The Flow of Foreign Fighters to the Islamic State

Assessing the Challenge and the Response

Islamic State militants pass by a convoy in Tel Abyad, northeast Syria, May 2015, in an AP-verified photo from a militant website.

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Foreign fighters have long been a key element of transnational jihad. In the 1980s, foreigners flocked to South Asia to fight alongside the Afghan mujahedeen. The same thing occurred to a lesser extent in Bosnia and Chechnya in the 1990s and again following the 2003 invasion of Iraq. But the Syrian civil war and the subsequent rise of the Islamic State—also known as IS, ISIS, or ISIL—have broken new ground. Never before have jihadi foreign fighters rallied at the speed and scale as they have in the territory that IS now controls. Today, between 31,000 and 27,000 fighters from more than 86 countries are estimated to have made the journey to join the ranks of IS and other extremist groups, doubling the 2014 numbers.

These foreign fighters fill leadership roles within the organization’s hierarchy and seem to be disproportionately responsible for the atrocities and brutality for which IS has become infamous. IS uses this extreme violence to create a climate of impunity and to intimidate both civilian populations and potential enemies. In addition, the recent attacks in Paris vividly demonstrated the international terrorist threat that foreign fighters pose. Finally, these fighters present a long-term challenge to their source countries if and when they return.

In response, the U.S.-led Global Coalition to Counter ISIL has prioritized the flow of foreign fighters as one of its five major lines of effort. In 2015, United Nations Security Council Resolution 2178, or UNSCR 2178, was adopted with the specific aim of addressing the foreign fighter threat. Similarly, the coalition has established a working group to coordinate multilateral efforts to impede the flow of foreign fighters to Syria and Iraq and to implement the UNSCR. But much work remains to be done.

A key to stemming the flow of foreign fighters will be not only to treat the problem at its sources but also to prioritize within these sources. While foreign fighters come from across the globe, 12 countries have provided some 75 percent of all the fighters in Iraq and Syria. This report provides a brief snapshot of the foreign fighter threat and the government response in each of these 12 countries. Particular attention is paid to the legal framework each of these countries has established to address the foreign fighter challenge. These laws, as proscribed by the U.N. resolution, empower law enforcement and intelligence agencies as they attempt to confront the threat.

The report concludes by recommending the following five steps that the United States can take with its allies and partners to stem the flow of foreign fighters:

  1. Focus on a list of core source countries.
  2. Establish and implement a legal framework of best practices to counter the flow of foreign fighters.
  3. Prioritize measures to curb the use of Turkey as a transit hub.
  4. Improve multilateral intelligence and information sharing.
  5. Focus on gains on the battlefield against IS.

Many of the findings in this report are relevant to the developing situation in Libya, which now hosts the most significant IS presence outside Syria and Iraq. The Libyan town of Sirte, in particular, has become a top destination for foreign fighters, especially those coming from neighboring North African countries. Efforts to combat the flow of foreign fighters should be nestled within a wider strategy to combat IS in Libya and stabilize the country, which is beyond the scope of this report.

Hardin Lang is a Senior Fellow at the Center for American Progress. Muath Al Wari is a Senior Policy Analyst at the Center.