officers and enlisted men at the field. Because there were so few personnel on hand, morale was low and workloads were strenuous for the installation throughout the early Cold War period. On 21 March 1946, Strategic Air Command (SAC) was activated and on 31 March 1946, SAC's Fifteenth Air Force assumed operation of Kirtland Field. The 58th Bombardment Wing remained in command of the installation under SAC, and there was a return of personnel. Shortly thereafter, an "S-2 Section" was established on base and became responsible for the security of Kirtland Field and the "W-47 Project". The W-47 Project had been the wartime operation established at Wendover Army Air Base to train the 509th Composite Group to drop the atomic bombs on Hiroshima and Nagasaki. In keeping with Kirtland Field's mission to assist Sandia Base's Z Division with the marriage of bombs and aircraft, the 509th Composite Group's Flight Test Section was transferred to Kirtland. As these arrangements were taking place, a new subgroup of the Manhattan Project at Los Alamos was being organized. Titled the Z Division for its chief, Dr. Jerrold Zacharias, a Los Alamos scientist from the Massachusetts Institute of Technology (MIT), the new group's mission was to manage the engineering design, production, assembly, and field-testing of the non-nuclear components associated with nuclear bombs. Construction began on guard, storage, administrative, and laboratory facilities for the Z Division. Because the airfield was still receiving surplus warplanes, the U.S. Army constructed a fenced area for classified activities. They employed security measures including tanks, guard towers, and watch dogs to protect the small stockpile of atomic weapons parts. In the years after the war, Sandia Base boundaries would vastly expand to include the thousands of acres owned by the NMPG, which occupied much of the East Mesa. Base operations began to increase in June 1946 with the organization of a full-scale Ground Training Program and the arrival of the Special Ordnance Squadron and Special Transport Flight of the 58th Bombardment Wing. Aircraft being maintained by the 58th Bombardment Wing included five B-29 Superfortresses and C-45 Expeditors, two C-47s, B-25 Mitchells and L-5s, and a C-46 Commando, AT-11 Kansan, F-80 Shooting Star, F-61 Black Widow, and F-59 Airacomet. Prior to the new Ground Training Program, which began officially on 24 June 1946, some training was carried out by individual units, primarily physical engineering, bombardiering, and armament. With the new program came