The Foreign Fighters’ Threat: What History Can (not) Tell Us

Methodological questions around the determination how many of the foreign fighters going to Syria are likely to engage in terrorism upon their return are discussed. Two approaches are used in this Research Note to assess the threat posed by Western foreign fighters in the past. These serve to answer two questions: how many of the former foreign fighters became involved in terrorist activity (approach 1) and how many of jihadist-inspired terrorists were former foreign fighters (approach 2)? The research is based on three studies (Afghanistan, Bosnia and Somalia) and the data are presented in an Appendix. A typology of foreign fighters is presented in the text itself.