Historically, civil wars ended in one-sided victory. With the end of the Cold War, however, the very nature of how civil wars end shifted: wars became two times more likely to terminate in negotiated settlement than in victory. Since the terrorist attacks of September 11, 2001, the proportion of victories has increased, especially for civil wars that include a terrorist group; wars are also ending less frequently. Why would civil war termination vary by time period? The literature on civil wars looks to three basic types of causes: domesticstructural factors, bargaining dynamics, and types of international intervention. Current explanations cannot account for why civil wars would end differently in different time periods because, as Kenneth Waltz might say, they are “reductionist” in nature. Material and ideational factors constitute the international political environment, which varies in different time periods. This environment drives outside actors' normative strategies of viewing victory, negotiation, or stabilization as the appropriate solution to civil war. These norms, in turn, directly affect how civil wars end. A novel, three-part methodological approach using quantitative analysis, case studies, and original content analysis demonstrates that civil wars tend to end the way external actors think they ought to end.