His specialty is international relations and comparative politics, with a regional focus on the former Yugoslavia and Russia. He is the author of the book The Myth of Ethnic War: Serbia and Croatia in the 1990s, which won the American Political Science Association's Prize for the Best Book on European Politics and Society as well as the Best First Book Award of the Council for European Studies. He has also published numerous scholarly articles on topics related to the Yugoslav wars, nationalism, ethnic conflict, and multiculturalism in the Balkans in journals such as International Security, Foreign Affairs, Nationalities Papers and Journal of Democracy.