A large literature has demonstrated that international action can promote the resolution of civil wars. However, international actors do not wait until violence starts to seek to manage conflicts. This article considers the ways in which the United Nations Security Council (UNSC) reduces the propensity for self-determination movements to escalate to civil war, through actions that directly pertain to the disputing actors or that indirectly shape actor incentives. It examines the relationship between the content of UNSC resolutions in all self-determination disputes from 1960 to 2005 and the onset of armed conflict in the disputes. The study finds that diplomatic actions that directly address disputes reduce the likelihood of armed conflict, and that military force and sanctions have more indirect preventive effects.Over the last several decades, international actorsoften working through international organizations such as the United Nations (UN)have focused increasing attention on managing violent intrastate conflict. This trend accelerated after the end of the Cold War, as efforts at the UN and other international bodies were then not stymied by superpower competition. Former UN Secretary-General Boutros-Ghali's Agenda for Peace (1992) emphasizes four areas of action that the international community could and should undertake to promote peace: preventive diplomacy, peacemaking, peacekeeping and post-conflict peace building. A large body of literature has examined the effect of the latter three types of action, and many of the conclusions reached have been optimistic. Studies have concluded that the UN can be effective at building peace, 1 that peacekeeping works, 2 that mediation can help facilitate settlement 3 and that legal dispute resolution is especially effective. 4 While this literature has advanced academic understanding of the effect of international actions and has had implications for policy makers seeking to resolve violent conflicts, there is still a substantial gap in our understanding of international efforts to prevent violent intrastate conflicts. Virtually all existing work focuses on managing or resolving ongoing violent conflicts.