Established in December 1949, the Air Defense Command 28th Air Division assumed responsibility for conducting the air defense of an area that embraced California, Utah, Nevada, Colorado, and Arizona. It became part of the Western Air Defense Force in 1950. With no fighter interceptor squadrons directly assigned, the division used interceptors of the 78th Fighter Wing, based at Hamilton Air Force Base, California, as well as Air National Guard interceptors based within its geographical area.