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.