What Do We Know about War? reviews the causes of war and the conditions of peace. Drawing analyses from the thirty-five year history of this discipline, leading researchers explore the roles played by alliances, territory, arms races, interstate rivalries, capability, and crisis bargaining in increasing the probability of war. They emphasize international norms and the recent finding that democratic states do not fight each other as factors that promote peace. This book offers an accessible and up-to-date overview of current knowledge and an agenda for future research.