The book is divided into four parts. The first offers an overview of the history, progress, and underlying issues of the Correlates of War (COW) and International Crisis Behavior (ICB) projects. The second examines factors that bring about war; the third, factors that promote peace; and the fourth and final part offers up some lessons and conclusions. The first part is particularly useful for undergraduates and first-year graduate students. In three chapters J. David Singer, Stuart A. Bremer, and Micahel Brecher, Patrick James, and Jonathan Wilkenfeld—prominent pioneers in the quantitative study of war—provide a good overview of the background, progress made, and questions that still need to be addressed by the COW and ICB projects. It is somewhat surprising to find that the contributors to this volume are strikingly modest in their claims about the success of the program. When Bremer assesses progress in attempts to answer the questions “Who fights whom, when, where, and why?” he feels compelled to “admit that this has not been a very successful endeavor” (p. 35). (See also Zeev Maoz' caution in his chapter on alliances [pp. 112, 137].) Singer's discussion of assumptions and some metatheoretical considerations offers good advice and food for thought for graduate students. In the third chapter, Brecher, James, and Wilkenfeld assess the progress of the ICB project and make some short comparisons of their findings with the COW findings. This is one of many instances where new insights from rational choice theory should have been discussed. James D. Fearon (“Signaling Versus the Balance of Power and Interests—An Empirical Test of a Crisis Bargaining Model,” Journal of Conflict Resolution 38 [June 1994]: 236–69) has argued that ex ante observable characteristics such as military power should play a fundamentally different role in situations before and during crises. Except in the excellent chapter by Jack Levy, fundamental problems such as selection effects and endogeneity are barely discussed. (To be fair, Paul K. Huth, Gary Goertz and Paul F. Diehl, and James Lee Ray briefly address some of these issues in their chapters.) This is regrettable since these issues are coming to the front of the field.

The second group of essays discusses factors that bring about war. These nine chapters offer a nice mix of new and emerging research agendas (or variables), such as the role of territory and enduring rivalries in international conflict, and more established research agendas, such as the role of alliances, capabilities, military buildups, and escalation. The chapters by Paul R. Hensel and Paul K. Huth are among the best in the book and form a particularly nice match. Hensel carefully and instructively unpeels several layers of the onion and offers several original empirical analyses on the relationship between territory and war. He finds that “[t]erritorial claims appear to be a leading source of militarized conflict and war, increasing both the likelihood [and] … severity levels of [militarized conflict]” (p. 81) While Hensel analyzes new data and proposes new hypotheses, Huth offers a rich and subtle discussion of theoretical explanations for the role of territory in conflict. The chapters on alliances by Zeev Maoz and Douglas M. Gibler consider a broad range of factors affecting how alliances can promote peace and war. The chapter by Maoz presents an especially thorough overview of the role alliances have played, with extensive tests and replications of the main propositions. Gibler proposes a reconceptualization and new typology of alliances and some initial tests. The two chapters, by Goertz and Diehl and by Frank Whelon Wayman, on rivalries offer only limited empirical evidence on the role of (enduring) rivalries but provide a good discussion of this emerging but relatively neglected research agenda. Russell J. Leng's chapter on crisis escalation is a clear instance where the book achieves its goals. Since it is impossible to keep up with all the literature on conflict, I had missed Leng's earlier work on crisis escalation. He presents a very interesting typology of crises based on both realist (rationalist) and psychological factors. He finds that “[v]ariations in the crisis structure are strongly associated with whether the crisis escalates …” and “that any examination of dispute escalation that does not consider its dynamic character is incomplete” (pp. 247, 256). Daniel S. Geller's chapter on material capabilities unfortunately highlights this book's failure to examine the links between the existing quantitative research and more recent formal work. Thus, while Geller broadly discusses the role of status quo orientations, no attempt is made to evaluate the empirical work in light of recent extensive work on status quo orientations and war, as, for example, by Robert Powell (In the Shadow of Power, 1999).

Part III of the book examines factors that promote peace and includes a chapter on international norms by Raymond and a chapter on democracy and war by Ray. The chapter on international norms discusses mainly theoretical concerns about norms and their effects; little attention is paid to the rich empirical literature linking norms and the democratic peace. Ray examines the empirical literature that links democracy and war with a careful eye on potentially confounding variables and spurious correlations. His discussion does incorporate the contributions made by the formal literature.

Three chapters, by Levy, Manus I. Midlarsky, and Vasquez, summarize the findings presented in the preceding chapters and offer conclusions on the progress of what is referred to as the “scientific study of war.” Although brief, Levy's chapter stands out in this book as an excellent primer for future empirical research. Levy discusses emerging issues and concerns in the study of war, paying attention to new insights from the formal literature and constructivist approaches. He discusses how these insights affect and impact the quantitative study of conflict. To name but two of these, Levy offers brief but insightful discussions of the poor efforts in much of the quantitative study of war to understand and incorporate interaction and selection effects fully.

Most chapters clearly point to a lack of good theories to explain the relationship of the author's preferred variable to the variation between war and peace, and so it is all the more surprising that so little attention is paid to the emerging formal literature. Overall, however, I would recommend this book to new graduate students. Some of the chapters are excellent starting points for students surveying the existing quantitative literature on international conflict and for students starting their own research. Regrettably, there is a distinct trend toward Balkanization in international relations. A not-to-be-underestimated quality of this book is that it makes it easier for those interested mainly in other research traditions to follow and understand current debates in the quantitative study of war.