ADC was inactivated on 1 October 1979, with its "atmospheric" resources e.g., its Regular Air Force and Air National Guard F-101, F-102 and F-106 fighter-interceptors; ground-based warning radars; and associated bases and personnel) subsequently transferred to TAC under a sub-entity named Air Defense, Tactical Air Command (ADTAC). ADC's EC-121 Warning Star airborne early warning aircraft had already been retired by 1978 and it never received that aircraft's replacement, the E-3 Sentry AWACS, that began entering the TAC inventory in 1977. As a result of changes in USAF doctrine and tactics, AWACS was always intended as strictly a TAC airframe nominally operating from forward-deployed locations and incorporating many of the lessons learned from employing the EC-121 in its Big Eye, College Eye, Rivet Top and Disco roles with PACAF's 7th Air Force during the Vietnam War.