This background paper is based on a presentation during a partnership for Peace Consortium (PfPC) Combating
Terrorism Workshop held in Brussels April 23-25, 2014 on the topic of foreign fighters. The paper discusses reasons
driving the phenomenon and highlights some legal responses taken by Western European states to stem flow of foreign
fighters to Syria and to reduce any potential disruptive activities upon return to their countries of departure. The current
foreign fighter mobilization in Syria is unprecedented in the number of individuals, nations represented and the speed of
the mobilization. Since foreigners flocked to Syria in late 2011 and early 2012, based on more than 1,700 primary and
secondary sources in multiple languages that have been collated, one can estimate their numbers at 9,000 individuals who
represent more than 80 nations. The bulk of these foreigners come from the Arab world and Western Europe with
approximately 5,000 and 3,000 coming from each region respectively. The vast majority have joined designated terrorist
organizations the Islamic State of Iraq and al-Sham as well as al-Qaeda’s preferred branch Jabhat al-Nusra.
Compared with the two prior top foreign fighter mobilizations since it became a phenomenon in the 1980s, the numbers
for Syria are much larger. They have occurred over a far shorter time span. From 1979-1992, it is believed that about
5,000 individuals went to Afghanistan for the anti-Soviet jihad. Additionally, during the last decade from 2003-2007,
around 4,000 foreigners decided to take up the cause of jihad during the Iraq war. In both cases, the numbers are about
half or a little less than half of what we have seen thus far in Syria. In Afghanistan the process spanned 13 years, while in
Iraq four years, and in Syria, just two years.
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