Why do some civil wars look like traps with no way out, long after fighting has stopped being worth it for anyone? In this ambitious book, Jonah Schulhofer-Wohl takes on this important question and provides an important answer. Quagmires, he argues, are not inherent to some civil wars. They are instead the product of interlocking strategic decisions by belligerents and their foreign backers. Schulhofer-Wohl defines quagmires as conflicts in which a belligerent suffers more than it gains in continuing to fight, but nevertheless concludes that conceding would be worse. A quagmire is caused by two mechanisms. First, external support keeps belligerents fighting when they would otherwise throw in the towel. But they do not try to strike a knockout blow either, by taking and holding territory, because doing so is too costly. So, in a second mechanism, these belligerents opt instead for a kind of relatively low-cost (but still terrible) mode of war, with bloody but desultory clashes to no real end. Nobody wins, but nobody concedes either.

Schulhofer-Wohl first develops this argument in a game-theoretic model. He then analyzes the Lebanese civil war, drawing on some 150 hours of interviews with faction members to examine how plausible these two key mechanisms are. He productively focuses on key turning points, in which weak factions choose not to concede because of foreign backing, and strong factions choose not to try to win because of the costs of escalating. Next, Schulhofer-Wohl tests his model in a cross-national statistical analysis that examines why some civil wars are much longer than standard correlates of civil war duration would predict. Finally, he presents two briefer case studies, asking why a country as different from Lebanon as Chad is experienced a quagmire (1965–94), whereas a country as similar as Yemen did not (well, in 1994, at any rate). In the conclusion, Schulhofer-Wohl makes an appeal against foreign policies of half-measures, such as the United States’ attempt to find a middle ground in Syria—avoiding a loss but never going “all in” (p. 213).

There is a lot to learn from this book. It is an important contribution to the study of the macro-strategy of civil wars and should find its way onto graduate syllabi for that reason. It is especially enlightening about external sponsors. Like much of the fast-growing body of scholarship on outside actors in civil conflicts, Schulhofer-Wohl takes on the agency problem these sponsors face in trying to induce clients to adopt costly war-winning strategies. But he goes a major step past earlier work, arguing that as outside sponsors try to avoid both this agency problem and foreign-policy losses at the same time, the low level of support they wind up giving is enough to keep a war dragging on. This is an important corrective to images of the innocent abroad, making clear how external actors are complicit in creating quagmires.

The model also yields some innovative hypotheses, which are counterintuitive at first glance. The most notable is probably that, given outside sponsorship, wars can drag on even though (in fact, because) it is costly and difficult to bring about a victory that seems to yield little benefit anyway. Finally, the different types of empirical analysis yield a number of different observations that are consistent with the approach, and the book’s progression from mechanisms to cross-national analysis to confirmatory embedded case studies is logical.

However, there is a good deal to be improved on here as scholars carry on studying quagmires. There are some major omissions from the theory and so some important unanswered questions. Of course, it is too easy for a reviewer to call for more complexity, and each of these omissions can be justified on parsimony grounds. But these issues are important enough that leaving them out requires an explanation. First, it is unclear why nonterritorial fighting helps a weak belligerent avoid defeat. The kinds of live-and-let-live arrangements that Paul Staniland highlights (“States, Insurgents and Wartime Political Orders,” Perspectives on Politics 10 [2], 2012) seem like another option—not laying down arms, but not paying the bloody costs that motivate this book either. Second, foreign players are construed only as backers, not as belligerents in themselves. So, the model makes no distinction between supporting a local ally and sending in a major combat operation of one’s own. But this outside option—so central to quagmires in Iraq, Afghanistan, and Vietnam—looks at first glance like a way around the agency problem and thus should have a major effect on the strategy of the entire game, if it gives the outside backer the option of doing what it does not trust its client to do and adopting a high-cost strategy itself. As it happens, in the course of the case study, Schulhofer-Wohl treats Syria as a belligerent in its own right in 1978, but how this reshapes the strategic game is not clear.

The book’s qualitative material is most convincing when it comes to the idea that parties often keep the war going because they expect (or are receiving) foreign help. There is, unfortunately, much less empirical work here on the outside sponsors themselves. Although Schulhofer-Wohl offers a clear portrait of the objectives that states like Israel and Syria were seeking in Lebanon, what is missing is how these actors weighed their objectives against the costs of fighting and the strategies of clients. In that sense, the book does not quite cash out its ambition to analyze quagmires as the consequence of strategic interaction, because it leaves one side of the interaction underexplored.

Finally, it would help to have a more thorough discussion of the links between quagmire and military operations. The model appears to assume that high-cost, territorial warfare forces a resolution and so does not produce quagmires. To say the least, this merits a discussion. Would high-intensity operations really be any better? Would the classic response of guerrilla warfare not seriously limit this strategy? Schulhofer-Wohl indeed thinks it does: he argues that Syria did not try to take territory in East Beirut in a 1978 turning point because of the prospect of guerrilla resistance (pp. 121–22), and his statistical analysis treats factors assisting guerrilla tactics as a key element of the cost of escalation (p. 162). The assumption, then, is that strong actors take this prospect and its costs into account (this is a perfect-information model, after all) and choose not to try to take territory. But plenty of quagmires seem to have resulted from states that mistakenly thought they could power through guerrillas with high-intensity strategies.

Thus, this book argues that quagmires emerge from doing just enough not to lose and not to let one’s clients lose. However, it leaves unconsidered the possibility that quagmires could come from trying to win, thinking you can, and discovering you cannot. When the policy advice is basically to go big or go home, it needs to be sustained by a clear sense of what going big looks like and what quagmires it can create.

But this objection nevertheless accepts the core element of Schulhofer-Wohl’s argument, which is a valuable one. Quagmires are not things that exist for outside actors to fall into. Rather, those outside actors help set the traps themselves, and everyone gets ensnared.