This book represents the culmination of a decade-long research focus on the idea that nations enter into specific patterns of crisis interaction, some of which are more likely than others to trigger interstate war. Paul D. Senese and John A. Vasquez set out to identify these dangerous patterns, using an iterative scientific approach to uncover the individual and cumulative roles of each (mis)step in crisis dynamics. In particular, they examine why the existence of territorial issues can combine with the evolution of repeated disputes to elevate the risk of war. The result is largely successful, and Senese and Vasquez provide a valuable contribution to our understanding of how wars occur.

The study of war is well established, of course, and the authors do a wonderful job of grounding their work within the broader literature, as well as the specific efforts that focus on quantitative empirical indicators of war. I found myself wishing I had this book when preparing for exams back in my graduate school days. It is sure to become a standard in any advanced undergraduate or graduate course on conflict processes. What sets this book apart from extant works is the ability of the authors to demonstrate the impact of the combination of territorial issues and repeated disputes. Put simply, “When all is said and done what really increases the probability of war is not the mere presence of territorial issues, but how they are handled” (p. 175). The emergence of territorial issues between states places the dyad in a dangerous position, but how leaders negotiate these issues over time becomes as important as the initial problem.

This insight is nontrivial, and it has two important implications for research on conflict processes. First, even though each factor matters independently, it is the interaction between rivalry and territorial issue salience that maximizes the probability of escalation to violence. We can step back to observe this interaction abstractly as one between initial conditions and process. The presence or absence of territorial issues represents an initial condition that is not strategic, at least within the context of the immediate crisis (one can easily imagine that the existence of territorial issues can become a strategic issue in its own right, but the manipulability of territorial salience is one example of a research question that is motivated by the book). The interactions that divide settled disputes from enduring rivalries are political and strategic. Previous research on territory and conflict tends to load the explanatory power on the initial conditions (the existence and character of territorial issues). Previous research on rivalry underemphasizes the interaction between initial conditions and the rivalry process. This book integrates and extends the research by Paul Diehl and Gary Goertz (War and Peace in International Rivalry, 2000), Paul Huth (Standing Your Ground: Territorial Disputes and International Conflict, 1996), and Russell Leng (Interstate Crisis Behavior, 1816–1980: Realism vs. Reciprocity, 1993) to provide a more complete picture of the danger that states face when dealing with the dual problems of territory and rivalry.

Second, power politics broadly understood as “peace through strength” have served nations poorly over the last 200 years. In situations where conditions are ripe for an escalation to violence, the pursuit of power politics triggers the use of force, rather than deterring it. This result seriously contradicts the conventional wisdom that shaped foreign policy decisions throughout the twentieth century. If territorial issues can be resolved instead of repeatedly motivating disputes, the result can be a lasting, robust peace. In other words, territorial disagreements are not a sufficient condition for war, and the adoption of realpolitik strategies to resolve such disagreements appears to be the “step” to be avoided. Acceptance of borders is a central element of peace between neighboring states.

The book is sure to raise questions about the causal mechanisms connecting territory and war, and I expect to see both empirical and theoretical responses. On the theory side, it raises the question of why leaders fail to successfully navigate the troubled waters of territorial disputes, as well as why the emergence of an enduring rivalry alters the crisis bargaining process to the detriment of peace. On the empirical side, while the authors make a strong case with their use of large-n quantitative analyses, the steps-to-war argument is ultimately one of process and escalation. As such, I can envision a multitude of complementary studies that use process tracing and case histories to examine these escalation dynamics. There would be value in demonstrating how the presence of territorial issues exacerbates the crises that can lead to violence. That is not to say that the empirical results herein are on shaky ground, but rather that the broad analysis in the book can serve as a framework for studies of the specific policy dynamics that emerge when territory and rivalry are present. If we can compare such cases to the policy dynamics that are present in other types of crisis negotiations, we may make more progress toward understanding why rivalry and territory make such a dangerous combination.

Overwhelmingly, however, this book is an exemplar of empirical peace science. The combination of a well-established theoretical argument with transparent quantitative research design in an iterative fashion generates clear and lasting research. The text is accessible to a wide audience without sacrificing rigor or innovation. The scope of the work is impressive, and the authors rise to the broad challenge of assessing war throughout the international system. For Paul Senese, whose service to the peace science community and commitment to peace research ended unfortunately too soon, it is a fitting, albeit unwelcome, coda that will continue to inspire us as we endeavor to unravel the enduring problem of international war.