An understanding of why states fight wars requires an understanding of why they end wars. These phenomena form interrelated parts of a larger process of interstate bargaining. Yet, compared to the research on the outbreak of wars, there has been much less attention paid to their termination. These conflicts end when the belligerents reach convergent expectations that they have more to gain or less to lose if they stop fighting than if they continue to do so. This article presents several factors hypothesized to hasten or delay this mutual recognition and, therefore, to shorten or prolong a conflict. Boolean algebra is applied to study the individual and joint effects of these factors on the duration of 23 interstate wars during 1945-92. The results show that short wars stem from different causal combinations, therefore suggesting the inadequacy of any monocausal explanation. Moreover, this analysis points to the importance of context-specific understanding because the same factors can have different effects on shortening war and different factors can have similar effects on this outcome under different circumstances. Contrary to the argument in favor of an incremental escalation of military pressure on an adversary, massive and intense fighting at the outset of a war has been nearly a necessary though insufficient condition for a quick ceasefire. This conclusion supports the view that private information inclines states to fight wars but the revelation of this information in the subsequent fighting puts them in a better position to reach a settlement.