A "Chief of Air Service" was authorized with the rank of major general to replace the previous "Director of Air Service", and an assistant chief created in the rank of brigadier general (from 1920 to 1925 this position was held by Brig. Gen. Billy Mitchell). The primary missions of the Air Service were observation and pursuit aviation, and its tactical squadrons in the United States were controlled by the commanders of nine corps areas and three overseas departments created by the Act, primarily in support of the ground forces. The Chief of the Air Service retained command of training schools, depots, and support activities exempted from corps area control. The headquarters of the Air Service was housed in the Munitions Building in Washington, D.C. and consisted of an executive staff including the chiefs of the Finance and Medical Sections, and four divisions, each administered by a chief: Personnel Group, Information Group (Intelligence), Training and War Plans Group, and Supply Group.