Book excerpt: Recent wars in Eurasia have foregrounded the flows of foreign fighters between distinct insurgent battlefronts. Since 2011 thousands of individuals have travelled from the Caucasus and Central Asia to fight in Syria and Iraq. Caucasians have also appeared in the fighting that followed Ukraine’s Euromaidan Revolution in 2014. Resolutions of these conflicts promise further movements as foreign fighters return home. This collection of articles presents for the first time in one volume a cross-regional comparative perspective on the trajectories of foreign fighters between the Caucasus, Central Asia, the Middle East and Ukraine. Drawing on extensive primary sources, contributors theorize the life cycles of foreign fighter waves and the respective roles played by pre-existing insurgent networks, transnational ideologies such as "global jihad" and "Eurasianism", and propaganda framing by insurgent groups such as the Islamic State. They examine regional state responses to the security threat posed by foreign fighters, showing how current security governance regimes can reinforce insurgent ideologies attracting violent militants. Finally they investigate the motivations for foreign fighters to return to their home states in the Caucasus and Central Asia. Arguing for the networked character of insurgencies in Eurasia, this book offers a unique overview of the foreign fighter phenomenon across the continent. It was originally published as various special issues of Caucasus Survey, Terrorism and Political Violence and Studies in Conflict & Terrorism.