 In 1998 he joined the faculty of the Edmund A. Walsh School of Foreign Service at Georgetown University, becoming Director of Georgetown's Center for Peace and Security Studies in 2000.In 2005, he was appointed Dean of the Elliott School of International Affairs and Professor of International Affairs and Political Science at the George Washington University.He held that position until 2015, after which he continued at the school, as a faculty member with a research focus on international security.