Civilian Irregular Defense Group
MACV-SOG was the joint service high command unconventional-warfare task force engaged in highly classified clandestine operations throughout Southeast Asia. It was given the title "Studies & Observation Group" as a cover. The joint staff was allegedly performing an analysis of the lessons learned to that point in the Vietnam War, but it was actually a special operations group with distinct command decision authority
MACV-SOG had five primary responsibilities and the capability to undertake additional special missions as required. Primary responsibilities included: (1) Cross-border operations regularly conducted to disrupt the VC, Khmer Rouge, Pathet Lao and NVA in their own territories; (2) Keeping track of all imprisoned and missing Americans and conducting raids to assist and free them as part of the Escape and Evasion (E & E) mission for all captured U.S. personnel and downed airmen; (3) Training and dispatching agents into North Vietnam to run resistance movement operations; (4) "Black" psychological operations, such as establishing false (notional} NVA broadcasting stations inside North Vietnam; (5) "Gray" psychological operations as typified by the Hue- Phu Bai propaganda transmitter. MACV-SOG was also entrusted with specific tasks such as kidnapping, assassination, insertion of rigged mortar rounds into the enemy ammunition supply system (which were set to explode and destroy their crews upon use) and retrieval of sensitive documents and equipment if lost or captured through enemy action. MACV-SOG was often able to use the intelligence it gathered for its own internal purposes as well as for high command special activities.