American Political Science Review

Research Article

Should I Stay or Should I Go? Explaining Variation in Western Jihadists' Choice between Domestic and Foreign Fighting


Norwegian Defence Research Establishment (FFI)


This article studies variation in conflict theater choice by Western jihadists in an effort to understand their motivations. Some militants attack at home, whereas others join insurgencies abroad, but few scholars have asked why they make these different choices. Using open-source data, I estimate recruit supply for each theater, foreign fighter return rates, and returnee impact on domestic terrorist activity. The tentative data indicate that jihadists prefer foreign fighting, but a minority attacks at home after being radicalized, most often through foreign fighting or contact with a veteran. Most foreign fighters do not return for domestic operations, but those who do return are more effective operatives than nonveterans. The findings have implications for our understanding of the motivations of jihadists, for assessments of the terrorist threat posed by foreign fighters, and for counterterrorism policy.


Thomas Hegghammer is Senior Research Fellow, Norwegian Defence Research Establishment (FFI), P.O. Box 25, 2027 Kjeller, Norway (


  I thank Scott Gates, the APSR editors, and the anonymous reviewers for very useful comments on early drafts of the article. I also received helpful comments and advice from Kristin Bakke, Jeff Colgan, Lynn Eden, Karen Greenberg, David Laitin, Brynjar Lia, Yassin Musharbash, Vipin Narang, Petter Nesser, and Truls Tønnessen. I presented early versions of the article at University College London, the University of Aberdeen, and Stanford University; I thank all the participants in these seminars for helping improve the article. I am grateful to Stanford University's Center for International Security and Cooperation for the Zuckerman Fellowship that allowed me to complete the article.