Air Defense Command The War Department established an Air Defense Command on February 26, 1940. This command, operating under the control of the First Army Commander from March 2, 1940, to September 9, 1941, engaged in planning for air defense. Before the United States entered World War II, air defense was divided among the four air districts later, First, Second, Third, and Fourth Air Forces based in the United States. In mid-1944, when the threat of air attack seemed negligible, this air defense organization was disbanded. Subsequently, no real air defense organization existed until the second Air (later Aerospace) Defense Command was established in 1946 as a major command of the Army Air Forces (AAF). The Aerospace Defense Command declined after the Air National Guard and Air Force Reserve gradually assumed more and more of the air defense mission. In 1980 Air Defense Command resources were divided between Tactical Air Command and Strategic Air Command. Some functions of the command passed to the Aerospace Defense Center, a direct reporting unit that inactivated on October 1, 1986. Lineage Established as Air Defense Command on March 21, 1946. Activated as a major command on March 27, 1946. Became a subordinate operational command of Continental Air Command on December 1, 1948. Discontinued on July 1, 1950. Reestablished as a major command, and organized, on January 1, 1951. Redesignated Aerospace Defense Command on January 15, 1968. Inactivated on March 31, 1980.