Foreign intervention in ethnic conflicts has received significant attention in the last 20 years. Scholars have initially considered the sources for these interventions through instrumental and affective factors, though a better classification involves grouping these motives between domestic and international factors. The former category assumes that a third state’s internal politics best explain motives of intervention, and that domestic groups within the state have the greatest impact on foreign policy decision making. Theories based on domestic explanations assume that domestic politics greatly matter in the formulation of states’ decisions to intervene or not in ethnic conflicts elsewhere. As for the external explanations, scholars share a common assertion that the international environment is the central determinant explaining third state intervention. These explanations focus on the impact of institutions and international norms on the international relations of ethnic conflicts. In addition to these approaches, this area of research still contains many issues left unaddressed, such as how interference from outside might affect an ethnic conflict, and what forms of analysis might be used to study foreign interventions. Scholars have applied both quantitative and qualitative techniques, and the diaspora literature stands out for relying almost exclusively on case studies and on very notable cases. Otherwise, the rest of the work in this field follows the current standards by using a mixture of case studies and quantitative analyses depending on the questions in play.