United States Army Intelligence and Security Command

Vietnam War

Army Security Agency personnel deployed to Vietnam 4 years in advance of major ground combat elements. The challenge for US advisors, and later for commanders in the field, was to locate an elusive enemy in a hostile environment. Early-on, ASA established short-range direction-finding nets, fielding mobile DF teams using PRD-1s to locate enemy transmitters, and, in turn, enemy forces. The mobile teams were often forced to operate near the enemy. On 22 December 1961, SP4 James T. Davis and nine members of the Army, Republic of Vietnam PRD-1 team he was advising were killed when they were ambushed by Viet Cong. Besides the danger, the ground-based direction-finding mission met with limited success, causing ASA to eventually relegate most of its PRD-1s to supporting intercept operations. As a result, ASA was challenged to develop a new technique (airborne radio direction-finding) to pinpoint the enemy. LEFT BANK was unique among ASA’s airborne radio direction-finding systems in that it was not a fixed-wing aircraft. In 1967 the 509th Radio Research Group (the main ASA unit in Vietnam) erected a memorial at its Saigon headquarters to honor ASA soldiers who made the supreme sacrifice.




AN/PRD-1: Type of equipment used by ASA mobile direction-finding teams. Operating from locations 5-15 miles away from an enemy transmitter, the mobile teams would produce the necessary refined fixes. Once an enemy unit was sufficiently pinpointed, Allied forces could then engage it.


Viet Cong Field Radio

Viet Cong Field Radio: This vacuum-tube voice radio was used by Communist guerrillas. ASA communications intelligence personnel located the enemy by targeting their radio transmissions.


Left Bank Patch

LEFT BANK patch: Worn by ASA members who participated in the helicopter borne direction-finding system. Housed in a UH-1D helicopter, the LEFT BANK system operated in direct support of the local commander.


ASA Soldier

Statue of ASA soldier: A wood carving of a soldier in battle dress carrying an M-16 rifle. The right arm of the soldier points to a separate wooden plaque containing brass plates with the names of ASA personnel killed in action.

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Site Last Reviewed/Cleared/Updated on July 27th, 2012