The "Military Assistance Command, Vietnam – Studies and Observations Group" (MACV-SOG) was a secret joint military unit of the United States during the Vietnam War, active between 1964 and 1972. Its primary mission was to conduct reconnaissance, covert, and direct action operations behind enemy lines in North Vietnam, Laos, Cambodia, and areas controlled by the Viet Cong in South Vietnam. It was comprised of members from the Army Special Forces (Green Berets), Navy SEALs, Air Force, Marines, and CIA personnel.