The phenomenon of foreign fighters serving with (mainly Sunni) jihadist, Islamist militias is well known to researchers. Its most famous manifestations, until the last decade, were the "Afghan Arabs," citizens of Arab countries—including Osama bin Laden—who took part in the war against the Soviet occupation of Afghanistan. Interest intensified when large numbers of Islamists from Arab and Western countries joined with the Islamic State (ISIS) after it declared its "caliphate" in June 2014. But much media coverage of ISIS volunteers has been sensational and superficial: Byman provides a comprehensive history of the foreign-fighter issue and grapples with the important question of how Western countries can combat and eliminate it.
Road Warriors provides a concise and ordered survey of the foreign fighter phenomenon, noting that Sunni Islamism was not the first or only political movement to use foreign volunteer combatants. Byman surveys the Afghan experience and notes the crucial role of Abdullah Azzam, a Palestinian pioneer of Salafi jihadist military activity, in laying the ideational and organizational foundations for what eventually became al-
Qaeda. The author looks also at the foreign fighters' role in the Chechen war, in Africa, and in the context of the Sunni insurgency against the U.S.-led occupation of Iraq. The book then turns to the recent Syrian and Iraqi experiences.
Byman's research is most valuable as the first attempt by a serious researcher to deal in detail with the particular appeal of ISIS for foreign jihadists. As he notes, more foreign fighters travelled to Syria and Iraq than to all previous jihads combined—about 40,000 fighters. Byman discusses the role of social media and notes that while ISIS has now declined, the movement has "nurtured the flame of jihad around the world." Other movements will seek to "harvest what Islamic State planted." He concludes by offering tentative advice for Western policymakers, concluding that as the rise in the appeal of jihad was not predicted, it is also impossible to trace a timeline for its eclipse and decline.
Road Warriors is a comprehensive, readable, and informative addition to the literature. Hopefully, it will lead to further focus by researchers on the lessons to be
learned from the astonishing, rapid success (and equally rapid eclipse) of the Islamic State.