The Defense Clandestine Service (DCS) is an arm of the Defense Intelligence Agency (DIA), which conducts clandestine espionage, intelligence gathering activities and classified operations around the world to provide insights and answer national-level defense objectives for senior U.S. policymakers and American military leaders. Staffed by civilian and military personnel, DCS is part of DIA's Directorate of Operations and works in conjunction with the Central Intelligence Agency's Directorate of Operations and the U.S. military's Joint Special Operations Command. DCS consists of about 500 clandestine operatives, which is roughly how many case officers the CIA maintained in the early 2000s prior to its expansion.

The Defense Intelligence Agency (DIA) is an intelligence agency and combat support agency of the United States Department of Defense, specializing in defense and military intelligence.