Enduring rivalries, long-standing militarized competitions between the same pairs of states (e.g., India and Pakistan), are perhaps the most dangerous phenomena in international relations, accounting for approximately three-fourths of militarized disputes and over 80% of wars. They also play central roles in increasing internal state capacity, and they consume enormous economic and political resources necessary to sustain them. These features make it essential, for theoretical and policy reasons as well, that we have a clear understanding of the conditions associated with the end of such hostile relationships and the malleability of those conditions. Unfortunately, as the end of the Cold War demonstrated, scholars and decision makers are often taken by surprise when enduring rivalries end. It is in this context that the present book is dedicated to the task of filling the huge gaps in our understanding about how and when enduring rivalries terminate.

Eric W. Cox's central argument is rooted in the idea that failures in policy prompt changes in preferences, which in turn expand the bargaining space in which rivals can agree to end their competitions. The first component in the model is domestic realignment that comes from a regime change or a new government within existing regime structures. Such changes stem from policy failures on the national level. The author provides examples of failure signals, specifically economic decline and political demonstrations, but there is no list of possible failures nor a specification of the scope of failure that is necessary to trigger the hypothesized effects. Problems stemming from national economic policy are a recurring theme, however, throughout the book.

Cox correctly notes that simple regime change is not necessarily conducive to rivalry termination. The direction of the regime change is as critical as the domestic realignment itself. If one hawkish leader replaces another, then there is likely to be little impact on the rivalry. There must be a movement toward leadership that is “moderate” or “dovish,” leaders who are more willing to make concessions and reach compromise with an enemy. The author suggests that change might be harder to resist in democracies than in more repressive regimes, but acknowledges that this proposition is not tested in the case studies. Still, the argument seems broadly applicable regardless of regime type, and as also posited in Charles Kupchan's recent work (How Enemies Become Friends, 2010), joint democracy seems far from necessary for rivalry termination, even as it can be a facilitating condition.

One of the important contributions of this work is bringing domestic politics into the study of international rivalry. Although there are periodic references to domestic political elements of rivalry, few studies address this directly. Cox tends to emphasize the domestic political conditions that are conducive to rivalry termination, perhaps not surprising given the focus of the book. Yet there is not enough attention given to the domestic political incentives to maintaining rivalries even in the face of policy failure. Michael Colaresi (Scare Tactics, 2005) notes that leaders can engage in “outbidding,” attempting to portray themselves as more hostile toward enemies than domestic opponents for political advantage and extended tenure in office. This might be expected to occur more frequently in the face of economic failure. Rivalries also become embedded in the bureaucratic and policy-planning processes of states, as well as the psychology of leaders and the mass public. Accordingly, one should not expect changes in rivalry to come so easily or quickly, even if all the specified conditions are present. Combined with the author's hypothesis that rivalry termination becomes less likely as the distance from the policy changes increases, this condition will produce an inherent stasis or resistance that is consistent with the punctuated equilibrium model of rivalries (see Paul Diehl and Gary Goertz, War and Peace in International Rivalry, 2000). This does not necessarily undercut the author's central argument, but it does suggest that the conditions cited might not have as strong a probabilistic effect on ending militarized competitions as is implied.

In Cox's view, domestic realignment that leads to rivalry termination is less likely to produce changes in rivalry dynamics unless it is accompanied by foreign policy failure. Domestic policy failure alone is not sufficient to alter rivalry dynamics, and foreign policy failures might not lead to changes in government if the domestic economy is healthy. The combined failures are said to produce a greater willingness to accept rivalry concessions, thereby opening up the bargaining space with a rival and make some kind of accommodation possible.

Cox zeroes in on multiple, simultaneous rivals as a driver of failure. Past rivalry research suggests that states might need to end one competition in order to concentrate on a new enemy, but this strategic choice element is not part of the rationale here. Instead, the author makes reference to resource pressures that stem from multiple rivalries. He nicely extends past work by arguing that resource strains, emanating from multiple rivalries, produce domestic policy failures as the government spends more on external rather than domestic needs; except perhaps for some analyses about the end of the Cold War, no one has made this “guns for butter” trade-off argument in the context of rivalry termination, and it is a welcome addition here.

Models of how rivalries end that depend largely on changes in one state run into the problem that rivalry termination is a joint decision, except for imposed military victories and total capitulations, outcomes that the author specifically and properly excludes. Where does the second rival come in when the conditions for rivalry settlement arise in the first rival? Cox provides two answers, almost as an addendum to the basic argument. The first is that the preference change of the first rival might lead its set of acceptable resolutions to be enlarged such that its bargaining space now overlaps with that of its rival; unfortunately, this is difficult to observe prior to any agreement. Second, the other rival might also experience similar domestic and foreign policy failures as well, thereby making it more receptive to its opponent's peace overtures. The author conceives of the termination process largely in single-shot terms, rather than as a series of reciprocal moves dependent on diplomacy. Accordingly, there is something lost when looking only at one end point and not the transition itself from rivalry to nonrivalry, something that is more evident in the case studies than in the theoretical argument. There is also no consideration given, albeit beyond the scope of the study, to the kind of relationships that exists after rivalry termination—“negative peace,” mere interruptions in rivalry behavior, or more peaceful interactions.

Hypotheses are tested via comparative case studies of paired rivalries that differ with respect to whether they terminated or not (Israel's rivalries with Egypt and Syria, and Peru's rivalries with Chile and Ecuador); these constitute four of the seven chapters. There are no new insights about the individual competitions per se, but the analysis is systemically done and largely confirms the author's argument. Self-declared measurement concerns and the likelihood of many false positives (economic downturns and foreign policy failures are common) make this work's primary value to be theoretical and heuristic, rather than empirical. Kupchan's book has received far more attention, but the present work deserves significant mention alongside of it as scholars grapple with what can be done to end enduring rivalries.