History of the United States Air Force Office of Special Investigations in Vietnam 1962 - 1975

The Air Force Office of Special Investigations (OSI) officially began its operations in Southeast Asia when Special Order G-92, Hq PACAF, dated 7 Dec 1961 activated OSI Detachment 2 at Tan Son Nhut Airfield, South Vietnam, and OSI Detachment 3 at Don Muang Air Base, Thailand. Both detachments fell within the purview of District 42 headquartered in the Philippines. OSI first staffed these two detachments with TDY personnel in January 1962. Effective 1 March 1962, OSI District 50 was organized and activated at Tan Son Nhut Air Field. Permanent party OSI personnel started arriving in March 1962. Authority for this organizational change was set forth in Special Order G-19, Hq, PACAF, dated 27 February 1962. This new District Office and its new subordinate detachment office (Detachment 5001) at Don Muang Air Base supplanted the two detachment offices that had been functioning under District 42. With this change, OSI instituted the first organized, locally-directed and permanently-established USAF counterintelligence effort and criminal investigative mission in Southeast Asia. Eventually OSI District 50 would oversee the operations of OSI units at the 10 major air bases in Vietnam. OSI staffing would reach the level of approximately 100, special agents, administrative, and interpreter/translator personnel. OSI District 50 and Detachment 5003 at Da Nang were the last two units when both closed in March 1973 with the District deactivated on 27 March 1973. The last four Special Agents assigned to District 50 departed Tan Son Nhut on 28 March 1973. Following that date, OSI support to operations in Vietnam was provided on a temporary duty basis out of District 51, Thailand.

March 2023 marked the 50^th anniversary of the heroic activities of OSI personnel in this war zone. This history attempts to describe the units and missions of District 50, salutes the more than 570 OSI Special Agents (SA) and their supporting interpreters and administrative/logistic personnel who served in Vietnam. (Writers note: the writers were able to identify over 570 personnel who served with OSI in Vietnam and estimate that there are at least 200 more yet to be identified.) This history captures some of their investigative activities and collections efforts in support of the security of United States Air Force (USAF) assets in Vietnam and Southeast Asia (SEA).