LAUSR

Joshua Kertzer’s important and impressive new book begins with the observation that the concept of resolve is frequently used as an explanation for international events. The idea of resolve is particularly prevalent in the international security literature, as it is used to explain deterrence success or failure and the outcome of crisis bargaining and military conflicts. However, as Kertzer points out in Resolve in International Politics, “resolve” has neither been clearly defined nor carefully studied. The rational choice literature has defined resolve in differing ways, some of which overlap with other concepts, such as military capabilities. In the broader scholarly and public dialogue, resolve is often not defined at all, but is used as a “catchall residual” (p. 3) explanation for international outcomes when other explanations fail. Clearly, the differing and sometimes casual uses of the word “resolve” make it difficult to study the concept using social science methods. Therefore, Kertzer does the discipline a great service by delving into the details of what resolve is and where it comes from. His basic definition of resolve as “firmness or steadfastness of purpose” (p. 8) is simple and follows theOxford English Dictionary. However, he ultimately goes far beyond this by offering a comprehensive account of the factors that contribute to resolve. Kertzer begins his discussion of the sources of resolve by noting that resolve can be viewed as a dispositional attribute, stemming from an actor’s character, or as a situational attribute, driven by the incentives and costs that an actor faces. Focusing specifically on resolve in the context of military interventions, he proposes an interactionist theory of resolve that incorporates both situational and dispositional factors. The situational factors that affect resolve are the costs of fighting and the costs of backing down, which include both reputational costs and the intrinsic interests at stake. The dispositional factors are time preference, risk preference, honor orientation, and trait self-control. By incorporating both situational and dispositional factors into his theory, Kertzer is able to offer insight into how dispositional attributes moderate the effect of situational incentives. The empirical section of the book has two main parts. The first part is concerned with testing the author’s theory of the factors that influence resolve and uses resolve as the dependent variable. Kertzer begins with a laboratory experiment administered to university students. The participants were presented with a scenario about a hypothetical military intervention and asked their opinion about whether to initiate the intervention and then whether to continue it. In the experiment, he manipulated various situational factors and also collected information on participants’ dispositional attributes. In addition, he presents the results of a similar survey experiment that he performed using a national sample. Across both the laboratory experiment and the survey experiment, Kertzer finds that situational factors do affect resolve, but the effect of dispositional factors on resolve is even stronger and more consistent. The second part of the empirical section focuses on how resolve impacts the outcome of military interventions by great powers. In this portion of the book, resolve is the independent variable. Having already established which factors are sources of resolve, Kertzer is in a good position to measure resolve without resorting to tautology. Using a Boolean logit model, he incorporates all of the situational and distributional factors discussed previously. Due to limitations on the information available, rougher measures of these concepts are employed in this part of the analysis than in the experimental part. Nonetheless, Kertzer’s measurement choices are plausible, and he employs multiple measures of the same concept so that the results do not depend on a single measurement choice. The key takeaway from this second part of the empirical analysis is that resolve does increase the probability of victory. In particular, Kertzer finds that reputational costs for backing down, as well as leaders’ time preferences and honor orientations, contribute to the probability of victory. As he himself notes, the apparently smaller impact of some of the other variables could be due to less appropriate measures (p. 139). On the whole, this book makes several groundbreaking contributions. It provides the most thorough discussion to date about how to conceptualize resolve, it provides evidence of which dispositional and situational factors contribute to resolve, and it provides the strongest evidence yet that resolve itself influences conflict outcomes. The ultimate finding—that resolve matters— is in keeping with common belief, but we can be much