Thomas Countryman has been Chairman of the Arms Control Association since 2017. The ACA is a nonpartisan NGO which analyzes key national security issues and advises the executive branch, Congress and the public on choices that promote global security and reduce risk from weapons of mass destruction.
He retired from the Senior Foreign Service in January 2017 after 35 years of service. At that time, he served simultaneously as acting Undersecretary of State for Arms Control and International Security, and as Assistant Secretary for International Security and Nonproliferation, a position he held since September 2011. The ISN Bureau leads the US effort to prevent the spread of nuclear, chemical and biological weapons, their related materials, and their delivery systems.
Previously he served as Principal Deputy Assistant Secretary for Political-Military Affairs (2009-10), and as Deputy Assistant Secretary for European Affairs (2010-11), with responsibility for the Balkans region.
He served overseas at US Embassies in Belgrade, Tunis, Cairo, Rome and Athens; and served in the US at the United Nations, the White House and the Pentagon.