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.