Groves had chaired the committee responsible for target selection, and by the end of May 1945 the list had been narrowed to Kokura, Hiroshima, Niigata, and Kyōto, all cities that had not yet been subjected to Gen. Curtis LeMay’s strategic bombing campaign. Kyōto, Japan’s ancient capital, was consistently placed at the top of the list, but Stimson appealed directly to Truman to remove it from consideration because of its cultural importance. Nagasaki was added in its place. Hiroshima became the primary target because of its military value—the city served as the headquarters of the Japanese Second Army—and because planners believed that the compactness of the urban centre would most vividly demonstrate the destructive power of the bomb.
The pilots, mechanics, and crews of the 509th Composite Group of the Twentieth Air Force had all trained with the specially modified B-29s that would serve as delivery vehicles for the bombs. Col. Paul W. Tibbets, Jr., the commander of the 509th, would pilot the B-29 that would drop the first bomb. His 11-man crew included Maj. Thomas Ferebee as bombardier and Manhattan Project ordnance expert Capt. William (“Deak”) Parsons as weaponeer. Tibbets personally selected plane number 82 for the mission, and, shortly before taking off at approximately 2:45 AM on August 6, 1945, Tibbets asked a maintenance worker to paint his mother’s name—Enola Gay—on the nose of the aircraft. Two other B-29s accompanied the Enola Gay to serve as observation and camera planes. Once the Enola Gay was airborne, Parsons added the final components to Little Boy. This was done because a number of the modified B-29s had crashed on takeoff, and there was some concern that a crash would cause a fully assembled bomb to detonate, wiping out the installation at Tinian.