Many have proclaimed the fundamentals of global security were altered by the September 11 terrorist attacks. Do these changes undercut or enhance the role of the United Nations? What do events like the role of the UN in the crisis over Iraq tell us? Here top 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. Their lively presentations of the drama of UN debates establish the contributions and shortcomings of global multilateralism in an era of U.S. hegemony and unilateralism.