Member, Editorial Board, International Organization: 1994–1999, 2001–2006, 2008–2010

Robert L. Powell died on December 13, 2021. Bob was one of the world's foremost applied game theorists and made important contributions to our understanding of the causes of war and to political conflict more generally. Bob pioneered the use of modern non-cooperative game theory (mainly developed in the 1980s) to reconsider and rebuild central arguments of international relations theory. His work consistently sought to go beyond general claims about anarchy and conflict to more clearly identify specific strategic settings, mechanisms, and paths that might lead to organized violence in some cases but not in others. A recurrent theme is the idea that in a surprisingly diverse set of contexts, both interstate and civil conflict are driven by the anticipation of adverse shifts in relative military capability or opportunity, coupled with constraints on the parties’ ability to either regulate or commit not to take advantage of favorable shifts.

Bob's earliest work made groundbreaking contributions to explanations for armed conflict that are based on the parties’ uncertainty about each other's willingness or ability to use force. His first book, Nuclear Deterrence Theory: The Search for Credibility (1990), used innovative methods of incomplete-information game theory to show that what really matters in nuclear crisis bargaining are political judgments about the value of what is at stake, which largely determine how much nuclear risk or damage from limited strikes the states’ leaders are willing to bid. In “Nuclear Brinkmanship, Limited War, and Military Power” (2015), Bob extended this analysis to the interaction between relative conventional capabilities and nuclear risk. A main insight of the book and subsequent IO article is that successful deterrence between nuclear adversaries is fundamentally a political rather than a military problem, and that there is no military or technical way to ensure success, manage escalation, or maneuver the opponent to ensure the preferred outcome in either conventional or nuclear war.

Bob's widely-read second book, In the Shadow of Power: States and Strategies in International Politics (1999), reconsidered three central means by which states have sought security or gain—arming, allying, and threatening to use force. One mechanism he explored was how costly conflict can result from large and rapid shifts in the distribution of power when states exhibit limited ability to commit to future promises. In “War as a Commitment Problem” (2006), his most widely cited article, Bob generalized the underlying mechanism to a remarkably wide range of circumstances in international relations, including conflict related to first-strike or offensive advantages in military technology and conflict related to strategic territory.

Finally, in “Research Bets and Behavioral IR,” his piece in the 2017 IO special issue “The Behavioral Revolution and International Relations,” Bob took a skeptical view, revisiting the limits of rationalist assumptions of behavior and probing the possible limits of the behavioral approach. As in other work, Bob treated assumptions about cognition as “bets” that could generate more or less helpful and empirically supported propositions. Refusing to treat any set of assumptions as inherently better than others, he argued persuasively that scholarly competition would ultimately reveal which assumptions were more useful.