Thomas Countryman served as a Foreign Service Officer for 35 years, attaining the rank of Minister-Counselor in the Senior Foreign Service. He most recently served as Acting Under Secretary for Arms Control and International Security until his abrupt removal from the post on January 27, 2017. He has also served as Assistant Secretary for International Security and Nonproliferation, Principal Deputy Assistant Secretary for Political-Military Affairs, Deputy Assistant Secretary for European Affairs, and as the Foreign Policy Advisor to the Commandant of the U.S. Marine Corps. Countryman graduated from Washington University in St. Louis with degrees in economics and political science, and studied at the Kennedy School of Government at Harvard University. He is fluent in Serbo-Croatian, Arabic, Italian, Greek, and German.