The Heritage Foundation

Backgrounder #3142 on Terrorism

August 1, 2016

August 1, 2016 | Backgrounder on Terrorism

The Threat of Islamist Terrorism in Europe and How the U.S. Should Respond

As recent events in Nice and Ansbach demonstrate, Europe faces an ongoing threat from Islamist terrorism. The United States also remains a key target for ISIS, al-Qaeda, and their supporters. The U.S. and Europe have a shared enemy and must assist each other in the defense of liberal and democratic values. For its part, the U.S. must take the fight to ISIS and al-Qaeda in the Middle East and Africa and be willing to kill or capture its enemies. The U.S. must also take a multifaceted approach to trying to halt the flow of foreign fighters. In Europe, several countries blighted by terrorism not only have devoted scant resources to tackling this problem, but also have taken an insufficiently robust line on terrorist activity. The U.S. should encourage its European allies to reverse this trend. It can also assist Europeans in breaking down intelligence firewalls that exist within individual nations while trying to improve pre-existing intelligence-sharing arrangements.

Key Points

  1. The likelihood of a terrorist attack has increased in both Europe and the United States. ISIS, al-Qaeda, and their affiliates must be militarily defeated abroad to help ease the threat at home.
  2. The threat to Europe is multifaceted: Attacks could be planned by al-Qaeda or ISIS, by cells or radicalized loners they have inspired, or by returnees trained by terrorist groups abroad. Europeans are also vulnerable to being targeted in al-Qaeda operations across the Middle East and Africa.
  3. The U.S. must step up its war against ISIS, al-Qaeda, and their affiliates by reviewing the current strategy for breaking the Islamic State’s territorial control and trying to plug its flow of foreign fighters.
  4. The U.S. should encourage European countries to take a more robust approach to counterterrorism, break down internal intelligence firewalls within individual nations, and attempt to improve pre-existing intelligence-sharing arrangements.

Europe faces a persistent threat from Islamist terrorism.[1] It is one that has increased with the rise of the Islamic State of Iraq and al-Sham (ISIS), the al-Qaeda offshoot that now controls significant parts of Iraq and Syria. The director of Europol recently described the current situation as “the highest terrorist threat we have faced for over 10 years.”[2] These security concerns are being exacerbated by unprecedented levels of migration into Europe from impoverished and/or war-torn areas of the Middle East, Africa, and the Balkans, with ISIS known to have targeted such routes for infiltration.

ISIS displayed its ability to strike at the heart of Europe during attacks in Paris in November 2015 and Brussels in January 2016, while those trained by al-Qaeda carried out the January 2015 raid on the Charlie Hebdo offices (also in Paris). The potency of these groups is enhanced by their ongoing ability to inspire small cells of radicalized supporters living in the West to carry out attacks on their behalf. The vast majority of plots in the West emanate from such supporters, who have claimed affiliation with a terrorist group without ever having traveled to popular safe havens such as Iraq, Pakistan, Somalia, Syria, or Yemen. It appears as though Mohamed Lahouaiej Bouhlel, the terrorist who killed 84 people with a 19-ton truck in Nice recently, was one such individual.

The U.S. should assist Europe by stepping up military activities against al-Qaeda, ISIS, and their affiliates. There is much it can do to ease the foreign terrorist fighter threat while also reminding the continent of its own military responsibilities. In addition, the U.S. should assist Europeans in breaking down intelligence firewalls that exist within individual nations, making better use of pre-existing intelligence-sharing arrangements and adopting a tougher approach to law and order.

ISIS: The Context

The Islamic State of Iraq, the precursor of ISIS and an al-Qaeda offshoot, was perceived by some Western policymakers as having been strategically defeated following the U.S. “surge” of 2006–2007 in Iraq, but the terrorist group had benefited from America’s effectively having withdrawn—both politically and militarily—from Iraq in the 2010–2011 period. It was also boosted by the chaos in Syria, where the Arab Spring protests were met with bloody persecution from Bashar al-Assad. In both Iraq and Syria, the Islamic State of Iraq now had significant space from which to operate.

In April 2013, Islamic State of Iraq emir Abu Bakr al-Baghdadi declared that the al-Nusra Front (ANF), the al-Qaeda affiliate operating in Syria, was essentially a front for his group. He announced the creation of a new organization: the Islamic State of Iraq and al-Sham (ISIS). This led to internal squabbling, with both al-Qaeda leaders Ayman al-Zawahiri and ANF emir Abu Mohammed al-Joulani attempting to bring al-Baghdadi to heel. Unsuccessful in doing so, ISIS was expelled from the al-Qaeda network in February 2014.

Undeterred, in June 2014, ISIS cut a swathe throughout parts of northern and western Iraq, gaining significant amounts of territory to complement the territory that it already controlled in Syria. ISIS leaders in the same month declared the return of the “caliphate,” with its capital in the northern Syrian city of Raqqa. Thousands of Europeans answered al-Baghdadi’s call to leave their homes—at times, taking entire families with them—and going to live in the newly declared Islamic state.

With ISIS gathering in strength, taking more territory and committing genocide against minority groups, the United States interven

ed. Since August 2014, the U.S. and its coalition partners (including Europeans) have carried out airstrikes against ISIS targets, stalling their advance but loosening the group’s grip on its territory only very slowly.

ISIS initially responded with a series of videos aimed at Western audiences that featured British terrorist Mohammed Emwazi beheading multiple American and British citizens in the Syrian desert. Yet the threat to life was destined to spread beyond the Middle East, and ISIS increasingly displayed a capacity to strike at targets based well beyond its “caliphate.”

ISIS and Europe

Europe’s secularism and democratic values of equality and liberty represent a direct challenge to the ISIS ideology. Therefore, the ISIS strategy focuses on carrying out attacks to present Muslims living in the West with a clear (yet false) choice: apostasy or allegiance to their “caliphate.”[3] In order to present this choice, ISIS has taken a multi-pronged approach to striking Europe.

Centrally Controlled Attacks. Carrying out attacks in Europe has been an ISIS goal for over two years.[4] A key figure in these plans has been Abdelhamid Abaaoud, a Belgian citizen of Moroccan origin who first traveled to Syria at the beginning of 2013. He was tasked by Abu Mohammed al-Adnani, ISIS spokesman and the head of ISIS’s external operations wing, with planning terrorist operations in Europe and was quickly connected to a series of plots in Belgium and France.

  • May 2014: Brussels, Belgium. Mehdi Nemmouche, a French citizen of Algerian origin, shot and killed four civilians at the Jewish Museum in Brussels. Nemmouche, an ISIS-aligned terrorist who had fought in Syria, is thought to have spoken to Abaaoud over the phone in January 2014.

  • January 2015: Verviers, Belgium. By January 2015, Abaaoud had returned to Europe from Syria and was in contact with three other recently returned ISIS terrorists based in Verviers, Belgium. According to a Belgian federal prosecutor, the Verviers cell was plotting “imminent terrorist attacks on a grand scale,” which were thwarted by Belgian authorities in January 2015 when they stormed a building occupied by the cell, killing two and arresting one. Explosives, AK-47s, walkie-talkies and police uniforms were discovered in the building.

  • April 2015: Paris, France. Algerian-born Sid Ahmed Ghlam planned what French authorities described as an “imminent” attack on churchgoers and is suspected of having murdered a gym instructor whose body was discovered on April 19, 2015. Before he could carry out his plot, Ghlam accidentally shot himself in the leg and had to call an ambulance. French authorities connected not only Abaaoud to the plot, but also another ISIS operative, Fabien Clain, a French citizen based in Syria. It is thought that Ghlam and Clain were in contact and that Ghlam had met multiple associates of Clain’s in Turkey before the planned attack.

  • August 2015: Paris, France. Four months later, in August 2015, Ayoub el-Khazzani, a Moroccan, attempted to gun down passengers in a train travelling between Amsterdam and Paris. Passengers, including two members of the U.S. Army, restrained him. El-Khazzani is believed to have been sent on this mission by Abaaoud. In the same month, French authorities arrested a French citizen, Reda Hame, on his way back from training in Syria. Abaaoud had dispatched Hame back to Europe with instructions to acquire a gun, kill civilians, and then hold hostages until he was “martyred.”

  • November 2015: Paris, France. On November 13, 2015, one of ISIS’s grandest European plans succeeded. A shocking total of 130 people were killed in Paris after a series of shootings and suicide bombings carried out by ISIS operatives in four cafes, a football stadium, and a music venue. The primarily French cell that conducted the attacks contained returnees from the Syrian–Iraqi conflict, and Abaaoud was suspected of being on the scene during the attacks on the cafes in Paris.

    In the aftermath of the Paris atrocities, Abaaoud was killed in a French police raid in St. Denis, a Paris suburb. The suspected overall commander of the cell, an Algerian called Mohammed Belkaid, was then killed in a police raid in Brussels on March 15. Belkaid had already begun to plot a set of follow-up attacks in Brussels, with two teams carrying out gun and bomb attacks. Salah Abdeslam, a member of the Paris cell who ditched his suicide vest and returned to Brussels on the night of the attack, was arrested days later.

  • March 2016: Brussels, Belgium. The ISIS threat to Europe extended beyond these individuals. On March 22, other members of the network—Ibrahim al Bakraoui, Najim Laachraoui, and Mohamed Abrini—travelled to Brussels Airport armed with Kalashnikov rifles and several bombs. They fired into the crowd at the check-in area and then detonated nail bombs that they had placed on their luggage trolleys. Just over an hour later, Khalid al-Bakraoui committed a suicide bombing in a Brussels metro station using the same type of bomb. The attacks killed 32.

The Paris and Brussels attacks were precisely what intelligence officials hoped was a thing of the past: A large cell was able to acquire guns, ammunition, and triacetone triperoxide (TATP), the explosive used in the suicide vests, all without detection. Difficulty in pulling off an attack on this scale in recent years had meant that aspiring terrorists had emphasized the use of guns and knives in simpler, cruder attacks. A plot such as the May 2013 deadly stabbing of a British soldier by violent Islamists in London was regarded as the template for the future: a very small team carrying out a crude attack using a weapon that was legal to possess and easy to acquire. The recent ISIS attacks in Europe have shown that this is not necessarily the case.

Crowdsourcing. Former New York Police Department Director of Intelligence Analysis Mitch Silber has described another ISIS tactical approach: “crowdsourced jihad.”[5] This involves “taking work traditionally performed by ‘employees’ (aka card-carrying members of ISIS) and issuing an open call for individuals outside the organization to carry it out.” This approach was encapsulated in an audio recording released in September 2014 and featuring Abu Mohammed al-Adnani, who implored supporters to launch a series of operations, regardless of their sophistication:

If you can kill a disbelieving American or European—especially the spiteful and filthy French—or an Australian, or a Canadian, or any other disbeliever from the disbelievers waging war…then rely upon Allah, and kill him in any manner or way however it may be. Do not ask for anyone’s advice and do not seek anyone’s verdict…. Smash his head with a rock, or slaughter him with a knife, or run him over with your car, or throw him down from a high place, or choke him, or poison him.[6]

The message from al-Baghdadi was clear: Supporters of ISIS should do whatever they could with whatever came to hand.

There are numerous examples of ISIS-inspired but not ISIS-controlled terrorism in the West. There were 32 ISIS plots in the West from the declaration of the “caliphate” in June 2014 through August 2015.[7] America, Canada, and Australia were targeted on multiple occasions, and 13 plots targeted seven separate European countries. These included the attacks by Omar Abdel Hamid el-Hussein, the Moroccan gunman who targeted a free speech event and a synagogue in Copenhagen, Denmark, in February 2015, killing two, and Amedy Coulibaly, the French gunman who killed five people over a two-day period in Paris January 7 and 8 and pledged loyalty to Abu Bakr al-Baghdadi in a video that was uploaded to the Internet and disseminated on Twitter after his death.


Al-Qaeda and Europe

Like ISIS, al-Qaeda wants to create a caliphate that serves as a base from which to expand and attack the West. The groups differ mainly over tactics. ISIS focuses on carrying out attacks immediately; al-Qaeda is playing a longer game. Abu Mohamed al-Joulani, the head of Syria’s al-Qaeda–affiliated al-Nusra Front, has spoken of how “[t]he instructions that we have are not to use al-Sham as a base to launch attacks on the west or Europe.” This is not due to an ideological distaste for doing so, but rather “so as not to muddy the current war” in Syria.[8] Thus, despite al-Qaeda’s not carrying out attacks with the frequency of ISIS, this does not mean that the threat has disappeared.

Open Source Jihad. Under significant pressure from U.S.-led counterterrorism operations against its senior leadership, al-Qaeda has modified its approach to targeting Europe. Complex operations such as 9/11 have become less feasible, and one branch of al-Qaeda has instead attempted to inspire supporters living in the West to act independently.

In the summer of 2010, al-Qaeda in the Arabian Peninsula (AQAP) published its first edition of Inspire, an English-language magazine. The brainchild of two American al-Qaeda members based in Yemen, Anwar al-Awlaki and Samir Khan, Inspire championed the notion of “Open-Source Jihad,” providing “[a] resource manual [that] includes bomb making techniques, security measures, guerrilla tactics, weapons training and all other jihad related activities…. [T]he open source jihad is America’s worst nightmare. It allows Muslims to train at home instead of risking a dangerous travel abroad….”[9] A recent Institute for the Study of War paper characterized Inspire as “revolutionary for the Salafi-jihadi community in that it was the first to combine the religious justifications for jihad in colloquial English with how-to manuals.”[10]

Copies of Inspire frequently turn up in terrorism investigations in the West. Particularly popular is the article on how to “Make a Bomb in the Kitchen of Your Mom,” which gives instructions on building a bomb using easy-to-acquire ingredients and material.[11] This was thought to be of use to Tamerlan and Dzokhar Tsarnaev in making the bombs they used in the Boston marathon bombing of April 2013, which killed three and injured 264.

Training and Financing. Prior to 2015, al-Qaeda’s last major successful operation in Europe was the suicide bombings on the London transport network on July 7, 2005. Yet the raid on the offices of Charlie Hebdo magazine proved that terrorists were still those operating in Europe who had been trained by the group and were determined to carry out attacks on its behalf.

Charlie Hebdo was selected for targeting by al-Qaeda’s central leadership after the magazine published a picture of the Islamic prophet Mohammed. Cherif and Said Kouachi, two French terrorists trained by AQAP in Yemen in 2011, carried out the raid. Senior AQAP figure Nasser bin ali al-Ansi claimed credit for the attack on the group’s behalf, with the group deferring to the Kouachis when it came to tactics and timing of the operation.

Attacks Abroad and Kidnap for Ransom. Al-Qaeda poses a significant regional threat, and Europeans based in al-Qaeda’s favored areas of operation have been murdered by the group in the following terrorist attacks:

  • The January 2013 In Amenas gas complex assault, carried out by a faction of Al-Qaeda in the Islamic Maghreb (AQIM);
  • The September 2013 Westgate Mall attack in Nairobi, Kenya, carried out by al-Qaeda’s Somali affiliate, al-Shabaab;
  • The November 2015 AQIM attack on the Radisson Blu hotel in Bamako, Mali; and
  • The January 2016 AQIM assault on the Splendid Hotel in Ouagadougou, Burkina Faso.

Al-Qaeda also has regularly kidnapped Europeans in order to extract ransoms from their governments. The U.S. and the United Kingdom have been highly critical of this, believing that these payments not only sustain al-Qaeda operationally, but also incentivize further kidnappings.[12]

Insufficiency of Europe’s Approach to Counterterrorism

Following the Paris attacks, Foreign Fighter Surge Teams comprised of representatives from the FBI, the Department of Homeland Security, and the Department of State were deployed to a number of European nations to provide counterterrorism assistance on border issues and intelligence sharing. This assistance has included Belgium and Greece but will also include France and Germany. This was a welcome development, as the approach of individual European countries to Islamist terrorism is failing in several key areas. The following shortcomings in Belgium, for example, were exposed by the latest ISIS attack.

Domestic Intelligence Sharing. After terrorist attacks in Europe—both those that are thwarted and those that are not—there are consistent calls from leaders and officials of the European Union (EU) for much greater intelligence sharing through a new European body designed specifically for this purpose. Belgian Prime Minister Charles Michel has even called for the creation of a “European CIA.”[13]

Yet the very nature of intelligence gathering means that countries will be reluctant to give away their secrets and how they acquired them to other countries, even allies. As Sir John Sawers, the head of Britain's MI6, has stated, “the service who first obtains the intelligence has the right to control how it is used, who else it can be shared with, and what action can be taken on it. It’s rule number one of intelligence sharing.”[14] There are sound reasons for this: If disclosures are made too readily, sources can easily be compromised and agents identified, killed, or tortured.

There also are very different privacy and surveillance expectations within Europe. The Edward Snowden disclosures were treated somewhat apathetically in the U.K., for example, compared to how they were treated in Germany. This is partially due to historical experience. In Britain, the concept of spying conjures up images of James Bond and Bletchley Park; in Berlin, it evokes recent memories of the Stasi.

There is, however, a much more immediate problem than a lack of continent-wide intelligence sharing: European countries’ domestic police, military, and intelligence agencies do not share information. As U.K. Foreign Secretary Philip Hammond recently commented:

[M]ost of our partners in Europe have an internal and an external agency and the two don’t always work closely together. Usually for historical reasons they have regarded themselves as totally different…. [T]hey just don’t have the operational integration…. [T]here are different legal structures, different powers…even turf wars.[15]

This is partially due to size and structure: France has 33 separate intelligence-collection agencies, for example,[16] and there are six separate police forces in Brussels alone.[17]

When it comes to intelligence sharing, multiple attempts have been made to help governments coordinate efforts to track foreign terrorists across international borders. Interpol’s Foreign Terrorist Fighter (FTF) program was formed in September 2014 for precisely this purpose. The Focal Point Travelers (FPT) agreement, launched by Europol in February 2015, had a similar aim: focusing on collaboration between law enforcement agencies in the U.S. and the EU.

However, a similar issue has blighted both programs. The FPT initiative also suffers from a lack of buy-in from partner nations and an incomplete database of names (approximately only 2,000).[18] More than 50 countries have contributed to the FTF database, but only around 5,000 names are on this database.[19] This is approximately one-fifth of the total of foreign terrorists thought to have travelled to Syria and Iraq.

There is also another issue with the use of Interpol: It has been unwilling to suspend the many despotic, authoritarian governments that are members of the organization and that have access to its databases.[20] The potential for abuse of the system, with such governments issuing Red Notices for political dissidents and opponents, is clear; in fact, this abuse has already taken place.[21] This makes relying on the veracity of the information in the FTF database highly problematic.

Funding. The Brussels attack demonstrated a worrying lack of capability among certain partner nations. Few European countries have advanced counterterrorism apparatuses or have devoted significant resources to defending homeland security. For example, Belgium’s domestic intelligence agency has only slightly more employees than there are Belgians who have gone to fight in the Syria–Iraq theater.[22] With the ISIS threat in Europe as advanced as it is, even countries that have not been scarred by terrorism must increase spending in this area.

Law and Order. Despite arresting Salah Abdeslam, a member of ISIS’s European network cell, Belgian authorities did not question him until the day after he was captured, and then for just two hours. This interrogation focused on the attacks in Paris and France’s application for a European arrest warrant. No questions were asked about future operations. The Brussels suicide bombings occurred shortly thereafter. It is this type of intelligence failure that led one U.S. counterterrorism official to question the competence of certain European intelligence agencies: “When we have to contact these people or send our guys over to talk to them, we’re essentially talking with people who are—I’m just going to put it bluntly—children. They are not pro-active, they don’t know what’s going on. They’re in such denial.”[23]

Belgium’s tolerant approach to law and order also contributed to the Brussels attacks. One of the bombers, Ibrahim el-Bakraoui, was released approximately six years early from a 10–year sentence for shooting a police officer with a Kalashnikov rifle during a bank robbery. Despite breaking his parole conditions that he not be allowed to travel abroad—he was picked up in Turkey in June 2015 near the border with Syria—el-Bakraoui remained free to carry out his attack in February 2016.

Ability of ISIS to Hide in Plain Sight and the Lack of Human Intelligence. In the case of both the Paris and Brussels attacks, a major terrorist cell used a European capital city as a base from which to acquire all of the materials needed to construct suicide vests and plan complicated assaults. On multiple occasions, this planning went unnoticed or unreported by the local community, suggesting distrust of the local police within this community. Furthermore, the Belgian authorities, despite being aware of the Molenbeek municipality’s reputation for radicalism, were unable to penetrate this cell with a human asset in order to gain intelligence. An improvement in either of these areas could have prevented the Brussels bombings.

Current and Future Challenges

Military Impediments. It is imperative that the ability of ISIS to govern territory be removed entirely or shrunk massively, and this can be achieved only militarily. In the short term, ISIS would seek to lash out against the West in retaliation. Therefore, security may be most imperiled in the immediate aftermath of any significant loss of territory that ISIS suffers. In the long term, however, loss of territory will puncture the image of invincibility that ISIS attempts to convey. It will help to discredit its ideology and legitimacy and subsequently will make it harder for ISIS to recruit foreign terrorist fighters.

The current U.S. military strategy against ISIS involves airstrikes and dispatching a limited number of U.S. troops to provide support to local forces attempting to retake ISIS territory. As part of this strategy, it is expected that the Iraqi army eventually will attempt to retake Mosul from the South, and Turkey will have to close the border with Syria so that ISIS has no space from which to regroup. Even if this strategy were to prove successful, however, the entire venture is complicated by the significant presence of Iranian-backed Shia militia groups that are fighting for territory of cultural and strategic influence to them and are heavily mistrusted by the Sunni population.

Several other factors are undermining the American military effort. For example, as the attacks in Brussels and Paris prove, ISIS currently poses a greater threat to European security than it poses in the U.S., yet approximately 80 percent of airstrikes against ISIS are carried out by the U.S.[24] When it comes to the military contribution against ISIS, the U.S.’s closest ally is France, which carries out approximately 12 percent of the airstrikes.[25] The U.K. also has contributed airstrikes, but the overall European effort (not to mention the meager contribution by the Gulf Cooperation Council) is clearly dwarfed by the Pentagon’s.

While the size and capacity of its military make it logical for the U.S. to assume a leading role in this war, this does not mean that European governments should shirk their responsibilities. Only five of NATO’s 28 members (the U.S., U.K., Greece, Estonia, and Poland) meet the requirement to spend at least 2 percent of their GDP on defense. Given the variety of dangers the West currently faces, this is unacceptable.

Independent Returnee Fighters. ISIS has encouraged foreigners to travel to the “caliphate” and fight alongside it in Iraq and Syria. This has increased the manpower of its army and the legitimacy of its newly formed state. While not all joined ISIS, between 5,000 and 6,000 Europeans are now thought to have traveled to Iraq or Syria.[26] It is believed that almost 2,000 have now returned to their country of origin.[27]

There is concern about the threat that these terrorist-trained individuals pose upon return. As FBI Director James Comey has commented, “Foreign fighters traveling to Syria or Iraq could, for example, gain battlefield experience and increased exposure to violent extremist elements…. [T]hey may use these skills and exposure to radical ideology to return to their countries of origin.”[28] There does not need to be operational oversight from Raqqa for returning terrorists to carry out attacks; the “caliphate” has already provided all of the ingredients they need.

So far, the returnees that have carried out attacks appear to have been a part of the Abaaoud nexus. Therefore, while the threat from returning fighters is very real, it has not yet provably manifested itself with lone, radicalized actors carrying out attacks. The presence of a surrounding network has remained important—so far.

Turkish Border Issues. The European foreign fighter pipeline to and from Syria/Iraq commonly runs through Turkey, a country that is a short, cheap flight away from Europe. The threat to Europe from ISIS-inspired terrorism cannot be eased unless the long-running issue of the porousness of the Turkish–Syrian border is resolved.

This is no easy matter; the border between Turkey and Syria is over 500 miles long. However, the U.S. government has specifically encouraged Turkey to deploy thousands of troops between the border towns of Kilis and Jarabulus, a 60-mile stretch that ISIS currently uses to shuttle foreign terrorist fighters—including the Paris attackers—in and out of the “caliphate.”

Turkey has recently made attempts to improve border security, but this was not always the case. Turkey adopted a staunchly anti-Assad approach from the early days of the Syrian civil war. This was due in part to legitimate concerns about a massacre occurring in a neighboring country (more than 250,000 have died in the Syrian civil war, with Bashar al-Assad using chemical weapons and barrel bombs and carrying out torture on an industrial scale) and in part to sectarian impulses coinciding with strategic interests in expanding the influence of Sunni governance in the Middle East.

The consequence of this approach was that Turkey opened its border to Syrian rebels following the 2011 revolution. One U.S. official commented that “[t]hey more or less let all kinds of people in—Nusra was some of them, some of them were secularists, Islamist, non-al-Qaeda groups…. They weren’t singling out any group to favor, it was more of a laissez faire approach.”[29] According to a paper published by the Foundation for the Defense of Democracies, Turkey is using these “irregular fighters” in a bid to facilitate Assad’s overthrow.[30]

This attitude allowed large numbers of Westerners to travel to Syria via Turkey and join al-Qaeda and ISIS-aligned groups. As violent Islamist groups became more prominent in the opposition, Turkey failed to toughen its border security. Turkey retains its anti-Assad position, one that has been hardened by Russia’s influence on Assad and a sharp deterioration in relations between Turkish President Recep Tayyip Erdogan and Russian President Vladimir Putin occurring following Turkey’s downing of a Russian fighter jet in November 2015.

There is now a suggestion from U.S. officials that Turkey’s attitude toward border security has changed.[31] This change, however, has surely occurred because ISIS has now carried out bombings within Turkey itself.

The Refugee Crisis. An unprecedented level of migration into Europe from the Middle East, Africa, and the Balkans is fundamentally changing the continent. Even excluding legal migration, the EU’s external border force estimated that 1 million people entered Europe illegally in 2015.[32] The true number, as the agency accepts, will clearly be larger. There are no easy answers in dealing with this problem, but security concerns must go hand in hand with humanitarian concerns, and there is no doubt that there is a severe problem when it comes to screening.

One diplomat told the House Committee on Homeland Security that refugees were barely screened at all, commenting that “there are no real controls. [The authorities] take fingerprints, accept whatever identification they provide—if they have one—and send them on their way.” The committee concluded that a “large proportion of the refugees and migrants that have entered Europe this year are unregistered, and even those who have been registered upon arrival have gone through a process that is rife with security holes.”[33 ]For example, even if registration forms, photographs, and fingerprints are taken, they are rarely cross-checked with counterterrorism watch lists.

It is hardly surprising, then, that Hans Georg-Maassen, head of the Bundesamt für Verfassungsschutz, Germany’s domestic intelligence agency, has concluded that “we have repeatedly seen that terrorists…have slipped in camouflaged or disguised as refugees”[34] and that General Philip Breedlove, NATO Supreme Allied Commander Europe, told the Senate Armed Services Committee that “the terrorists, and the returning foreign fighters are clearly a daily part of the refugee flow in Europe.”[35]

This has already shown itself to be a productive tactic for ISIS. Two Iraqi cell members who carried out suicide attacks in Paris were able to enter Greece as refugees after producing fake Syrian documentation. A Palestinian bomb maker, Ahmad al-Amin, also entered Europe with Syrian refugees in the summer of 2015.[36]

The impact of using the refugee crisis to infiltrate Europe in this manner is exacerbated by the fact that large numbers of ISIS sympathizers and other pre-existing radical networks were already operating in the continent. Some of these sympathizers have carried out attacks in Europe or have been thwarted from doing so. The presence of hardened ISIS terrorists, recruiters, and bomb makers from the Syria–Iraq conflict who are now potentially operating among, or even guiding, some of those already radicalized individuals only heightens the threat that Europe faces.

Impact on the United States

Europe and America possess a shared value system and way of life. Both (broadly) share a belief in freedom, democracy, equality, rule of law, free speech, religious freedom, judicial independence, and a respect for minority rights. They also share many of the same enemies, including ISIS and al-Qaeda. There is clearly a shared interest in not allowing mutual values to be imperiled by a mutual enemy.

The U.S. has demonstrated an enduring commitment to European security. Over 50,000 Americans were killed in World War I, and another 291,577 died during World War II. During the Cold War, the Western alliance—particularly the U.S.–U.K. Special Relationship—was fundamental in facing down the threat of Communism. It is vital that this alliance remains intact if ISIS, al-Qaeda and its supporters are to be strategically defeated. Otherwise, previous American sacrifices for Europe will have been in vain.

U.S. lives also are at risk. Americans have been killed by European ISIS terrorists. It was a radicalized British citizen, Mohammed Emwazi, who in August 2014 beheaded James Foley and Steven Sotloff, the American hostages captured in Syria. Americans were imperiled by Ayoub el-Khazzani’s planned train attack in August 2015, an American college student was killed in Paris in November 2015, four Americans were killed in the Brussels attack of March 2016, and another three were killed in the Nice attack of July 2016.

The potential for further casualties is clear. Americans make around 2.5 million trips to Britain per year. An estimated 187,000 Americans (approximately the same as the population of Salt Lake City, Utah) live in the U.K., and approximately 100,000 more live in France. American companies and military bases housed throughout Europe also are potential terrorist targets; al-Qaeda’s Nizar Trabelsi was convicted in September 2003 for planning a suicide attack against a NATO base housing U.S. soldiers in Brussels.

Without American engagement, Europe also might disengage militarily. Europe is overwhelmingly reliant on the U.S. military’s capacity to wage war, but the U.S. also requires military support from its European allies. As well as contributing to the actual fighting, European powers can provide logistical support and training assistance; European backing also adds international legitimacy to military interventions.

Yet a January 2014 article in The Guardian, based on conversations with senior officials at the Ministry of Defence (MoD), reported a “growing reluctance in an increasingly multicultural Britain to see U.K. troops deployed on the ground in future operations abroad.” This subsequently affected MoD strategic defense reviews. According to these military sources, there was “a resistance in an increasingly diverse nation to see British troops deployed in countries from which U.K. citizens, or their families, once came. There is also concern that British troops have been seen taking action mainly in Muslim societies.”[37]

This was a euphemistic way of saying that as domestic Muslim opinion disapproved of British military action abroad, deploying troops abroad—as in Iraq and Afghanistan—would no longer be possible due to the U.K.’s demographic composition.

In the U.K.’s case, although many European countries are vulnerable to similar pressures, the scale of immigration into Europe cannot be completely disassociated from national security and foreign policy strategy. This can only have been exacerbated by the refugee crisis. It is therefore vital that the U.S. remains engaged in the region to remind Europe of its international responsibilities militarily, as unpalatable as they may be to parts of the European electorate.

What Needs to Be Done

There are several actions that the United States can take to limit and ultimately to defeat the threat of Islamist terrorism, both in the U.S. and in Europe. Specifically:

  • Break the Islamic State’s control of territory. The Islamic State derives much of its legitimacy from its success. The group’s magazine, Dabiq, trumpets ISIS victories as a sign of Allah’s favor and even has a recurring feature, “In the Words of the Enemy,” which consists of quotations by senior Western officials lamenting ISIS gains. Driving ISIS from its conquered territories will undermine the group’s legitimacy and hurt its ability to recruit. American leadership is needed to achieve this. In the first instance, the U.S. should work to liberate Iraq and help it to retain territorial integrity.
  • Continue to focus on defeating both al-Qaeda and ISIS, including their regional affiliates. Military defeat of ISIS and al-Qaeda in the Middle East and Africa will enhance security in both the U.S. and Europe, and ISIS and al-Qaeda’s regional affiliates must all be considered part of the same fight. This means focusing not just on northwest Pakistan, Iraq and Syria, but also on such countries as Libya, Yemen, Afghanistan, and Somalia.
  • Be willing to capture the enemy. Intelligence is vital to the war effort. That means the U.S. must focus not solely on killing al-Qaeda and ISIS leaders, but also on capturing them. This has not been prioritized during the Obama Administration. The capture and interrogation of terrorists provides an insight into their operations that is not acquired with a drone strike.
  • Keep up the pressure on Turkey and be willing to assist in securing Turkey’s border with Iraq and Syria. This is vital to preventing the foreign terrorist flow in addition to being a key component of the current U.S. military strategy to deny ISIS territory from which to regroup.
  • Expand the Foreign Fighter Surge Teams program throughout Europe. The U.S. must also provide assistance to vulnerable European governments in identifying those who aspire to travel to Syria or Iraq and those who have returned. The Departments of Homeland Security and State are already assisting in European border security efforts, as well as encouraging greater intelligence sharing and coordination where possible. This should continue.
  • Reform Interpol to improve tracking of foreign fighters. No organization is perfectly placed to share information internationally regarding foreign fighter travel, but Interpol may be the one that is best suited to this task. These efforts must be appropriately staffed and funded and must be secure against efforts by dictatorships to exploit them.
  • Encourage European nations that are vulnerable to terrorist attack to increase spending on intelligence and adopt a more aggressive approach to counterterrorism. By carrying out two major attacks in a matter of months, ISIS has proved that the current approach to counterterrorism in Europe is insufficient. The U.S. should encourage European countries to adopt a much more aggressive stance toward this issue.
  • Reject calls for an EU-wide information-sharing network but encourage European partners to break down domestic intelligence firewalls. Instead of focusing on creating an overly ambitious new transnational EU framework, Europe should focus on encouraging achievable domestic intelligence reforms within individual European countries. The U.S. should provide assistance to its European allies on the breaking down of intelligence firewalls within countries, which would help them to streamline their operations and their dissemination of data.
  • Urge NATO members to share the military burden. Europe’s reluctance to devote sufficient resources to its military has been an area of contention for successive U.S. Administrations, but it still needs to be emphasized. While the U.S. cannot force Europeans to spend more on defense, choosing not to highlight the issue amounts to tacit approval of current spending levels.
  • Support measures to hold Bashar al-Assad accountable to the Syrian people. Assad must answer for his crimes, and the Syrian people should be given discretion as to how this process is conducted. Their options could include trial in a domestic court, inviting the International Criminal Court into Syria, or establishing a truth and reconciliation commission. Such a measure might also help to reduce the flow of foreign fighters into Syria.
  • Be cognizant of the need to defeat Islamist ideology. ISIS, al-Qaeda, and their supporters are manifestations of a broader Islamist movement. Winning the ideological battle of ideas against this movement is just as important as military victories on the battlefield.


European security—and therefore stability—remain vital to American interests. Both are currently imperiled by the sustained threat from Islamist terrorism. There is much that the U.S. could and should do to assist, as America and Europe share not just key values, but also key enemies.

Military victories against Islamist extremism abroad will lessen the danger at home. Because the acquisition of territory gives ISIS a vestige of legitimacy and a base to which recruits can travel, reclaiming this territory must therefore be prioritized. So too must addressing the foreign terrorist issue more robustly. Killing or capturing leaders of ISIS and al-Qaeda will also be an area where the U.S. can make headway in targeting those who are threatening Europe.

Outside the military sphere, assisting European nations in breaking down intelligence firewalls that exist within individual nations and attempting to improve pre-existing intelligence-sharing arrangements are worthwhile endeavors. None of the above would remove the threat to Europe—or, indeed, the U.S.—but they would certainly help to ease it.

Ultimately, however, Europe has to help itself. There is only so much that American urgings and advice can achieve. Leaders in Europe have to choose to dedicate more resources to counterterrorism and adopt a tougher approach to the dangers posed by Islamism generally. They have to be the ones, for example, who deal with ISIS by targeting refugee routes for infiltration and devising ways to counteract the radicalization of Europe’s Muslim communities.

In other words, the buck stops in Europe. At present, it is unclear whether the leaders in place are capable of meeting these significant challenges.

—Robin Simcox is Margaret Thatcher Fellow in the Margaret Thatcher Center for Freedom, of the Kathryn and Shelby Cullom Davis Institute for National Security and Foreign Policy, at The Heritage Foundation.

About the Author

Robin Simcox Margaret Thatcher Fellow
The Margaret Thatcher Center for Freedom

Show references in this report

[1] Islamism is defined as a belief that God rather than man should make law and that Islam is not only a religion, but also an all-encompassing sociopolitical system.

[2] Mark Stone, “Terror Threat to Europe ‘Highest for 10 Years,’” Sky News, March 9, 2016, (accessed April 21, 2016).

[3] Frederick W. Kagan, Kimberly Kagan, Jennifer Caffarella, Harleen Gambhir, and Katherine Zimmerman, “Al Qaeda and ISIS: Existential Threats to the U.S. and Europe,” U.S. Grand Strategy: Destroying ISIS and Al Qaeda, Report One, Institute for the Study of War, January 2016, p. 24, (accessed July 15, 2016).

[4] Ibrahim Boudina, a French citizen, fought with ISIS in Syria in late 2013 and was then dispatched back to France in January 2014 to carry out an attack in Europe. Boudina had acquired explosives in preparation for an attack before his February 2014 arrest.

[5] Mitch Silber, “Crowdsourced Jihad: The New Trend in Homegrown Terror,” The Cipher Brief, July 8, 2015, (accessed April 21, 2016).

[6] Helen Davidson, “Isis Instructs Followers to Kill Australians and Other ‘Disbelievers’,” The Guardian, September 23, 2014, (accessed April 21, 2016).

[7] Robin Simcox, “We Will Conquer Your Rome”: A Study of Islamic State Terror Plots in the West, The Henry Jackson Society, September 2015, p. 3, (accessed July 15, 2016).

[8] Agence France-Presse, “Syria Not a Launching Pad for Attacks on West Says al-Nusra Chief in TV Interview,” May 27, 2015, (accessed April 21, 2016).

[9] “Open Source Jihad,” Inspire, Issue 1 (Summer 2010), p. 32, (accessed July 15, 2016). Emphasis in original.

[10] Kagan et al., “Al Qaeda and ISIS,” p. 24.

[11] The AQ Chef, “Make a Bomb in the Kitchen of Your Mom,” Inspire, Issue 1 (Summer 2010), pp. 33–40.

[12] A British tourist kidnapped in Mali was murdered by AQIM in May 2009 when the U.K. government refused to meet the kidnapper’s demands.

[13] Robin Simcox, “Europe, Stop Trying to Make ‘Intelligence Sharing’ Happen,” Foreign Policy, April 14, 2016, (accessed April 21, 2016).

[14] Sir John Sawers, “Sir John Sawers’s Speech—Full Text,” The Guardian, October 28, 2010, (accessed April 21, 2016).

[15] Sam Jones, “UK Hits at European Anti-terror Red Tape and ‘Turf Wars’,” The Financial Times, April 6, 2016, (accessed April 21 2016).

[16] Adam Nossiter, “As Terrorists Cross Borders, Europe Sees Anew That Its Intelligence Does Not,” The New York Times, March 23, 2016, (accessed April 21, 2016).

[17] Ryan Heath, Zoya Sheftalovich, and Chris Spillane, “Belgium’s 12 Worst Terror Misses, Mistakes and Misunderstandings,” Politico.EU, March 29, 2016, (accessed April 21, 2016).

[18] Maïa de La Baume and Giulia Paravicini, “Europe’s Intelligence ‘Black Hole’,” Politico.EU, December 3, 2015, (accessed April 21, 2016).

[19] News release, “Information Sharing a Defence Against Foreign Terrorist Fighters—INTERPOL Chief,” INTERPOL, September 30, 2015, (accessed April 21, 2016).

[20] Ted R. Bromund and David B. Kopel, “Necessary Reforms Can Keep Interpol Working in the U.S. Interest,” Heritage Foundation Backgrounder No. 2861, December 11, 2013,  

[21] Ted R. Bromund, “Putin’s Long Arm: How Russia Uses Interpol to Harass Opponents,” The Weekly Standard, March 2, 2015, (accessed April 21, 2016).

[22] Loveday Morris, “Belgian Spy Chief Says He Warned on Budget Cuts as Jihadi Threat Grew,” The Washington Post, November 24, 2015, (accessed April 21, 2016).

[23] Michael Weiss, Nancy A. Youssef, and Nadette de Visser, “U.S. Officials Bash ‘Shitty’ Belgian Security Forces,” The Daily Beast, March 22, 2016, (accessed April 21, 2016).

[24] Mark Thompson, “U.S. Military Plan for Looming ISIS Offensive Takes Shape,” Time, February 26, 2015, (accessed April 21, 2016).

[25] Tom Bowman, “U.S., French, Russian Airstrikes Continue to Attack ISIS Targets in Syria,” NPR, November 18, 2015, (accessed April 21, 2016).

[26] Stone, “Terror Threat to Europe ‘Highest for 10 Years’,”; Agence France-Presse, “More than 6,000 European jihadists in Syria, EU Official Says,” April 13, 2015, (accessed April 21, 2016).

[27] Barbara Starr, “Terror Threat in Europe ‘as High as It’s Ever Been,’ Officials Say,” CNN, February 3, 2016, (accessed April 21, 2016).

[28] James B. Comey, “Statement Before the House Homeland Security Committee, Washington, D.C., September 17, 2014,” (accessed April 21, 2016).

[29] Jonathan Schanzer and Merve Tahiroglu, “Bordering on Terrorism: Turkey’s Syria Policy and the Rise of the Islamic State,” Foundation for Defense of Democracies, Center on Sanctions and Illicit Finance, November 2014, p. 10, (accessed April 21, 2016).

[30] Ibid.

[31] Adam Entous, Gordon Lubold, and Dion Nissenbaum, “U.S. Urges Turkey to Seal Border,” The Wall Street Journal, November 27, 2015, (accessed April 21, 2016).

[32] Danielle Sheridan, “Terrorists Exploiting Border Chaos to Return from Syria,” The Times, April 6, 2016, (accessed April 21, 2016).

[33] Report, Syrian Refugee Flows: Security Risks and Counterterrorism Challenges, Preliminary Findings of a House Homeland Security Review, Committee on Homeland Security, U.S. House of Representatives, November 2015, p. 7, (accessed April 21, 2016).

[34] Reuters, “German Spy Agency Says ISIS Sending Fighters Disguised as Refugees,” February 5, 2016, (accessed April 21, 2016).

[35] Associated Press, “Terrorists ‘a Daily Part’ of Refugee Flow into Europe, NATO Commander Says,” March 2, 2016, (accessed April 21, 2016).

[36] Alfred de Montesquiou, “Pr Pierre Mols : ‘Nous avons soigné Abdeslam comme n’importe quel patient,’” Paris Match, March 31, 2016, (accessed July 19, 2016).

[37] Patrick Wintour, “Multicultural Britain Rejecting Foreign Conflict, MoD Admits,” The Guardian, January 22, 2014, (accessed April 21, 2016).