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Jihadi foreign fighters: How dangerous?

- May 31, 2013

In our continuing collaboration with political science journals, the following guest post is written by Thomas Hegghammer (@hegghammer), a political scientist and historian at the Norwegian Defence Research Establishment (FFI). He is currently the Zuckerman fellow at Stanford’s Center for International Security and Cooperation (@CISAC).  His article in the February 2013 issue of the American Political Science Review to which the post refers is available ungated here through June 15, 2013.


Last week, radical Islamists stabbed a British soldier to death in Woolwich, South London. Meanwhile other Western jihadists were busy fighting Bashar al-Assad’s army in Syria. Although these activities seem unrelated, they raise an interesting question: Why do some Western jihadists attack at home while others fight abroad? Moreover, if jihadists are so keen to attack the West, why do some of them leave, given that they are already “behind enemy lines”? And how worried should we be about the prospect of foreign fighters returning to perpetrate terrorist attacks?

My article in the February 2013 issue of the American Political Science Review tries to answer these questions by looking at where Western jihadists have chosen to fight over the years and why. I rely on open-source data, including a new dataset on jihadi plots in the West (1990-2010) and a set of numerical observations of foreign fighter flows. My five main findings are as follows:

  1. Foreign fighting is by far the most common activity. Foreign fighters outnumber domestic attackers by at least 3 to 1 (over 900 vs. 300 individuals over 20 years).
  2. Western jihadists seem to prefer foreign fighting for normative reasons. They heed religious authorities who consider fighting in warzones more legitimate than killing civilians in Western cities.
  3. Most foreign fighters appear not to leave with the intention to train for a domestic operation.  However, a minority do acquire this motivation after their departure.
  4. Most foreign fighters never return for domestic plots. In my data, at most 1 in 9 foreign fighters came home to roost.
  5. Those foreign fighters who do return are significantly more effective operatives than non-veterans. They act as entrepreneurs and concoct plots that are twice as likely to kill.

For policymakers, the main takeaway from the article is that foreign fighters as a group pose somewhat less of a terrorist threat to the West than is often assumed. The widespread view of foreign fighters as very dangerous stems from their documented role in several serious terrorist plots in the past decade. However, this reasoning selects on the dependent variable, because it considers only the small subset of foreign fighters who returned to attack, disregarding the majority who were never heard from again. A related, but equally flawed assumption is that all foreign fighters leave for training, as part of a cunning strategy to “come back and hit us harder”. The fact that some foreign fighters trained and returned does not mean that all foreign fighters departed with that intention. As it turns out, not even those who did train and return say they planned it from the start. It follows from this that a government approach which treats all foreign fighters as domestic-terrorists-in-the-making risks wasting resources, because so few foreign fighters, statistically speaking, will go on to attack in the West.

A first step toward a more efficient counterterrorism strategy is to differentiate between outgoing and homecoming foreign fighters and focus resources on the latter. Some countries might consider going a little lighter on outgoing foreign fighters. The US government today spends considerable resources investigating, prosecuting, and incarcerating Muslims who merely attempt to join conflict zones like Somalia. While there should clearly be sanctions in place to deter foreign fighting, the deterrence effort could be better calibrated to the documented threat. By contrast, Islamists returning from conflict zones or neighbouring countries should be watched very carefully. This is hardly news to Western intelligence services, but the fact that the last two major attacks in the West, the Boston bombings and the Woolwich murder, involved unsupervised returnees – from Dagestan and Kenya/Somalia respectively – suggests an even greater effort is needed.

A second step is to distinguish between subsets of foreign fighters according to the rate by which they “produce” domestic attackers. This issue is not addressed in my article and will require new research and analysis. We do not yet know why some foreign fighters and not others move on to domestic operations. Nor do we know why some destinations produce more domestic attackers than others. The AfPak region, for example, has produced tens of foreign-turned-domestic fighters, while Somalia has hardly produced any.

Understanding these “determinants of differential returnee production” will be key to managing the future threat from the foreign fighters in Syria, a challenge that is not to be taken lightly. Just two years into the war, there may be over 500 Western Muslims fighting in Syria, more than in any previous Islamist foreign fighter destination, including the Afghan jihad in the 1980s. Most of these individuals are unlikely to pose a threat, but some will, so we should start thinking soon about who they are and when we might expect them. The most important indicator to watch is probably the declared strategic intent of jihadi organizations in Syria. If a group such as Jabhat al-Nusra should decide to systematically target the West, then the foreign fighter threat from Syria would increase substantially, as did the threat from Afghanistan when al-Qaida “went global” in the 1990s. In the meantime, we can take comfort in the finding that most jihadis choose foreign fighting because they do not want to be terrorists.

Now through June 15, 2013, my research from the APSR will be freely available to the public.