Scholars generally have ignored the difficulty of convincing states to cooperate when advocating particular methods to address ethnic conflicts. Instead, they assume that states want to end the conflict in question, and then propose various solutions that largely depend on international cooperation. I consider the importance of international support for conflict prevention, the use of force, security guarantees, and partition. The success of each of these strategies crucially depends on what outside actors do, revealing the need for scholars to consider why states behave toward ethnic conflicts as they do. I then address three sets of explanations of the international relations of ethnic conflict: the possible impact of norms, realist explanations, and arguments focused on domestic politics. “Domestic” refers to two sets of approaches that focus on the interests of leaders: ethnic politics and casualty aversion. States may disagree about which norms (self determination vs. territorial integrity) to apply and take opposite sides. Realist arguments suggest that cooperation will be difficult as states may take conflicting sides. Ethnic politics suggests that states take sides based on the ethnic identities of the actors in the conflict and their ties to outsiders. Casualty aversion considers the limits placed on intervention since leaders desire not to risk the lives of the soldiers. I conclude by considering strategies for managing ethnic conflict that take into account the difficulties of cooperation: minilateralism, subcontracting, and the strategic manipulation of identity.