Sarah Sewall teaches international affairs at the Harvard Kennedy School of Government, where she also directs the Program on National Security and Human Rights. Dr. Sewall is the founder and faculty director of the Mass Atrocity Response Operations (MARO) Project. She is currently leading a study on civilian casualties with the United States Military. She led the Obama Transitions National Security Agency Review process in 2008. During the Clinton Administration, Dr. Sewall served as the first Deputy Assistant Secretary of Defense for Peacekeeping and Humanitarian Assistance. From 1983-1996, she served as Senior Foreign Policy Advisor to Senate Majority Leader George J. Mitchell on the Democratic Policy Committee and the Senate Arms Control Observer Group. Before joining Harvard, Dr. Sewall was at the American Academy of Arts and Sciences where she edited The United States and the International Criminal Court (2002). Her more recent publications include the introduction to the University of Chicago Edition of the U.S. Army and Marine Corps Counterinsurgency Manual (2007) and, with John White, Parameters of Partnership: U.S. Civil-Military Relations in the 21st Century (2009). She is a member of the U.S. Department of Defense's Defense Policy Board Advisory Committee and the Center for Naval Analyses Defense Advisory Committee and is on the board of Oxfam America. She graduated from Harvard College and received her doctorate from Oxford University, where she was a Rhodes Scholar.

In 2007, Sewall founded the MARO Project to create a military concept of operations for intervening to halt mass atrocity.