The United Nations is among the most important international organizations. But is it only a talking shop? Or does it have a role, as forum, vehicle, or actor, in addressing the most important security issues facing the world today? Here top international scholars examine the role of the UN in preventing international and civil violence, arms control, deterring and reversing aggression, and addressing humanitarian crises. The chapters are concise while providing depth of understanding of the issues, positions, and problems facing the United Nations and its member states in grappling with increased opportunities and threats.