As peace operations become the primary mechanism of conflict management used by the UN and regional organizations, understanding their problems and potential is essential for a more secure world. In this revised and updated second edition, Paul Diehl and Alexandru Balas provide a cutting-edge analysis of the central issues surrounding the development, operation, and effectiveness of peace operations. Among many features, the book: Traces the historical development of peace operations from their origins in the early 20th century through the development of modern peacebuilding missions and multiple simultaneous peace operations. Tracks changes over time in the size, mission and organization of peace operations. Analyses different organizational, financial, and troop provisions for peace operations, as well as assessing alternatives. Lays out criteria for evaluating peace operations and details the conditions under which such operations are successful. Drawing on a wide range of examples from those between Israel and her neighbours to more recent operations in Bosnia, Somalia, Darfur, East Timor, and the Congo, this new edition brings together the body of scholarly research on peace operations to address those concerns. It will be an indispensable guide for students, practitioners and general readers wanting to broaden their knowledge of the possibilities and limits of peace operations today.