The Foreign Fighter Threat from ISIS and the Syrian Conflict

One of the defining features of the rise of ISIS is its foreign fighter dimension.  While foreign fighters have been a staple of the evolution of the global jihadist movement since the Soviet invasion of Afghanistan in the 1980s, the scale, cause, and context of the foreign fighter phenomenon since the beginning of the Syrian crisis has caused unique concern, particularly in the United States and Europe.  According to a 2015 study conducted by the Soufan Group, between 27,000 and 31,000 individuals from over 86 countries have traveled to Syria and Iraq since the Syrian conflict began in 2011—roughly the same number of jihadist foreign fighters who joined armed conflicts around the world since 1980.  Moreover, from 2014, when ISIS declared its caliphate, to 2015, the total figure doubled, with 5,000 of those individuals from Western Europe (twice the number of Europeans from 2014), and nearly 300 from the United States.  While most of the fighters hail from other parts of the Middle East (with Tunisia boasting the highest numbers), the foreign fighter phenomenon presents an added security concern because of the concurrent Syrian migrant crisis, free movement in the Eurozone, the possibility that some fighters also hold European passports, and the particularly lethal training and indoctrination they receive in Syria and Iraq.  This backgrounder offers an overview of the foreign fighter phenomenon since the beginning of the Syrian conflict in 2011, an assessment of the threat foreign fighters pose upon their return home, and recommendations to U.S. policymakers on how best to address it.

  • Unique Appeal of ISIS to Foreign Fighters. While armed conflicts abroad have consistently been a feature of jihadism, especially where there is the perception of a non-Muslim power oppressing Muslims, a number of features of both the Syrian conflict and the rise of ISIS are unique.  The first is the resonance of the sectarian dimension in the Syrian conflict, where Bashar al-Assad, as well as Shiite militias with the backing of Iran, are depicted as killing innocent Muslims.  The setting of Syria is doubly important as it is the site of the apocalypse foretold in early Islamic sources—a theme that groups like ISIS exploit for their cause.  ISIS’s state-building project offers not only the potential of battlefield heroism in the name of this apocalyptic battle, but also an Islamic utopia, which attracts a much broader demographic of disaffected youths in Western societies. Finally, analysts have pointed to Syria’s proximity and ease-of-access, as compared to places like Afghanistan or Bosnia.
  • From Foreign Fighters to Domestic Terrorists. Despite periodic incidents of both foiled and successful terrorist plots in the United States and Europe linked to ISIS or al-Qaeda (whether directed or inspired), to date there is no agreement about the scale or likelihood of the threat posed to Western targets by returning foreign fighters.  Those who believe the threat to the homeland is overstated cite the fact that those joining the cause of ISIS are uniquely drawn to fighting a sectarian apocalyptic battle against Shiites in Syria and Iraq rather than fighting the West.  They claim the foreign fighters are often either battle-weary or disillusioned after returning from the region, and that their training in Iraq and Syria prepares them for short-range counter-insurgency operations rather than coordinating large scale attacks in civilian centers.  Others, however, cite AQ’s experience with foreign fighters in which jihadists typically continued carrying on their fighting in their home countries, particularly in the Middle East.  Where the two views agree is that foreign fighters will take advantage of weak states to continue their fighting (which may apply more to countries outside the U.S. and Europe), and that they could play ancillary roles—recruiting others and providing networks and information about where and how to travel.  The latter two points underscore the fact that foreign fighters will remain a serious national security concern even if they themselves do not pose terrorist threats.

Recommendations for U.S. Policymakers

While it is difficult to anticipate with precision how the foreign fighter phenomenon will evolve, the U.S. government could take a number of steps to both manage and monitor the flow of potential fighters to Iraq, Syria, and other hot spots, as well as tailor its law enforcement and intelligence policies to the real threat posed to the homeland:

  • Enhance U.S. Border Control Policy and Coordinate with those of European and Regional Partners. A major conduit for the foreign fighter flow in and out of Europe is the Schengen agreement as well as lax border control in Turkey and elsewhere in the Middle East.  While European states have become concerned about its border policies in recent months with the migrant crisis, their policy conversations have been driven principally by domestic politics and are not sufficiently coordinated across European member states and Middle East partners, in particular Turkey.  The U.S. could help international policy on this subject by highlighting the distinct threat posed by foreign fighters embedding themselves amid migrants and developing deeper roots and networks in their home countries.
  • Closer Coordination with European Intelligence and Law Enforcement. Beside different border policies and frameworks, the terrorist attacks in Europe over the last several months highlighted major disparities in the states of American and European counter-terrorism infrastructure.  Moreover, European standards on what constitutes support for terrorism varies markedly from both the U.S. and among European member states.  Aligning and enforcing our definition of support for terrorism and coordinating our intelligence more closely will ensure not only more precision about the composition of terrorist networks, but also more systematic approaches to targeting terrorist activities (financing, material and rhetorical support, fighting).
  • Partnerships with Muslim Communities and Exploiting Returned Fighters. Stronger partnerships between law enforcement and local Muslim communities in both the United States and Europe could not only provide early warning and intelligence into potential targets, but could also lead to greater trust between the two, especially in Western countries host to insular and unassimilated communities. Moreover, counter-ISIS efforts by U.S. and European governments could exploit those returning fighters disillusioned by their experiences in Iraq and Syria for both intelligence and counter-messaging purposes.