What explains war? The so-called bargaining approach has evolved quickly in the past two decades, opening up important new possibilities and raising fundamental challenges to previous conventional thinking about the origins of political violence. Bargaining is intended to explain the causes of conflict on many levels, from interpersonal to international. War is not the product of any of a number of variables creating opportunity or willingness, but instead is caused by whatever factors prevent competitors from negotiating the settlements that result from fighting. Conflict is thus a bargaining failure, a socially inferior outcome, but also a determined choice.

Embraced by a growing number of scholars, the bargaining perspective rapidly created a new consensus in some circles. Bargaining theory is radical in relocating at least some of the causes of conflict away from material, cultural, political, or psychological factors and replacing them with states of knowledge about these same material or ideational factors. Approaching conflict as a bargaining failure—produced by uncertainty and incentives to misrepresent, credible commitment problems, or issue indivisibility—is the “state of the art” in the study of conflict.

At the same time, bargaining theories remain largely untested in any systematic sense: theory has moved far ahead of empirics. The bargaining perspective has been favored largely because of compelling logic rather than empirical validity. Despite the bargaining analogy’s wide-ranging influence (or perhaps because of this influence), scholars have largely failed to subject the key causal mechanisms of bargaining theory to systematic empirical investigation. Further progress for bargaining theory, both among adherents and in the larger research community, depends on empirical tests of both core claims and new theoretical implications of the bargaining approach.

The limited amount of systematic empirical research on bargaining theories of conflict is by no means entirely accident or the product of lethargy on the part of the scholarly community. Tests of theories that involve intangible factors like states of belief or perception are difficult to pursue. How does one measure uncertainty? What does learning look like in the midst of a war? When is indivisibility or commitment a problem, and when can it be resolved through other measures, such as ancillary bargains? The challenge before researchers, however, is to surmount these obstacles. To the degree that progress in science is empirical, bargaining theory needs testing.

As should be clear, the dearth of empirical tests of bargaining approaches to the study of conflict leaves important questions unanswered. Is it true, for example, as bargaining theory suggests, that uncertainty leads to the possibility of war? If so, how much uncertainty is required and in what contexts? Which types of uncertainty are most pernicious (and which are perhaps relatively benign)? Under what circumstances are the effects of uncertainty greatest and where are they least critical? Empirical investigation of the bargaining model can provide essential guidance to theoretical work on conflict by identifying insights that can offer intellectual purchase and by highlighting areas of inquiry that are likely to be empirical dead ends. More broadly, the impact of bargaining theory on the study and practice of international relations rests to a substantial degree on the success of efforts to substantiate the perspective empirically.