This essay covers three broad topics. First, there has been renewed debate about human nature and the roots of intergroup violence and warfare in evolutionary biology, in psychology, and in anthropology. The “ordinary man” hypothesis explains why and how humans justify and participate in violence and atrocities. Second, in addition to interstate wars, political scientists have been studying insurgencies, ethnic cleansing, civil wars, genocide, ethnic riots, and other modes of violence called “new wars.” Based on hundreds of case studies, comparative research and large quantitative data sets, they have theorized about the root causes and dynamics of these conflicts, and about prevention, deterrence, conflict management, and peace making. Third, the social movement and collective action field in sociology developed a mobilization theory for explaining why and how relatively powerless groups confront regimes, how the dynamics of confrontations escalate to civil strife, what outcomes result, and whether violence was necessary for change. All three research traditions contribute insights and findings for conflict theory. In the conclusion, I argue that a theory of conflict should integrate group with state/regime centered analysis (micro with the macro), give more weight to dynamics than to root causes, and make conflict management an equal partner with violent conflict.…