My research focuses primarily on the causes of interstate war, foreign policy decision-making, political psychology, and qualitative methodology. I have published articles and/or books on the historical evolution of warfare; the dynamics of power relationships, including theories of balance of power, power transition, and preventive war; domestic politics and war, including diversionary theory, political oppositions, and audience costs; the political economy of war and peace, including the militarization of commercial rivalries and the relationship between economic interdependence and international conflict; the psychology of decision-making, including prospect theory and time horizons; qualitative methodology, including case studies and counterfactual historical analysis; and the First World War. Here I briefly summarize my current research and outline some future projects I hope to pursue. I then go back and describe some of my earlier work that provides the context and foundation for my current and future research. Please see my CV for the titles of works cited here and for a more complete list of my publications.  

Current Projects and Future Plans

My collaborative book project with William R. Thompson on balance of power theory, tentatively titled “Hegemonic Threats, Balancing, and War: Five Centuries of Theory and Evidence,” has occupied most of my recent attention. Building on my earlier solo and collaborative work on the topic (2003, 2004, 2005, 2010), Thompson and I argue that great powers have systematically balanced against hegemonic threats in the modern European system but not in the global maritime system. We test this argument empirically through a statistical analysis spanning the last five centuries, adding to our earlier work by incorporating strategic rivalries, exploring the relationship between war and balancing, and updating our data. Our argument that the modern European system is historically distinctive raises the question of why balancing has always worked to block the emergence of hegemony in European system during the last millennium but less frequently in other autonomous continental systems (e.g, the Warring States period in ancient China). We offer a provisional explanation and illustrate it with a qualitative historical study of non-Western systems spanning several millennia.

I have recently begun a project with co-author Yingtong Chen on the question of Who Takes Risks, When, Where, and Why? Risk is a central concept in international relations theories, but most theories focus more on the consequences of risk preferences rather than on the sources of risk taking. In this review essay we survey the distinctive literatures on risk perception and risk preferences in economics, psychology, sociology, organizational theory, management science, and other disciplines. We demonstrate that different disciplines emphasize different and incompatible conceptions of risk, and that there is a frequent failure to specify the causal mechanisms through which risk perceptions and risk propensity influence behavior.

In another project Norrin Ripsman and I build on our earlier research on the appeasement of Nazi Germany and focus on British military intelligence on German capabilities in the 1930s. Our theoretical question is the extent to which Prime Minister Neville Chamberlain and his allies politicized British intelligence to support their preferred strategy of appeasement. Evidence of politicization would undermine our earlier “buying time” interpretation of British appeasement, but our investigation of archival and secondary sources yields no evidence of top-down politicization. Another current project is an essay on power transition theory and the outbreak of World War I, for historian William Mulligan’s “Companion Volume on the Origins of the First World War.”

As for future projects, I am long overdue on a contract with Routledge for a book of my most influential article-length studies on war, tentatively titled “Analyzing the Causes of War: Power, Politics, and Psychology.” In addition, after four decades of teaching a graduate seminar on Theories of War and Peace, I want to integrate materials from that course, and from my many review essays published over the years, into a book.

At some point, I want to get back to my long-term research program on great power wars in the last five centuries of the modern Western system. I am continuing to revise the war data from my 1983 book, with particular attention to (1) refinements in the dates of entry into and departure from the great power system for each of the great powers; (2) the more precise identification of the initiation and termination dates of each of the 55-60 great power wars since 1495 (specified to the day rather than the year); and (3) the question of whether simultaneous or temporally proximate wars should be disaggregated into separate wars. I hope to publish the revised data set as an article.

In the process of refining my quantitative data, I have constructed detailed historical timelines of each great power war since 1495. These timelines are far more detailed than those available in any encyclopedia of war or of world history. I have also begun to construct a set of interpretive essays on the causes of each of the great power wars in the modern system, aiming for a multi-volume study of all great power wars since 1495. Before I finish that project, however, I may focus more narrowly on a particular subset of those wars, the ten or so hegemonic (systemic/general) wars in the last five centuries. This would be the basis for a comparative study of the causes of hegemonic wars.

I have also been thinking of expanding my 2015 article on counterfactual analysis in historical case studies into a book length treatment, with more detailed applications to the First World War and other cases.

Earlier Projects

Historical Evolution of War

My work on the historical evolution of war centers around my 1983 book, War in the Modern Great Power System, 1495-1975, along with a 1982 article and a 2001 study with Thomas Walker and Martin Edwards. The book describes my data set on great power war over the last five centuries of the modern great power system, provides descriptive statistics, and explains the declining frequency but rising severity of great power warfare. I also worked with T. Clifton Morgan on war contagion (1986) and on the relationship between the frequency and seriousness of war (1984). In The Arc of War: Origins, Evolution, Transformation (2011), William Thompson and I extend the analysis of the evolution of war back eight millennia. We emphasize the coevolution of war, threat perception, political economy, military and political organization, and weaponry from early tribal systems to the contemporary period. I joined in debates with Steven Pinker, Joshua Goldstein, and others on the hypothesized decline of interstate war and how to explain it (2013).

Dynamics of Power Relationships

My ongoing research on theories of balance of power, power transition, and preventive war grow out of my long-standing interest in the dynamics of power in international relations. After my earlier work on alliances (1981), the offense/defense balance (1984), polarity (1985), and hegemonic war (1985), I embarked on a reconceptualization of balance of power theory. This led to two articles (2005, 2010) and a journal correspondence (2011) on the topic and now to the book project described above.

Balance of power theory is often contrasted with power transition theory. I have highlighted some limitations of power transition theory in my work with Jonathan DiCicco (1999, 2003) and applied the theory to the rise of China (2008). Andrew Greve and I then broadened the theory’s central but under-theorized variable of (dis)satisfaction to include status dissatisfaction, and applied the concept to the Sino-Japanese power transition leading to the Sino-Japanese War of 1894-95 (2018).

One possible mechanism leading to war during power transitions involves a preventive war by the declining power. In my long-standing research program on preventive war, I clarify the meaning of the concept and specify the conditions under which states are most likely to adopt preventive war strategies (1987, 2008, 2011). I also conduct several historical studies to illustrate different theoretical propositions relating to preventive war. Arguing that Israel was driven by preventive logic in the 1956 Suez/Sinai War, Joseph Gochal and I question the argument that democracies do not fight preventive wars (2001/02). In a 2014 piece, I distinguish between revisionist and status quo preventive war strategies and explore the interaction between prevention and preemption in a study of German strategy in 1914. Norrin Ripsman and I examine the mysterious case of why a rapidly rising Germany did not precipitate a preventive war in the 1930s (2007, 2012). We argue that British expectations that the distribution of power would shift in their favor by the late 1930s led them to adopt a “buying time” strategy of appeasement, which we contrast with standard conceptualizations of appeasement (2008). Whereas most of the literature on preventive war looks at the perceptions and calculations of the preventer, William Mulligan and I examine the perceptions and behavior of the target, with an historical study of Russia in 1914 (2017). Eventually, I plan to integrate all of this work into a book-length treatment of preventive war.

Domestic Politics and War

My work on domestic politics and war began with a 1988 review essay, studies of the diversionary theory of war (1989, 1992 with Lily Vakili), and analyses of the domestic sources of alliances and alignments with Michael Barnett (1991, 1992). One neglected implication of diversionary theory is that political oppositions, anticipating that a successful war would benefit the party in power, might adopt the politically risky strategy of opposing war. William Mabe and I explored the motivations and constraints underlying the phenomenon of politically-motivated opposition to war (2004), which I developed into a formal model with Patrick Shea and Terrence Teo (2014). This pattern has important implications for signaling theories, and suggests that in the absence of additional information the domestic opposition’s behavior does not necessarily send an unambiguous signal of the government’s intentions.

An alternative domestic political theory of signaling emphasizes “audience costs,” defined as the domestic costs a leader pays for making a foreign threat and then not following through. After my earlier conceptual contribution (2012), Michael McKoy, Paul Poast, Geoffrey Wallace, and I (2015) undertook an experimental study of audience costs. We argued that if scholars are correct that audience costs are driven by public concerns about the international implications of an inconsistency between a leader’s statements and actions, then publics should also punish leaders for “backing in” to a conflict after first promising they would stay out. Our experimental study confirmed this hypothesis but demonstrated that punishment is higher for backing out than for backing into a conflict. Jayme Schlesinger and I, in an historical study of British behavior in the 1863-64 Schleswig-Holstein crisis (2021), demonstrate that multiple internal elite audiences can send signals to foreign actors, confounding the effects of standard audience costs mechanisms. We also argue that the assumptions underlying formal models and experimental scenarios of audience costs fail to adequately capture the complexity of the politics of signaling.

The Political Economy of War and Peace

My work on the political economy of war and peace includes studies of both the militarization of commercial rivalry and the relationship between economic interdependence and international conflict. The project on the militarization of commercial rivalries was motivated by the rivalry literature’s neglect of both the commercial roots and domestic sources of many strategic rivalries. Focusing on the 17th century Anglo-Dutch rivalry (1998, 1999) and the 18th century Anglo-Spanish rivalry (2011), my coauthors and I demonstrate that standard interpretations of the wars associated with each as “pure trade wars” are misguided, and that in each case domestic politics played a critical role in the escalation of a commercial rivalry to war.

Whereas most studies of economic interdependence, war, and peace examine the impact of trade on conflict, Katherine Barbieri and I analyze the impact of war on trade. Contrary to the implications of standard liberal and realist theories that trade between wartime adversaries will stop or at least significantly decline with the outbreak of hostilities or before, our interrupted time series and historical case study analyses demonstrated that trading with the enemy often continues during wartime (1999, 2001, 2004). I recently returned to the question of the impact of economic interdependence on conflict. In a study of the four decade period leading to the First World War, William Mulligan and I broaden the concept of interdependence to include social and cultural as well as economic dimensions. We demonstrate that historically unprecedented levels of interdependence helped shape power politics in both cooperative and conflictual directions (2019). In another paper Mulligan and I identify several system-level mechanisms leading from economic interdependence to war that have been neglected a literature focused primarily on dyadic relationships. We apply our hypotheses to the First World War and other cases (2023).

The Psychology of Judgment and Decision-Making

My work on the psychology of judgment and decision-making in foreign policy includes studies of misperception (1983), learning (1994), prospect-theoretic concepts of loss aversion and risk propensity (1992, 1997, 2000, 2003), time horizons (2007), and threat perception and intelligence failure (2009 with Uri Bar-Joseph). With Philip Streich I explore the nature of informational problems in the Russo-Japanese crisis leading to the war of 1904-05, and in the process suggest behavioral modifications to the influential bargaining model of war (2016). I have also written several broader review essays on the political psychology of foreign policy decision-making, for the first, second, and third editions of the Oxford Handbook of Political Psychology (2003, 2013, 2023). I served as co-editor of the second and third editions.

Qualitative Methodology

I have written some review essays on case study methodology (2002, 2007, 2008), the last of which is now my most widely cited publication. I have also written a couple of essays on the differences, similarities, and synergies of diplomatic history and international relations theory (1997, 2001). My collaboration with Gary Goertz on a co-edited book on necessary condition counterfactuals (2008) got me thinking more about concepts of causation. I wrote one piece on the “path to war” concept (2012), and hope to get back to the undertheorized concept of causal pathways before too long. I also wrote two papers on the role of counterfactual analysis in causal inference in case study research (2008, 2015). My fundamental question is whether and to what extent did something that did not happen but that might have happened and maybe should have happened help us understand what actually did happen. At some point I hope to write a book-length study of counterfactual analysis in historical research on war and peace.

The First World War

In addition to using the First World War to illustrate a variety of theoretical models and mechanisms, I have undertaken some studies with the more idiographic aim of constructing and testing new explanations of the war itself. Developing a “soft” game-theoretic framework in my initial study of the First World War (1990-91, 1991), I identified four distinct outcomes of the July 1914 crisis: peaceful settlement, local war in the Balkans, continental war, and world war. I specified the leading actors’ preferences over these outcomes and used this framework to guide a detailed case study of the crisis. For the centenary of the First World War John Vasquez and I edited a volume on the outbreak of the war that included both political scientists and historians (2014). The volume included my own study of the role of preventive logic in German decision-making in 1914. In a formal correspondence with Jack Snyder (2015), I questioned his argument that most great powers perceived 1914 as the optimal time for war. William Mulligan and I (2017) addressed the puzzle of why Russia was so confrontational in 1914 when its relative strength would have been much greater three years later. Mulligan and I also published a comparative study of the July 1914 crisis and the great power crises during the Balkan Wars (2021). The study was motivated by the fact that many of the key structural conditions, cultural attitudes, and individual leaders commonly invoked to explain the outbreak of the First World War were present in the earlier crises. Our aim was to explain why the July Crisis, but not the earlier crises, escalated to a great power war, and to emphasize the importance of comparative longitudinal studies.