I am Professor and Chair of the Political Science Department at The University of Pennsylvania. I write on conflict processes with a focus on civil wars and inter-ethnic conflict in the fields of international relations and comparative politics. Published work in these areas has appeared in the American Political Science Review, International Organization, World Politics, The Journal of Conflict Resolution, Perspectives on Politics, and other journals. I co-authored Making War and Building Peace (Princeton University Press, 2006), the first book to analyze the impact of United Nations peace operations in post-conflict transitions; and Breaking the Conflict Trap: Civil War and Development Policy, one of the first quantitative studies of the causes of civil war around the world. In a two-volume book project (Understanding Civil War: Evidence and Analysis) I developed a nested, mixed-methods research design for the analysis of causes of civil war onset. I currently direct the Penn Identity & Conflict Lab, an inter-disciplinary group working on a broad range of topics related to inter-group conflict. PIC Lab produces cutting-edge research on the causes of inter-group conflict, on civil war and separatism, on the effects of external intervention on ethnic polarization; the stability of power-sharing after ethno-sectarian war; and other mechanisms to reduce or overcome inter-group conflict. We study these questions with attention to the connection between identity politics and conflict processes. Several ongoing projects address conflicts involving immigrants and displaced populations. The Lab is engaged in research on the long-term legacies of violence exposure; the sources of ethnic and national identification; and the effects of integrative institutions in overcoming ethno-sectarian conflict.