Twenty Years After 9/11: Never Forget

Report Defense

Twenty Years After 9/11: Never Forget

September 9, 2021 12 min read Download Report

Authors: Steven Groves, Daniel Kochis, Joshua Meservey, Lora Ries, Nicole Robinson and Jeff Smith


Twenty years after the horrific attacks on the U.S. homeland, the world is as dangerous as or even more dangerous than it was on the morning of September 11, 2001. The U.S. faces not just major threats in China and Russia, but the increased threat of transnational terrorism. Those who are in charge of the levers of U.S. national security—President Biden first and foremost among them—must be up to the task of constant vigilance.

Key Takeaways

9/11 warns us that lands over which we have little or no intelligence visibility create an environment for terrorist organizations that desire to strike America.

Twenty years later, the world is just as dangerous, and the U.S. faces an increased threat of transnational terrorism.

Those in charge of the levers of U.S. national security—President Biden first and foremost among them—must be up to the task of constant vigilance.

This Saturday, for the 20th year, the United States and other nations will observe the anniversary of the horrific terrorist attacks of September 11, 2001. These annual commemorations have always been momentous and solemn occasions, and as always, the attention of the American people should be on the men, women, and children who needlessly died that day. It is right and proper that our focus should be on the tragic loss of those lives.

At the same time, however, most Americans must reflect on the lessons of 9/11 and how it came to pass that more than 2,600 Americans were killed over the course of a few hours that day. The central questions on the minds of the American people are whether the United States has learned the lessons of 9/11 and whether the government has lived up to the commitment that encapsulates the post-9/11 admonition of the American people: – Never forget.

The central lesson of 9/11 is that loosely governed lands over which the U.S. has little or no intelligence visibility create the permissive environment that is most attractive to terrorist organizations that desire to strike America. The collapse of Afghanistan into the arms of the Taliban has once again set the stage for that nation to host terrorist groups that target the West. Already there are reports that the Taliban’s return has inspired and boosted the morale of militants in Southeast Asia, some of whom plan to travel to Afghanistan for training.REF Al-Qaeda will certainly seek to reconstitute itself and, harbored by the Taliban, may once again become a threat to America and its allies. The Islamic State and other terrorist groups may also seek sanctuary in Afghanistan.

The Biden Administration has given assurances that the U.S. withdrawal from Afghanistan will not result in a repeat of the past. U.S. Secretary of State Antony Blinken has stated that the Taliban “has made a commitment to prevent terrorist groups from using Afghanistan as a base for external operations that could threaten the United States or our allies, including al-Qaida and the Taliban’s sworn enemy, ISIS-K.” Blinken also said that the U.S. will “remain vigilant in monitoring threats ourselves” and will “maintain robust counterterrorism capabilities in the region to neutralize those threats.” But are vigilance and supposed regional capabilities sufficient to protect the homeland in the absence of a U.S. embassy, a CIA base of operations, and diminished surveillance capacity in the mountains and valleys of Afghanistan?

The Worldwide Threat

Moreover, at present, threats to the U.S. homeland may come not just from Afghanistan, but from any corner of the globe.

Europe. In Europe, the chief threat to U.S. citizensREF from Islamist terrorism are attacks against the myriad historic, cultural, and transit node soft targets. Terrorist attacks against U.S. installations in Europe also remain a threat. In 2020, for example, five Tajik nationals acting on behalf of ISIS came to Germany seeking refugee status and were arrested for plotting terrorist attacks against U.S. Air Force bases and personnel.REF

Western Europe remains a major recruiting ground for Islamist terrorism. In France alone, the nation’s terrorism watch list contains over 8,000 people.REF Large-scale migration to Europe since 2015 has strained intelligence and counterterrorism resources, reemphasized the failure of many European nations to assimilate new arrivals, and energized new attempts to address shortfalls.REF

The robust sharing of intelligence and inclusion of nearly all European nations in the Visa Waiver Program greatly reduce the risk of Islamists from Europe entering the U.S. However, the threat to American citizens on European soil remains stable and consistent.REF

Middle East. The threat of terrorism in the Middle East has not ended. The U.S. faces new and existing threats from radical Islamist groups that emerged from the power vacuum created by the 2011 civil war in Syria and Yemen. Of these groups, the so-called Islamic State in Syria, Iraq, and Yemen and Al-Qaeda in the Arabian Peninsula capitalized on regional instability to recruit fighters from the United States. Many of these radicalized individuals have gone on to conduct homegrown terrorist attacks on U.S. soil. Iran’s backing of sub-state entities like Hamas (the Palestinian territories); Hezbollah (Lebanon); the Mahdi movement (Iraq); and the Houthi insurgents (Yemen) has also created a destabilizing environment that fuels terrorist activity in the region.

South Asia. South Asia is host to a wide variety of Islamist terrorist groups. A number of groups with limited influence and ambitions operate in the Maldives, Bangladesh, and India. However, most of the region’s deadliest terrorist groups are headquartered in and supported by Pakistan. Pakistan’s Inter-Services Intelligence (ISI) has long sponsored terrorism as an extension of its foreign policy, particularly in Afghanistan and the disputed Kashmir region.

Pakistan’s support for the Taliban after its eviction from Afghanistan in 2001 was instrumental in the group’s return to power two decades later. The threat to the U.S. from Islamist terrorism in South Asia has grown considerably since the Taliban returned to power. Of particular concern is the elevation of several members of the Haqqani Network to senior government positions. The Haqqani Network is responsible for some of the deadliest attacks on U.S. forces in Afghanistan and is known to have close links to the ISI and al-Qaeda.

Africa. The Islamist terrorism problem in Africa is on a negative trajectory. Africa hosts more than 20 such groups, nearly all of which are either ISIS or al-Qaeda affiliates.REF Some have receded but remain potent, while others have gained, especially in the Sahel where violent terrorist events have exploded sixteenfold since 2016.REF The twin pillars of the problem, the Salafi-jihadi ideology and government failure that facilitates it, are not abating, so neither will the terrorist threat.REF The danger to the U.S. stems primarily from the possibility that these groups will opportunistically attack local American interests and from their ability to harm American allies and destabilize fragile regions. The longer-term danger stems from these groups enjoying a haven that will allow them to build the capabilities for attacking the U.S. homeland.

The Homeland. The U.S. risks Islamist terrorist threats in the homeland from homegrown terrorists on multiple fronts. With an open southern border, the Biden Administration is permitting historic numbers of aliens to enter and remain in the U.S. illegally.REF Unprecedented numbers of known and suspected terrorists have been crossing the border since President Biden has been in the White House, according to the recently removed Chief of the U.S. Border Patrol.REF Surely, the revitalized Islamist terrorist groups are eying our southern border as a gateway they can exploit to place their fighters in the U.S.

Another unfortunate pattern of homegrown Islamist terrorism has been lawful immigration and the second generation of migrants becoming disillusioned and radicalized due to inadequate assimilation. Terrorists are known to exploit the refugee process—both here and abroad—to gain a foothold in a target country.REF Other lawful immigration programs such as our Diversity Visa Program have provided pathways for radicalized terrorists.REF

A third front does not require immigration, but rather a simple Internet connection. Now, with unencumbered operations, time, and power, the Taliban, ISIS-K, al-Qaeda, and other terrorist groups can devote more time and effort to using the web to spread their radical ideology to those who are already in the U.S.

What Needs to Be Done

The United States has had 20 years to learn from the tragedy of 9/11 and strengthen U.S. defenses against another major terrorist attack. The U.S. will need to remain vigilant and aggressive to counter such attacks. In the years ahead, the Biden Administration should take the following steps to protect the homeland.

  1. Secure U.S. borders and fully enforce immigration law. To prevent terrorist attacks, it is paramount that the Biden Administration reverse its border and immigration policies. This includes fulling implementing the Migrant Protection Protocols (“Remain in Mexico” program), as now ordered by the U.S. District Court for the Northern District of Texas; ending “catch and release”; fully using Title 42 authority to turn back migrants for reasons of public health safety during the COVID pandemic; completing construction of the planned border wall system; ending pursuit of amnesty for millions of illegal aliens; and detaining and removing aliens consistent with immigration law.
  2. Depoliticize the Departments of Homeland Security and Justice. These departments need to prioritize the most dangerous threats to Americans correctly. Radical Islamic terrorism is the number one threat to our country—not white supremacists, those protesting COVID mandates, or climate change. If the Administration wants to continue to prevent terrorist attacks in the U.S., DHS and DOJ must work together to root out immigration fraud and exploitation as well as on-line radicalization.
  3. Assimilate newly and recently naturalized citizens and other appropriate migrant populations. Assimilation is a necessary component of successful U.S. resettlement and homeland security. Assimilation into American society, using a common language, and understanding American civics are key to immigrants’ success. Embracing the American creed, learning English, and gaining an education help immigrants to build an American identity and gain the knowledge, skill sets, and social capital that increase their sense of belonging in American society. Assimilation does not require that refugees forget their history, culture, or language. Patriotic assimilation simply asks that immigrants to the U.S. embrace the principles of the United States and develop loyalty to the U.S. and fellow Americans above other countries and peoples. The growing number of Islamist terrorist attacks in Europe, as well as terrorism-related and violent crimes in the U.S., by radicalized refugees are a reminder that non-assimilation is a direct threat to homeland security and societal cohesion.
  4. Continuously vet at-risk immigrant populations. The current rushed Afghan evacuation and ongoing vetting concerns generate a lack of confidence in thorough vetting, particularly when the U.S. no longer has staff or military in Afghanistan to verify identities and other relevant information. The U.S. government should continuously vet at-risk populations for a reasonable period of time to gain confidence in the bona fides of such individuals and prevent radicalization.
  5. Prioritize online screening for terrorist activity and radicalization. The private sector also has responsibilities. Social media and other Internet service providers should stop censoring, labeling, and deplatforming users for COVID and election “misinformation.” Instead, such companies should prioritize searching for and removing terrorists and terrorist content from their platforms.
  6. Hold Pakistan accountable. On New Year’s Day 2018, the Trump Administration took the dramatic step of suspending billions in U.S. aid to Pakistan. President Trump was right to hold Pakistan to account for its decades-long sponsorship of terrorist groups and to dismiss warnings that a cessation of aid would carry disastrous results. The suspension of aid was a welcome first step, but it is not nearly enough. Pakistan was instrumental in supporting the Taliban and Haqqani Network and their takeover of Afghanistan in 2021. In order for Pakistan and the U.S. to resume a productive partnership, Pakistan must take verifiable steps to break decisively with violent Islamist groups such as the Taliban, the Haqqani Network, and Lashkar e Taiba. Until then, the U.S. should be prepared to impose sanctions and severe costs on the Pakistani state, military, and intelligence services.
  7. Pressure countries that export extremist ideologies. Gulf Arab states especially have spent billions of dollars exporting Salafism, a fundamentalist practice of Islam, for decades. Virtually all Islamist terrorist groups subscribe to a sub-sect of Salafism, known as Salafi-jihadism, and Salafism’s spread broadens the pool of Muslims who share core theological beliefs with the terrorists. The U.S. should urge Salafi-exporting countries to stop the practice and use their resources to support the tolerant and peaceful sects of Islam.
  8. Strengthen counterterrorism cooperation with India. America's growing ties with India constitute one of its most promising new strategic partnerships. The two democracies have suffered from major high-profile terrorist attacks and are prime targets for Islamist terrorist groups. India–U.S. counterterrorism and intelligence-sharing cooperation has grown considerably since the turn of the century and should be strengthened further. India and the U.S. also share similar concerns and objectives in Afghanistan and should cooperate to mitigate the threat from terrorism emanating from the “Af-Pak” region, particularly after the August 2021 takeover of Afghanistan by the Taliban and Haqqani Network.
  9. Remain actively engaged in the Middle East. Although individuals in Washington have advocated for the U.S. withdrawal of forces from the Middle East, disengagement is not a viable option. Instead, the U.S. should work closely with partner countries in the region to bolster security and military capabilities and improve intelligence sharing and cooperation to deter external threats, advance counterterrorism operations, and promote regional stability.


Twenty years after the horrific attacks on the U.S. homeland, the world is as dangerous as or more dangerous than it was on the morning of September 11, 2001. The U.S. faces not just major threats in China and Russia, but the increased threat of transnational terrorism. Those who are in charge of the levers of U.S. national security—President Biden first and foremost among them—must be up to the task of constant vigilance.

Steven Groves is the 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. Daniel Kochis is Senior Policy Analyst in European Affairs in the Thatcher Center. Joshua Meservey is Senior Policy Analyst for Africa and the Middle East in the Douglas and Sarah Allison Center for Foreign Policy, of the Davis Institute. Lora Ries is Director of the Center for Technology Policy, of the Davis Institute, and Senior Fellow for Homeland Security. Nicole Robinson is Research Associate for the Middle East in the Allison Center. Jeff Smith is Research Fellow for South Asia in the Asian Studies Center, of the Davis Institute.


Steven Groves
Steven Groves

Margaret Thatcher Fellow

Daniel Kochis
Daniel Kochis

Research Fellow, Margaret Thatcher Center for Freedom

Joshua Meservey
Joshua Meservey

Former Research Fellow, Africa

Lora Ries
Lora Ries

Director, Border Security and Immigration Center

Nicole Robinson
Nicole Robinson

Senior Research Associate, Middle East

Jeff Smith
Jeff Smith

Director, Asian Studies Center