The system of equations developed in the book cannot be solved analytically, and thus Kadera turns to numerical solutions through the use of simulations. She makes a variety of assumptions about the values of the various parameters of the model (pp. 68–81), and then randomly generates 50 different sets of initial conditions. Three distinct patterns emerge in the simulations, which she labels the bull and gnat (B&G) transition, the tortoise and hare (T&H) transition, and the David and Goliath (D&G) transition. The deductions for each of these transitions are nicely summarized in Table 6 (p. 106).

Several important conclusions can be drawn from the model. First, Kadera demonstrates that a challenger is more likely to succeed if its growth is more evenly paced and if the challenger is less sensitive to his opponents' attempts to reduce the challenger's power through conflict. Second, she shows the conditions under which each side will be more or less conflictual toward its rival. For example, she demonstrates that Davids and Goliaths take turns being the more conflictual contestants, which is quite different from the PT focus on the challenger as the more aggressive state. Finally, her model predicts that two rivals' conflict levels will become coupled over time, such that both sides are responsible for the path that leads them to war. This helps to reconcile the claims by BOP scholars that the more powerful nation will attack with the claims by PT scholars that the rising challenger is more likely to attack.

There are several things I really like about this book. First, although the model and simulations are fairly complex, Kadera does a wonderful job communicating her ideas clearly throughout the book. Second, her summary of the theoretical and empirical research on the BOP and PT theories (Chapter 2) is excellent and could be used independently in an international relations graduate course. Third, she does an admirable job providing a substantive interpretation for each parameter in her model. Fourth, I am very persuaded by her assertion that we should model the relationship between power and conflict in a manner that captures both endogeneity and dynamics. IR scholars have a tendency to examine the impact of power on conflict, or the subsequent impact of war on power, but it is rare to find a model like Kadera's that captures the evolution of this relationship over time. Finally, the inclusion of conflict as an explicit variable in her dynamic model avoids earlier problems encountered in the research of Lewis Fry Richardson and Charles Doran, where the conditions for war are inferred from the dynamic process of the power-based variables, and not modeled explicitly.

One limitation of the simulations is an assumption that the specific (or instantaneous) growth rates of the two sides are equal. This assumption makes it difficult to assess any differences that stem from one state's advantage in converting existing power into greater future power. For example, one state may have a greater endowment of national resources or more efficient production processes than its rival. It would be interesting to see how the deductions from the model changed if one side's specific growth rate exceeded its rival's specific growth rate. Kadera allows for most other parameters in the model and the initial conditions to be larger for one side in comparison to the other. It is not clear how the results would be altered if the differences in these parameters diminished. For example, it would be useful to demonstrate how the conclusions are altered as each set of parameters is varied from a stage of equality to large asymmetry. Kadera does conduct such an exercise with respect to the beta parameters (with higher values representing more salient issues), but the reader is left wondering how the results would change as the other parameters in the model are varied.

One other objection I would raise regards Kadera's decision to limit her empirical tests to major power dyads, and to employ the Militarized Interstate Dispute (MID) dataset. As she notes, her conceptualization of conflict as a continuum (with war at one end and cooperation at the other) does not match her empirical measure of conflict well (based on the number of MIDs between rivals). Her decision to employ the MID data was based on the lack of major power transitions in the years covered by events datasets, such as COPDAB (1943–78, three major power transitions) or WEIS (1966–78, one major power transition). On the other hand, it would have been nice for her to test the model in a set of minor power dyads in this more limited time period, for which data was available. She points out (p. 112) that the model could be generalized to other types of competing dyads, and such a test would have provided additional support for the model and would also have captured the cooperative end of the spectrum, which she is interested in.

In summary, The Power-Conflict Story is a compelling tale of interactions between rival states over time. It not only helps to resolve an ongoing debate in the field by showing that both BOP and PT theories are right under certain conditions, but it also produces a series of new theoretical hypotheses. In this regard, Kadera's theory meets Imre Lakatos's criteria for explaining the content of previous models and predicting new or novel facts. Such progress in the study of international relations is commendable.