Both Audrey Kurth-Cronin and Barak Mendelsohn have written books that should be read. The two books approach the subject of terrorism from remarkably different angles, and each is most successful as a source of background information to crucial policy questions but least successful in providing guidance related to those questions. Both are polemical—each author has an axe to grind with previous research or policies—and perhaps because of this, in terms of policy guidance or implications, each makes its strongest contribution in negative form: as in “here is what has been missed,” or “here is what has been misguided” about previous efforts to understand terrorism in its transnational contexts.

Mendelsohn's central argument is that Hedley Bull's “English School” of international relations theory—which, in brief, imagines a society of self-interested states whose cooperative behavior cannot be reduced to the interests of any single state (or to coalitions of states)—is a useful lens through which to understand both the degree and quality of interstate cooperation in response to the threat of radical Islamic terrorism. Combating Jihadism is organized into two parts, containing a total of nine chapters. The first part of the book (Chapters 2–4) focuses on the nature of the threat to “international society,” and the second (Chapters 5–9) focuses on the nature of the international response to that threat.

The strength of the book lies in its insistence on the importance of nonmaterial factors—including shared norms and identities—in explaining interstate relations. The book also shines in its summary and review of both the English School's contribution to our collective understanding of international politics and such largely (and equally?) moribund theoretical traditions as hegemonic stability theory. Finally, Mendelsohn usefully reminds us that Al Qaeda's ideology is, in fact, far more ambitious in its scope than is captured by the majority of its public pronouncements about “Western influence” and troop deployments.

Three weaknesses of Mendelsohn's analysis work to undermine its strengths, however. First, the book is not designed as a contest between competing explanations. So, we wonder right away about the value added of the English School's approach as compared with simpler explanations. If we assume that states act in their own interests first, and later describe those self-interested acts as “benefiting all states” or “civilization,” then why could interstate cooperation not emerge and take place without the need for the elaborate intellectual superstructure of an imagined international society? The author argues not only that serious interstate cooperation is unusual but also that states intentionally act to defend international society. The difficulty is that there is no evidence adduced to support either claim, and in the absence of that support, it seems just as plausible to assert that the defense of this imagined society is a beneficial, yet unintended, consequence of the pursuit of narrow self-interest in the same way that a market is the beneficial, yet unintended, consequence of competition between modestly regulated and self-interested firms. So, it is not clear what we gain by using the lens of the English School to explain interstate cooperation in the years following September 11, 2001 (other than its rehabilitation as a going international relations perspective).

Second, Mendelsohn must demonstrate not only that Al Qaeda seeks the violent destruction of international society but also that its desire to do so is sufficiently threatening to activate and sustain societal agency. The argument takes the form of domino logic, in which a well-supported claim that Al Qaeda seeks to acquire and use weapons of mass destruction (WMDs) is conflated with the assumption that it will inevitably be successful in getting hold of and using them. Using WMDs is then necessarily assumed to constitute a threat to international society. But setting aside the question of whether Al Qaeda will acquire WMDs, why should we assume that WMDs would prove sufficient to destroy any particular state, or the state's system as such? Moreover, the author's own evidence supports an alternative explanation: The structure of the threat determines the structure of the response; so a transnational threat is, in most ways, best countered by a multilateral effort. His analysis reminds us that on threats that simply cannot be countered unilaterally (such as terror operations funding via global financial transactions), there is a great deal of interstate cooperation. It is simply not clear why this is surprising, nor why it might demand an English School perspective in order to appreciate.

Third, Mendelsohn runs into difficulties trying to remedy the gap between what the English School might predict by way of cooperation and U.S. unilateralism (particularly under the leadership of George W. Bush). In one of the book's stronger contributions, the author takes this threat to the English School head-on, showing that, in fact, the United States acted in ways that were constrained by its (social, not material) peers. Hegemony, Mendelsohn usefully reminds us, is about leadership, not necessarily belligerent domination. But the effort highlights a more serious problem: What if the society Bull conceived of as international is really Western society, and, by extension, the chief threat to Mendelsohn's attempt to reintroduce an English School utility is not great-power unilateralism (the lack of society per se) but the emergence of multiple international societies? True, Samuel Huntington's civilizations thesis has met with widespread criticism, but Mendelsohn's failure to engage Huntington's provocative thesis seems a lost opportunity.

Finally, granting Mendelsohn the benefit of the doubt for argument's sake, there is a demonstrably greater threat to international society than great-power unilateralism or Al Qaeda: failed states. This threat is related to Huntington's thesis because it suggests the possibility of rational actors who, for cultural reasons, simply prefer to live in political associations other than states. Or, rather, they choose not to undertake the sacrifices necessary (in particular, public service) to conduce to state formation. If, as Charles Tilly once summarized it, “war made the state,” then in the absence of a credible threat of conquest from other states, the relative costs of state formation (or maintenance) may outweigh the relative benefits; and this, more than any other factor, may explain why in the years since the end of the Cold War, “failed” states have become such a problem in so many places in the world.

These criticisms aside, Mendelsohn's book offers more than a few moments of brilliance, making it well worth a read. Whatever one thinks of his attempt to rescue the English School from relative obscurity, Mendelsohn's analysis of Al Qaeda's motives is among the finest in print

Kurth-Cronin's book is, in some ways, less satisfying than Mendelsohn's. While her previous work on the subject of terrorism has been outstanding, How Terrorism Ends proved somewhat disappointing. Even so, it remains a must-read for those interested in terrorism in its transnational contexts. At its core, this book aims to be an old-fashioned “those who ignore their history are condemned to repeat it” exercise. We are led to expect an analysis of a broad set of cases across time and space that results in useful policy recommendations. The book is divided thematically into six causes of the demise of terrorist groups historically, including 1) killing group leaders (decapitation); 2) negotiation; 3) success in achieving group objectives; 4) group failure; 5) state repression; and 6) group reorientation. The author's introduction aims to convince us (if we need convincing) that terror groups such as Al Qaeda constitute a “strategic threat,” and offers to weave together a history of previous efforts to end terrorism in order to develop an effective counterterror campaign against Al Qaeda.

The argument runs into difficulties almost before it gets started, however, because the book wavers between an assertion that contemporary terrorism is a grave threat to states and the interstate system due to significant advances in technology and the contradictory message that we have a great deal to gain from reviewing the history of terrorist groups now a century old. Moreover, for most of the intended audience of a book about a serious contemporary threat of harm, the question of how terrorism ends is not obviously interesting. What many who buy this book will hope to find is a book about agency: about what we can do to end terrorism.

Beyond this, there are really two main problems with the book. First, like Mendelsohn's and too many others, it traffics in domino logic: Kurth-Cronin shares the widespread assumption that Al Qaeda's acquisition of WMDs is inevitable, and as a result the threat the group represents now (negligible) is conflated with its intentions or ambitions (extreme). In other words, even in the absence of a capacity to enact political or superpolitical objectives, we must respond to those objectives (however grandiose) as if the groups advancing them already had the capacity to enact them. This is not to say that domino logic is not widely shared, or shared at high levels, in many governments (many thus claim that Iran is seeking a nuclear weapon, and when it acquires one it will be used, either by Iran or a shadowy terror group sponsored by Iran, and that it therefore makes sense to take risky, costly, or illegal action now). It is bad enough that this sort of domino logic has become conventional wisdom, but here Kurth-Cronin lends her authority to it in a way she resisted in her previous work. On the other hand, unlike Mendelsohn's core argument, whose validity rests on this domino-fed threat conflation, Kurth-Cronin's support for the same sort of threat conflation is meant to function merely as an incentive for paying close attention to the lessons she hopes to draw from her analysis of historical cases.

Second, the polemical aspects of the book are a constant distraction from its more insightful contributions. Kurth-Cronin is angry. This is entirely understandable. Like many of us who have been writing about asymmetric conflict since before 9/11, we have been forced to watch our government(s) willfully ignore the lessons of counterinsurgency history. The consequences of that willful ignorance have been calamitous: civil liberties abridged; an economy in ruins; our soldiers, sailors, and airmen killed and wounded; thousands of noncombatants maimed and dead; and our alliances frayed. But Kurth-Cronin's dismay, though understandable, sometimes gets the better of her. She thus succumbs to a tendency to advance the ideas of others without sufficient attribution (e.g.. Clausewitz's “trinity” idea in Chapter 1, or Max Abrahm's arguments about revulsion over terror targets in Chapter 4); and she tends to sound angry herself (e.g., “we would be foolish to slavishly follow a script written for an earlier age”; p. 193), even as she characterizes others as overreacting to the terror threat. These artifacts of her anger are unfortunate, because her previous work remains among the best scholarship in print on the subject of terrorism and counterterrorism.

Overall, the biggest shortcoming with How Terrorism Ends is that after walking us through a fascinating and useful history of terror groups and how these groups ended, Kurth-Cronin does not tell us much about how to end terrorism. Like Mendelsohn's Combatting Jihadism, her book is stronger on description than prescription. At the same time, both books offer the kind of insight that is indispensible to those working to craft effective policy responses to terrorism in its contemporary forms.