This 1947 letter from Headquarters Fourth Air Force at Hamilton Field, California, formally attaches 1st Lt. Earle E. Campbell to the Air Reserve Training Detachment following his assignment to the Active Air Reserve. Issued just months before the U.S. Air Force became an independent service branch, the document illustrates the postwar reorganization of American air power and the continued military service of WWII-era airmen within the reserve structure. Project: 218374