The study of mass violence and civil war is increasingly taking a turn toward the micro level. Academics like Stathis Kalyvas stress the importance of examining violence district by district or even by village by village. Motivations of greed and grievance against neighbors, Kalyvas argues, are often far more consequential in driving violence than the grand ideological claims made by political elites. Meanwhile, David Kilcullen, a mandarin of counterinsurgency policy and close advisor to the U.S. military, stresses the need to identify local solutions to local problems of political order. Yet some of the most spectacular and horrific acts of destruction, including suicide bombings in Syria, Iraq, Afghanistan, and Somalia, have been perpetrated not by local forces settling local grudges but by outsiders. The prominence of Lebanese and Iraqi militants in Syria, for instance, is perhaps easily explained by the artificiality and permeability of national borders in the region. Local politics, in these cases, may be necessarily cross-border. More puzzling, though, is the willingness of certain small cadres from Europe, Australia, Canada, and the United States to fight and die on distant battlefields.

David Malet is the first scholar to take on the phenomena of foreign fighters in a systematic, comparative, and empirical way, although there have been studies of particular conflict cases in which foreign fighters have been prominent, especially those cases associated with Islamic radicals, such as Afghanistan, Chechnya, and Iraq (see Thomas Hegghammer, “The Rise of Muslim Foreign Fighters: Islam and the Globalization of Jihad,” International Security 5 [Winter 2010/11: 53–94]). In contrast to the emphasis on instrumentalism and opportunism that has come to dominate the study of civil war violence, Malet deploys social movement and framing theories that emphasize emotions and nonrational responses (Chapter 1 of Foreign Fighters). While some foreign fighters are no doubt adventurers or seekers of plunder, the dominant method for recruiting foreign fighters is to claim that a given transnational community, be it ethnic or ideological, faces existential threat. In Chapter 2, Malet presents a newly constructed data set on the prominence of foreign fighters in different kinds of civil wars. Making effective use of descriptive statistics, he shows that foreign fighters are not novel and certainly not unique to conflicts of the Islamic world. In fact, of the 331 civil conflicts he codes, over 20% had foreign fighters. Differentiating between ethnic and nonethnic conflicts, he develops a very useful typology of foreign fighter types: 1) Diasporans join with nationalist rebels in ethnic conflict to advance common nationalist goals; 2) liberationists defend anticolonial rebels to advance shared ideological goals in nonethnic wars; 3) encroachers are coethnics involved in nonethnic conflicts; they join with secessionist rebels in adjacent states to expand political control; and 4) true believers join ideological rebels to preserve institutions of shared transnational identity.

The core of the book comes in the subsequent chapter-length case studies examining each of these types in turn. Chapter 3 deals with the flood of Anglo-Americans who joined the Texas Revolution, Chapter 4 with the foreigners who joined the Nationalist and Republican sides of the Spanish Civil War, Chapter 5 with the recruitment of outside Jews, Muslims (and occasionally Christians) during Israel’s War of Independence, and finally, Chapter 6, with the role of Muslim fighters in Afghanistan’s civil war. These case studies further illustrate the diverse forms that foreign fighters can take while also emphasizing the commonality in efforts to appeal to recruits based on a notion of shared transnational threat. Foreign fighters, therefore, appear to be less driven by greed than by grievance and think of themselves as engaging in a distinctly defensive mobilization.

Malet concludes by addressing a key policy concern: the fear that foreign fighters might return from the battlefield to carry on the fighting at home or elsewhere. In fact, he argues, in most historical cases foreign fighters readjust to home life relatively easily. The problem is that following the Afghan civil war, Arab governments unwittingly blocked the road to reintegration by refusing to allow their citizens to return for fear of hastening radicalization at home. Instead, Afghan Arabs became a kind of metastasis, carrying jihad to the farthest corners of the world. Stopping the recruitment of foreign fighters can only come about when states reduce “the centrality of transnational groups as social structures in the lives of the recruits and replacing them with the institutions of citizenship instead.” Governments must strive to “build the appeal of national civil and military institutions to facilitate greater identification with the state and fellow citizens” (pp. 212–13).

Dan Miodownik and Oren Barak’s edited volume picks up on the themes of the fuzzy borders of national identity and uncertain power of states as driving the transnationalization of conflict. As is usually preferable in a work with multiple contributors (including Malet himself), the chapters of Nonstate Actors in Intrastate Conflicts move in the same general direction, but not in lockstep. Barak and Chanan Cohen make a key theoretical contribution in their description of a modern “Sherwood Forest,” comprised of the overlap of universal ideologies, violent actors, and zones of statelessness (p. 15). But other violent transborder nonstate actors also inhabit this forest. While foreign fighters might consider themselves Robin Hoods, committed to goals like universal justice and emancipation, nationalist liberation movements and filibusters exploit the same anarchic space in pursuit of more localized, narrow agendas. Pirates, privateers, and other criminal groups similarly use these spaces to pursue material gains. Barak and Cohen conclude that international policy must focus on maintaining state power to prevent utter anarchy. Since restraining rogue states is easier than rebuilding failed ones, the international community must seek to reform but also reinforce state power, even in places where leaders pose a threat to global security. At the same time, they reinforce Malet’s point by contending that states must also “open their political systems to incorporate [dissident] actors” and thereby defuse the urge to mobilize transnationally (p. 32).

The volume’s empirical chapters are drawn exclusively from the Middle East, an understandable but somewhat unfortunate choice. The Middle East is indeed replete with all manner of transnationalism actors, some of whom are violent. Yet this geographic focus also reinforces preconceived notions about the shallowness of national identity in the Middle East without recognizing that other regions have experienced much the same kind of contestation over the limits of national identity. Still, each chapter is worth reading on its own. Avraham Sela and Robert Fitchette return to the influential case of the Afghan Arabs, highlighting the potent mix of state intervention and benign neglect that drove both the emergence of this cadre of foreign fighters and their subsequent dispersion. Gallia Lindenstrauss examines Turkey’s policies toward Iraq in light of concerns about the violent Kurdish transnational activities. The extent to which the Kurdish diaspora is securitized in Turkish political discourse directly affects the way Turkey has responded to the various kinds of violence on its southern border. Sela and Barak’s chapter on the interactions of domestic and regional levels in the Lebanese civil war and Orit Gazit’s study of the South Lebanese Army, which collaborated with the Israeli occupation, further emphasize how porous boundaries, weak national institutions, and contested national identities turned Lebanon into a kind of transnational hub. Gabriel Sheffer takes a slightly different turn, contending that coethnicity and diaspora kinship are distinctive factors driving the transnationalization of civil conflict. This argument is further developed empirically in Nava Löwenheim’s chapter on the role of the militant Armenian diaspora in defining Turkish-Armenian relations.

Ultimately, both works make significant contributions to the study of conflict. Malet’s book is agenda setting, and Miodownik and Barak’s volume offers an effective elaboration. Given this success, it is time to expand the agenda. The two books offer a fount of interesting, important, and plausible hypotheses, but they stop well short of really testing them. In part, this is a limitation of data quality and availability. As Malet points out, we know very little, for instance, about efforts to recruit foreign fighters that failed. But there are other outstanding questions as well: For example, what impact do foreign fighters have on civil war outcomes? Malet shows quantitatively that foreign fighters are involved in a disproportionately large number of rebel victories, evidence perhaps that foreign fighters contribute to increased combat effectiveness. But there could well be endogeneity in this relationship, with foreigners choosing to fight only in wars when they think there is a good chance of winning.

The lack of firm empirical findings about the causes and consequences of foreign fighters should chasten the natural tendency to offer policy advice. Malet’s and Barak and Cohen’s recommendations for dealing with radicalization of foreign fighters, for instance, more or less parallel the general recommendation that political opening is a way to assuage and channel violent discontent. But the empirical basis for this conventional wisdom is hardly settled. Even if it is correct at the domestic level, foreign fighters seem to fit a very different profile than the more commonplace homegrown radical. For one, they have greater attachment to transnational ideologies and a broader worldview. For another, they seem to be more accepting of risk than the regular “local” fighter. Overall, then, domestic reform may not necessarily have the same pacifying effect. In-depth qualitative analysis of a more diverse group of conflict cases and more intensive quantitative analysis are clearly in order. Until we know more about foreign fighters, it is probably best to avoid venturing prematurely into policy prescriptions. At the same time, the books under review are important contributions to the further development of such knowledge about the role of foreign fighters in intrastate conflicts.