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As I wrote in my book “Road Warriors” and in a recent spinoff article in Political Science Quarterly, jihadists who travel abroad to fight and train—foreign fighters—can become highly lethal terrorists. This danger has received renewed attention in recent months with the withdrawal of U.S. forces from Afghanistan and the Taliban takeover there. These events have kindled fears that, as was true in the 1990s, the country may become a base for international terrorist groups like al-Qaeda and a home for foreign fighters to train and plot. Such concerns, however, neglect the tremendous progress the United States and its allies have made in the post-9/11 era in combating the foreign fighter scourge and limiting the danger they pose to the United States, Canada and Europe.
Still, foreign fighters remain a powerful jihadist force worth understanding. Foreign fighters orchestrated and conducted many of the most important jihadist attacks in the past 25 years. Foreign fighters helped plot and organize the 1998 al-Qaeda attacks on two U.S. embassies in Africa that killed 224 people, al-Qaeda bombings of transportation targets in Spain in 2004 that left 191 people dead and in London in 2005 where 52 innocents died, the bombings and shootings in Paris by the Islamic State in 2015 that killed 130 people, and, of course, the 9/11 attacks, in which almost 3,000 people perished.
As horrific as this list is, foreign fighters often play even more lethal roles outside of their involvement in terror attacks. Their stature and zealotry enables them to better incubate new insurgent groups and radicalize existing ones. This, in turn, worsens existing civil wars and makes them more likely to spread to neighboring countries. These conflicts plague many Muslim-majority countries, with hundreds of thousands dead in Syria, Yemen and other states where jihadist groups have a significant presence.
After militants return from time abroad, they are often far more dangerous. Research by the scholar Thomas Hegghammer found that plots involving foreign fighters are more likely to succeed than those without foreign fighters—and are more lethal when they do succeed. Often, the fighters receive specific training on how to build a bomb, hide from an intelligence service or otherwise successfully plot a terrorist attack. Even when this training is lacking, time in a war zone often makes these fighters more dedicated and steady while plotting an attack. Terrorist groups like al-Qaeda and the Islamic State try to indoctrinate recruits, taking individuals with specific grievances such as the Syrian civil war and introducing them to a more global, and more anti-Western, agenda. Finally, individuals return and are more networked, better able to work with like-minded individuals, some of whom are still overseas, to conduct attacks.
The post-9/11 era overall saw a decline in the role of foreign fighters with regard to successful terrorist attacks. In the United States, the foreign fighter role has been negligible. In the successful post-9/11 jihadist attacks on the U.S. homeland, attackers were inspired by al-Qaeda and Islamic State propaganda and otherwise acted without having spent time overseas in a training camp or fighting in a foreign war. In Europe, the picture is more mixed, with the 2015 Paris attacks being but the bloodiest example of how foreign fighters remain a threat. In recent years, however, more Islamic State-linked attacks have been carried out by local supporters than by foreign fighters. Throughout Europe, “homegrown violent extremists” have far outpaced foreign fighter returnees in terms of terrorist activities.
No single policy explains why foreign fighters have become less of a threat to the West. Rather, the “Swiss cheese” model now familiar to many people because of efforts to combat the coronavirus can be applied to counterterrorism: Different policies at different stages provide limited protection in isolation, but the combined effort is highly effective.
Let’s start with jihadist activity even before travel overseas occurs. Before 9/11, individuals in the West could often plot, recruit, and fundraise with little interference; in the United States, bureaucratic rivalries and inattention hindered effective collection on jihadists, while many European states were highly tolerant of travel to overseas war zones. Today, governments carefully monitor suspected jihadist activity on their soil, trying to disrupt potential cells before they occur. In the United States and many other countries, going abroad to help a jihadist group in a war is a crime, and volunteers are regularly jailed for attempting to do so.
If individuals escape initial scrutiny and try to travel, they are far more likely to be apprehended at the airport or in transit. Before 9/11, no U.S. government agency systematically analyzed terrorist travel, “thus missing critical opportunities to disrupt their plans,” in the words of the 9/11 Commission staff. This changed dramatically after 9/11, with far more resources and focus on the travel challenge. Many European states moved more slowly, but as thousands of Europeans traveled to Syria to fight, they began to devote more effort to stopping travel.
In the past, foreign fighter destinations like the Taliban’s Afghanistan were intelligence black holes. Now the United States and other governments monitor war zones and suspected havens: The intelligence is far from perfect, but it’s leagues ahead of where it was on 9/11. With drones and raids by special operations forces, the United States also tries to kill jihadist leaders in war zones. Even when it fails to do so, the constant risk forces groups to limit open training and otherwise keep their heads down, making the haven far less safe. When leaders communicate from the war zone, they may be targeted or reveal the identity and location of the local operatives they are trying to support: Such links become a vulnerability.
The return home is also risky. Traveling from a war zone is a red flag for border officials. Individuals who fool or elude border security are still not safe. The domestic intelligence services that once were ignorant of whether people traveled to and from places like Afghanistan are now on high alert, working with community officials to identify dangerous elements.
Such efforts, of course, are uneven and are no guarantee of complete success. Not all states have devoted sufficient resources to the problem, and many Muslim-majority countries have limited capacity to monitor returned foreign fighters and otherwise disrupt the threat. Some suffer brutal civil wars or localized instability, which offers returnees opportunities for further fighting and networking. Many European states, for their part, have refused to allow their nationals to return to face justice, fearing that their judicial systems are inadequate or that the government would be seen as “soft” on terrorists.
In North America and Europe, however, the biggest problem today with regard to jihadist terrorism is inspired terrorism, with supporters often learning about it via social media, rather than foreign fighters. Because groups are aware of the risks facing would-be volunteers, they encourage them to act locally. Moreover, jihadist wins like Afghanistan will provide hope to their supporters. Inspirational terrorism is usually less lethal than terrorism linked to foreign fighters, but it will prove far harder to stop.
Fighting this danger involves an overlapping, but at times different, counterterrorism tool set. As with foreign fighters, good relations with Muslim communities are vital, as they are more likely to know any dangerous elements in their midst. Successfully combating inspired terrorism requires working more effectively with social media companies, and there has been progress on this front. Far more difficult is discrediting the overall jihadist narrative that proclaims the West as an enemy and the United States as a cruel oppressor of Muslims—a narrative that, despite years of U.S. efforts, remains robust.