47e-a37f-fd3dee790000 (accessed June 28, 2022), and Amir Vahdat and Jon Gambrell, “Iran’s Largest Warship Catches Fire, Sinks in Gulf of Oman,” Los Angeles Times, June 2, 2021, https://www.latimes.com/world-nation/story/2021-06-02/iran-largest-navy-ship-catches-fire-sinks#:~:text=The%20Iranian%20naval%20support%20ship,sank%20on%20June%202%2C%202021.&text=The%20largest%20warship%20in%20the,amid%20tensions%20with%20the%20West (accessed June 28, 2022).
 Farzin Nadimi, “Iran and Israel’s Undeclared War at Sea (Part 2): The Potential for Military Escalation,” Washington Institute for Near East Policy, PolicyWatch No. 3470, April 13, 2021, https://www.washingtoninstitute.org/policy-analysis/iran-and-israels-undeclared-war-sea-part-2-potential-military-escalation (accessed June 28, 2022).
 Tom O’Connor, “Iran’s Military Fires New Cruise Missiles amid Gulf Tensions with U.S.,” Newsweek, April 26, 2017, https://www.newsweek.com/iran-military-fire-cruise-missiles-gulf-tensions-us-590462 (accessed June 28, 2022), and Editor, “Iranian Navy Test-Fires Long-Range Qadir Cruise Missile During Drills,” DefenceTalk.com, January 26, 2018, https://www.defencetalk.com/iranian-navy-test-fires-long-range-qadir-cruise-missile-during-drills-71175/ (accessed June 28, 2022).
 U.S. Department of Defense, Defense Intelligence Agency, Iran Military Power: Ensuring Regime Survival and Securing Military Dominance, pp. 32 and 55.
 Cordesman et al., The Gulf Military Balance, Volume I: The Conventional and Asymmetric Dimensions, p. 205.
 Michael Knights, Troubled Waters: Future U.S. Security Assistance in the Persian Gulf, Washington Institute for Near East Policy, 2006, p. 71, https://www.washingtoninstitute.org/policy-analysis/troubled-waters-future-us-security-assistance-persian-gulf (accessed June 28, 2022).
 Cordesman et al., The Gulf Military Balance, Volume I: The Conventional and Asymmetric Dimensions, pp. 82–95.
 Fariborz Haghshenass, “Iran’s Asymmetric Naval Warfare,” Washington Institute for Near East Policy, Policy Focus No. 87, September 2008, p. 1, https://www.washingtoninstitute.org/policy-analysis/irans-asymmetric-naval-warfare (accessed June 28, 2022).
 Sam LaGrone, “Iran Releases Maersk Tigris,” U.S. Naval Institute News, May 7, 2015, https://news.usni.org/2015/05/07/iran-releases-maersk-tigris#:~:text=The%20Iranian%20government%20released%20merchant,shipping%20company%20annouced%20on%20Thursday (accessed June 28, 2022).
 Jonathan Saul, “Tanker Attacked by Iranian Craft Collided with Iran Oil Platform in March: Owner,” Reuters, May 15, 2015, https://www.reuters.com/article/us-gulf-iran-ship/tanker-attacked-by-iranian-craft-collided-with-iran-oil-platform-in-march-owner-idUSKBN0O01F620150515 (accessed June 28, 2022).
 Reuters, “Iran Seizes Two Greek Tankers amid Row over U.S [sic] Oil Grab,” May 27, 2022, https://www.reuters.com/world/middle-east/iran-summons-swiss-envoy-over-us-seizure-iranian-oil-isna-2022-05-27/ (accessed June 28, 2022).
 James Phillips, “The Dangerous Regional Implications of the Iran Nuclear Agreement,” Heritage Foundation Backgrounder No. 3124, May 9, 2016, http://www.heritage.org/middle-east/report/the-dangerous-regional-implications-the-iran-nuclear-agreement.
 “US Accuses Iran of Conducting Rocket Test Near Warship,” Air Force Times, December 29, 2015, https://www.airforcetimes.com/news/your-military/2015/12/30/u-s-accuses-iran-of-conducting-rocket-test-near-warships/ (accessed June 28, 2022).
 See, for example, Lolita C. Baldor, “Iran Is Flying Unarmed Drones over U.S. Navy Warships in the Persian Gulf,” Chicago Tribune, August 25, 2017, https://www.chicagotribune.com/nation-world/ct-iran-drones-persian-gulf-20170825-story.html (accessed June 28, 2022), and Mark Moore, “Iran Reportedly Used Drone to Take Close-up Images of US Aircraft Carrier in Persian Gulf,” New York Post, April 22, 2021, https://nypost.com/2021/04/22/iran-flew-drone-over-us-ship-in-persian-gulf-captured-images/ (accessed June 28, 2022).
 Robert Burns, “Navy Probe: US Sailors Were Ill-Prepared for Iran Encounter,” Associated Press, https://apnews.com/article/ab692b20974a4340815eb49bb51b35e8 (accessed June 28, 2022).
 Robert Burns, “US Military Official: Iran Naval Forces Halt ‘Provocations,’” Associated Press, March 15, 2018, https://www.apnews.com/a36e23a8d549464caaea7dc1932babae (accessed June 28, 2022).
 U.S. 5th Fleet Public Affairs, “IRGCN Vessels Conduct Unsafe, Unprofessional Interaction with U.S. Naval Forces in Arabian Gulf,” U.S. Central Command, April 15, 2020, https://www.centcom.mil/MEDIA/NEWS-ARTICLES/News-Article-View/Article/2151736/irgcn-vessels-conduct-unsafe-unprofessional-interaction-with-us-naval-forces-in/ (accessed June 28, 2022).
 Sam LaGrone, “U.S. Sailors Fire Warning Shots to Ward off Harassing Iranian Fast Boats in Persian Gulf,” U.S. Naval Institute News, April 27, 2021, https://news.usni.org/2021/04/27/u-s-sailors-fire-warning-shots-to-ward-off-harassing-iranian-fast-boats-in-persian-gulf (accessed June 29, 2022).
 BBC News, “Iran Detains 10 US Sailors After Vessels Stopped in the Gulf,” January 13, 2016, https://www.bbc.com/news/world-us-canada-35295766 (accessed June 29, 2022), and France24, “Iran Seizes British Tanker in Strait of Hormuz as Tensions Mount,” modified July 20, 2019, https://www.france24.com/en/20190719-iran-seized-british-oil-tanker-strait-hormuz (accessed June 29, 2022).
 Kenneth Katzman, Neelesh Nerurkar, Ronald O’Rourke, R. Chuck Mason, and Michael Ratner, “Iran’s Threat to the Strait of Hormuz,” Congressional Research Service Report for Congress No. R42335, January 23, 2012, p. 9, https://fas.org/sgp/crs/mideast/R42335.pdf (accessed June 29, 2022).
 Sune Engel Rasmussen, “Iran’s Fast Boats and Mines Bring Guerrilla Tactics to Persian Gulf,” The Wall Street Journal, updated May 30, 2019, https://www.wsj.com/articles/irans-fast-boats-and-mines-bring-guerrilla-tactics-to-persian-gulf-11559208602 (accessed June 29, 2022). Subscription required.
 Paul Bucala, Caitlin Shayda Pendleton, Christopher Harmer, Emily Estelle, and Marie Donovan, “Iranian Involvement in Missile Attacks on the USS Mason,” American Enterprise Institute, Critical Threats Project, October 19, 2016, https://www.criticalthreats.org/analysis/iranian-involvement-in-missile-attacks-on-the-uss-mason (accessed June 29, 2022).
 Gambrell, “Bomb-Laden Drones of Yemen Rebels Threaten Arabian Peninsula.”
 United States Institute of Peace, The Iran Primer, “Timeline of Houthi Attacks on Saudi Arabia,” September 16, 2019, https://iranprimer.usip.org/blog/2019/sep/16/timeline-houthi-attacks-saudi-arabia (accessed June 29, 2022).
 BBC News, “Saudi Oil Attacks: US Says Intelligence Shows Iran Involved,” September 16, 2019, https://www.bbc.com/news/world-middle-east-49712417 (accessed June 29, 2022).
 Michael Knights, “Continued Houthi Strikes Threaten Saudi Oil and the Global Economic Recovery,” Washington Institute for Near East Policy, PolicyWatch No. 3449, March 12, 2021, https://www.washingtoninstitute.org/policy-analysis/continued-houthi-strikes-threaten-saudi-oil-and-global-economic-recovery (accessed June 28, 2022).
 Jon Gambrell, “Bomb-Laden Drone from Yemen Rebels Targets Saudi Airport,” Associated Press, May 21, 2019, https://apnews.com/d7a332d8303349b6bc2f63b8eb8675e8 (accessed June 28, 2022).
 Jon Gambrell, “US: Iran Military Could Misidentify Airliners amid Tension,” Associated Press, May 18, 2019, https://www.apnews.com/b4f5c00455fb4ffb878ed29df58abc03 (accessed June 28, 2022).
 Farnaz Fassihi, “Anatomy of a Lie: How Iran Covered up the Downing of an Airliner,” The New York Times, January 26, 2020, https://www.nytimes.com/2020/01/26/world/middleeast/iran-plane-crash-coverup.html (accessed June 11, 2021).
 Nuclear Threat Initiative, “Iran: Missile: Iran Missile Overview,” updated/last reviewed November 7, 2017, (accessed June 29, 2022).
 Seth J. Frantzman, “North Korea’s Massive New Missile Could Help Iran Threaten Israel,” The Jerusalem Post, October 11, 2020, https://www.jpost.com/international/north-koreas-massive-new-missile-could-help-iran-threaten-israel-645359 (accessed June 28, 2022).
 Lateef Mungin, “Iran Claims 2nd Launch of Monkey into Space and Back,” CNN, updated December 14, 2013, http://www.cnn.com/2013/12/14/world/meast/iran-monkey-space/ (accessed June 28, 2022).
 Nasser Karimi, “Iran Says It Sets up Space Monitoring Center,” The San Diego Union-Tribune, June 9, 2013, https://www.sandiegouniontribune.com/sdut-iran-says-it-sets-up-space-monitoring-center-2013jun09-story.html (accessed June 28, 2022).
 Reuters, “U.S. Says Iran Rocket Test Breaches U.N. Resolution,” July 27, 2017, https://www.reuters.com/article/us-iran-satellite/u-s-says-iran-rocket-test-breaches-u-n-resolution-idUSKBN1AC1YY (accessed June 28, 2022).
 U.S. Department of Defense, Defense Intelligence Agency, Iran Military Power: Ensuring Regime Survival and Securing Military Dominance, p. 37.
 Amir Vahdat and Jon Gambrell, “Iran Guard Reveals Secret Space Program in Satellite Launch,” Associated Press, April 22, 2020, https://apnews.com/0b45baa8a846f55e058e98905e290ce5 (accessed June 28, 2022).
 Agence France-Presse, “Pentagon Downplays Iranian Military Satellite as ‘a Tumbling Webcam in Space,’” The Times of Israel, April 27, 2020, https://www.timesofisrael.com/pentagon-downplays-iranian-military-satellite-as-a-tumbling-webcam-in-space/ (accessed June 30, 2022).
 J. D. Simkins, “Space Force General Trolls Iranian Military Satellite Launch—‘Space Is Hard,’” Military Times, April 28, 2020, https://www.militarytimes.com/off-duty/military-culture/2020/04/28/space-force-general-trolls-iranian-military-satellite-launch-space-is-hard/ (accessed June 28, 2022).
 Michael Rubin, “Iran’s Satellite Program Is All About Missiles,” 1945, February 8, 2021, https://www.19fortyfive.com/2021/02/irans-satellite-program-is-all-about-missiles/ (accessed June 28, 2022).
 Jon Gambrell, “Satellite Photos Show Iran Had Another Failed Space Launch,” Associated Press, March 3, 2022, https://apnews.com/article/space-launches-technology-science-business-iran-4ed71f17a612e8aef2c9b58af4538183 (accessed June 28, 2022).
 Ilan Berman, Vice President, American Foreign Policy Council, “The Iranian Cyber Threat, Revisited,” statement before the Subcommittee on Cybersecurity, Infrastructure Protection, and Security Technologies, Committee on Homeland Security, U.S. House of Representatives, March 20, 2013, p. 3, https://docs.house.gov/meetings/HM/HM08/20130320/100523/HHRG-113-HM08-Wstate-BermanI-20130320.pdf (accessed June 28, 2022).
 “Report: Iran Hackers Infiltrated Airlines, Energy, Defense Firms,” Defense News, December 2, 2014, https://www.defensenews.com/global/mideast-africa/2014/12/02/report-iran-hackers-infiltrated-airlines-energy-defense-firms/ (accessed June 28, 2022).
 Nart Villeneuve, Ned Moran, Thoufique Haq, and Mike Scott, “Operation Saffron Rose 2013,” FireEye Special Report, 2014, https://www.infopoint-security.de/medien/fireeye-operation-saffron-rose.pdf (accessed June 28, 2022).
 Ian Bremmer, “These 5 Facts Explain the State of Iran,” Time, March 27, 2015, http://time.com/3761786/5-facts-explain-iran-nuclear-talks-sanctions/ (accessed June 28, 2022). Israel’s Institute for National Security Studies similarly reported in October 2012 that “[i]n order to realize the goals of its strategy, Iran has allocated about $1 billion to develop and acquire technology and recruit and train experts.” Gabi Siboni and Sami Kronenfeld, “Iran’s Cyber Warfare,” Tel Aviv University, Institute for National Security Studies, INSS Insight No. 375, October 15, 2012, p. 2, https://www.inss.org.il/wp-content/uploads/systemfiles/375.pdf (accessed June 28, 2022).
 Frederick W. Kagan and Tommy Stiansen, The Growing Cyberthreat from Iran: The Initial Report of Project Pistachio Harvest, American Enterprise Institute Critical Threats Project and Norse Corporation, April 2015, passim, https://www.aei.org/wp-content/uploads/2015/04/Growing-Cyberthreat-From-Iran-final.pdf (accessed June 28, 2022).
 Berman, “The Iranian Cyber Threat, Revisited,” p. 3.
 Tony Capaccio, David Lerman, and Chris Strohm, “Iran Behind Cyber-Attack on Adelson’s Sands Corp., Clapper Says,” Bloomberg, February 26, 2015, http://www.bloomberg.com/news/articles/2015-02-26/iran-behind-cyber-attack-on-adelson-s-sands-corp-clapper-says (accessed June 28, 2022).
 Christopher Bronk and Eneken Tikk-Ringas, “The Cyber Attack on Saudi Aramco,” Survival: Global Politics and Strategy, Vol. 55, No. 2 (April/May 2013), pp. 81–96.
 Ben Caspit, “Israel Response to Cyber Attack Sends Clear Warning to Iran,” Al-Monitor, May 22, 2020, https://www.al-monitor.com/pulse/originals/2020/05/israel-us-iran-mike-pompeo-aviv-kochavi-cyberattack-port.html (accessed June 28, 2022).
 Joby Warrick and Ellen Nakashima, “Officials: Israel Linked to a Disruptive Cyberattack on Iranian Port Facility,” The Washington Post, May 18, 2020, https://www.washingtonpost.com/national-security/officials-israel-linked-to-a-disruptive-cyberattack-on-iranian-port-facility/2020/05/18/9d1da866-9942-11ea-89fd-28fb313d1886_story.html (accessed June 28, 2022).
 Clearsky Cyber Security, “Operation Quicksand: MuddyWater’s Offensive Attack Against Israeli Organizations,” October 2020, https://www.clearskysec.com/wp-content/uploads/2020/10/Operation-Quicksand.pdf (accessed June 28, 2022).
 Reuters, “Iranian Military Hackers Focus on U.S. Administration Officials—WSJ,” November 4, 2015, https://www.reuters.com/article/cybersecurity-usa-iran/iranian-military-hackers-focus-on-u-s-administration-officials-wsj-idUSL1N13005N20151105 (accessed June 28, 2022).
 TOI Staff, “Israel Behind Cyberattack that Caused ‘Total Disarray’ at Iran Port—Report,” The Times of Israel, May 19, 2020, https://www.timesofisrael.com/israel-said-behind-cyberattack-that-caused-total-disarray-at-iran-port-report/ (accessed June 28, 2022).
 Jack Stubbs and Christopher Bing, “Exclusive: Iran-Linked Hackers Recently Targeted Coronavirus Drugmaker Gilead—Sources,” Reuters, May 8, 2020, https://www.reuters.com/article/us-healthcare-coronavirus-gilead-iran-ex/exclusive-iran-linked-hackers-recently-targeted-coronavirus-drugmaker-gilead-sources-idUSKBN22K2EV (accessed June 28, 2022).
 Daniel Uria, “FBI Director Says Agency Thwarted Hack of Boston Children’s Hospital,” United Press International, June 1, 2022, https://www.upi.com/Top_News/US/2022/06/01/FBI-director-Christopher-Wray-agency-thwarted-hack-Boston-Childrens-hospital/6281654123694/ (accessed June 30, 2022).
 Maria Zuppello, “Iranian Cyberwar Grows Aggressive with Russia and Hizballah's Help,” Investigative Project on Terrorism, May 31, 2022, https://www.investigativeproject.org/9176/iranian-cyberwar-grows-aggressive-with-russia (accessed June 28, 2022).
 Jim Finkle, “Iranian Hackers Use Fake Facebook Accounts to Spy on U.S., Others,” Reuters, May 29, 2014, https://www.reuters.com/article/iran-hackers-idCNL1N0OE2CU20140529 (accessed June 28, 2022).
 Bill Gertz, “FBI: Iran to Launch New Cyber Attacks,” The Washington Free Beacon, May 24, 2018, http://freebeacon.com/national-security/fbi-iran-launch-new-cyber-attacks/ (accessed June 28, 2022).
 News release, “United States Seizes 27 Additional Domain Names Used by Iran’s Islamic Revolutionary Guard Corps to Further a Global, Covert Influence Campaign,” U.S. Department of Justice, November 4, 2020, https://www.justice.gov/opa/pr/united-states-seizes-27-additional-domain-names-used-iran-s-islamic-revolutionary-guard-corps (accessed June 28, 2022). See also Andrew Hanna, “The Invisible U.S.–Iran Cyber War,” United States Institute of Peace, The Iran Primer, updated November 1, 2021, https://iranprimer.usip.org/blog/2019/oct/25/invisible-us-iran-cyber-war (accessed June 28, 2022).
 National Intelligence Council, “Foreign Threats to the 2020 U.S. Federal Elections,” Intelligence Community Assessment ICA 2020-00078D, March 10, 2021, p. i, https://www.dni.gov/files/ODNI/documents/assessments/ICA-declass-16MAR21.pdf (accessed June 30, 2022).
 Ibid., pp. 5–6.
 This Index scores threat capability as it relates to the vital national interests of the United States and the role and utility of U.S. military forces. Terrorist groups clearly have the ability to conduct attacks using improvised explosive devices (IEDs), firearms, and even hijacked airplanes. The bombing of the Boston Marathon in April 2013, an attempted car bomb attack in New York City’s Times Square in May 2010, and al-Qaeda’s attacks on September 11, 2001, are stark examples. Often, the U.S. has handled terrorism as a law enforcement and intelligence collection matter, especially within the United States and when it presents a threat to particular U.S. interests in other countries. Compared to the types of threats posed by such states as China or Russia, terrorism is a lesser sort of threat to the security and viability of the U.S. as a global power. This Index does not dismiss the deaths, injuries, and damage that terrorists can inflict on Americans at home and abroad; it places the threat posed by terrorism in context with substantial threats to the U.S. homeland, the potential for major regional conflict, and the potential to deny U.S. access to the global commons. With this in mind, terrorist groups seldom have the physical ability either to accomplish their extreme stated objectives or to present a physical threat that rises to a level that threatens U.S. vital security interests. Of course, terrorist organizations can commit acts of war on a continuing basis, as reflected in their conduct in the war against al-Qaeda and its associates in which the United States has been engaged for more than two decades.