In Vietnam ASA operations were rigidly protected by operational segregation, strictly enforced operational procedures, and special classification techniques called special access and codeword protection of all communication intelligence practices and products.
The ASA also renamed their combat support units calling them instead "Radio Research Units" or RRU. It was a shallow cover intended to avoid compromise and dedicated targeting of ASA assets by the enemy.
Accordingly the ASA assigned Radio Research Detachments (about 70 men) to separate brigades like the 173rd Airborne Brigade and the 5th Special Forces Group; Radio Research Companies (about 200 to 500 men) were assigned to divisions; Radio Research Battalions (comprised of several companies and detachments) were assigned to corps; and the 509th Radio Research Group assigned to MACV.
ASA Field Stations provided additional support using fabricated facilities with permanent antenna fields located in Vietnam and elsewhere. The detachments, companies, including aviation companies, and battalions provided support directly to combat units. Field stations and some aviation units provided general area support regionally and across all of Vietnam. All Radio Research units provided operational support to one another when needed.
Radio Research units served side by side with the brigades and divisions to whom they were attached. The special orders written to define the relationship between supporting ASA units and a supported combat unit usually required the supported unit, say the 4th Infantry Division, to provide logistics (ammunition, rations, water, fuel, mail, common repair parts, and maintenance, as some examples) to the supporting 374th Radio Research Company. The parent Radio Research Battalion (the 313th in this case and assigned to II Corps) provided personnel administration to include assignment, promotions, rest and recuperation (R&R), military justice, and major logistical support (weapons, trucks, and ASA peculiar equipment, as examples).