Intelligence Force had role in Vietnam conflict

By Lori TaggMarch 6, 2015

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Fort Huachuca, Arizona - Prior to the commitment of U.S. combat troops to the conflict in Vietnam in 1965, the Military Assistance Command--Vietnam, MACV, received intelligence support from two Army Intelligence detachments.

The 46-man, 704th Intelligence Corps Detachment had been activated in 1962 to provide counterintelligence, CI, support, to include counterespionage, countersabotage and countersubversion. The other unit, Detachment I of the 500th Intelligence Corps Group, had 56 officers and enlisted men advising and assisting the South Vietnamese with collection requirements in the field.

In addition, the U.S. Army Security Agency's (ASA's) 3rd Radio Research (RR) Unit had been in Vietnam since 1961 providing Signals Intelligence, SIGINT, support with both aerial and ground-based assets. Finally, approximately 200 officers were serving as intelligence advisors to the South Vietnamese military.

By the summer of 1965, as the number of U.S. military personnel in Vietnam grew, MACV J2 Maj. Gen. Joseph McChristian recognized that his small pool of intelligence personnel would not be able to manage the expected growth in intelligence requirements. He immediately requested the deployment of an MI group from Fort Bragg, North Carolina, to South Vietnam to control an expanding range of intelligence assets.

Within two years, McChristian expanded his J2 by nearly 3,000 intelligence Soldiers to plan, direct and conduct general non-cryptologic intelligence operations in Vietnam. The first unit to arrive, in late November 1965, was the 525th MI Group.

The 525th was headquartered on Tan Son Nhut Air Base in Saigon and worked directly under the J2's operational control. The group supplied the command and control headquarters for several other MI units that arrived over the next year.

The 525th MI Group remained in Vietnam until March 1973. Over the course of its seven and a half years in Vietnam, the group earned 16 campaign streamers and four Meritorious Unit Commendations. Individual detachments and companies earned many more.

More than 1,000 personnel of the 519th MI Battalion also began arriving in Vietnam in late 1965. After receiving specialized training, these officers and enlisted men were assigned to man the four multi-national intelligence centers in Saigon: the Combined Document Exploitation Center, Combined Materiel Exploitation Center, Combined Military Interrogation Center, and the Combined Intelligence Center.

South Vietnamese and American intelligence personnel worked side-by-side to mitigate limitations. The U.S. Army provided trained and experienced personnel as well as equipment and other resources; the South Vietnamese provided knowledge of the enemy's language and culture. The 519th MI Battalion continued to man the four combined centers until October 1972.

Following the 519th, the 1st MI Battalion (Aerial Reconnaissance Support [MIBARS]) arrived in Saigon in December 1965 to oversee the Army's aerial reconnaissance assets. Personnel from the MIBARS also interpreted, reproduced and delivered Air Force imagery to Army units. Five detachments operated in the corps tactical zones throughout the country.

In addition, MIBARS Tactical Air Reconnaissance liaison officers served as the link between the field commanders and the Air Force or Marine reconnaissance units that flew the reconnaissance missions. The 1st MIBARS remained in Vietnam until April 1972.

In the fall of 1966, the final two major intelligence units, both theater-level MI groups, arrived in Vietnam. The 135th MI Group absorbed the mission of the 704th Intelligence Corps Detachment and continued to provide CI support. Teams were sent into six regions throughout South Vietnam. Most were co-located with the Vietnamese Military Security Service. The 149th MI Group absorbed the mission of the 500th's Detachment I and oversaw Human Intelligence, HUMINT, collection in the field.

Later in the war, the unique situation of having two MI groups subordinate to another group was remedied when the 135th and 149th MI Groups were inactivated. The 525th absorbed the assets of the two former groups and divided operations among six provisional battalions stationed throughout South Vietnam: the 1st in Da Nang, 2nd in Nha Trang, 3rd in Bien Hoa, 4th in Can Tho, 5th in Saigon, and 6th in Tan Son Nhut. Each of these battalions performed counterintelligence, collection and direct support functions for tactical elements in their respective corps tactical zones.

In addition to these four major subordinate units, the 525th MI Group controlled several more intelligence teams and detachments during the course of the war. Tactical forces in Vietnam had a better intelligence system than at any previous time in the Army's history. Each division had an organic company-sized MI detachment which augmented the division G2 staff with counterintelligence, order of battle, imagery interpretation and interrogation sections.

At the brigade level, smaller MI detachments supported the S2s. South Vietnamese intelligence detachments complemented both division and brigade MI detachments, supplying critical linguistic expertise.

By 1967, more than 600 American advisors were supplementing the intelligence activities of the 525th MI Group. Working with their South Vietnamese counterparts through a network of district intelligence and operations coordinating centers in the countryside, they were a source of tactical military intelligence and increasingly became involved in uncovering the Viet Cong infrastructure that supported the insurgency.

Additional ground intelligence was provided by the teams of the 5th Special Forces Group, 1st Special Forces and the Vietnamese Civilian Irregular Defense Groups they advised. Special Forces personnel conducted intelligence and counterintelligence operations through their contacts with the local Montagnard tribesmen and served as the Army component of the MACV Studies and Observation Group, which collected intelligence and carried out special operations in denied areas.

Finally, for SIGINT support, the ASA deployed about one-fifth of its 30,000-man total strength to Southeast Asia. The 3rd RR Unit that had arrived in 1961 was replaced by the 509th RR Group in June 1966. The 509th commanded two ASA battalions, each attached to an Army field force (the 303rd at Long Binh and the 313th at Nha Trang); the 224th Aviation Battalion; and a fixed field station at Phu Bai.

To provide direct support to tactical units, the ASA attached more than 20 specially tailored companies and detachments to American divisions and brigades, such as the 404th ASA Detachment to the 173rd Airborne Brigade or Company B, 313th ASA Battalion to the 1st Infantry Division. These direct support units had a secondary mission to support the theater and national communications intelligence efforts. The 509th RR Group remained in Vietnam until March 1973. For its seven years of commitment to the war in Vietnam, the group received three Meritorious Unit Commendations and two awards of the Republic of Vietnam Cross of Gallantry with Palm.