After witnessing the successful test of the first atomic bomb--a primordial burst of energy on the predawn New Mexico desert, a man-made fire bright enough to flicker in reflection off the moon--Brigadier General Thomas F. Farrell sought out his immediate superior, Major General Leslie R. Groves. Groves was commander of the top-secret Manhattan Project, which had been commissioned and funded--with $2 billion--to try to build such a bomb. "When Farrell came up to me," Groves remembered, "his first words were, 'The war is over.' My reply was, 'Yes, after we drop two bombs on Japan.'" This was the morning of July 16, 1945; within anamazing 30 days, both of these statements would be history.
President Truman learned of the bomb test while in Potsdam, a suburb of burned-out and bombed-out Berlin, where he was meeting with Winston Churchill and Joseph Stalin, leaders of the nations allied with the U.S. in the defeat of Nazi Germany. The news that the atomic bomb actually worked promised to solve in a flash two of Truman's most urgent problems in the Pacific: the ordering of a heavy-casualty land invasion of the Japanese home islands, scheduled to begin Nov. 1, and the necessity of making concessions to Stalin in order to secure Soviet military intervention to help speed the defeat of Japan.
The atomic bomb held out the hope that neither action would be necessary. Truman confided to his diary, "It is certainly a good thing for the world that Hitler's crowd or Stalin's did not discover this atomic bomb. It seems to be the most terrible thing ever discovered, but it can be made the most useful." The question of how to deliver and drop atomic bombs on Japanese soil had been thoroughly studied at the highest U.S. government levels well before the test in New Mexico. A list of prospective targets had been drawn up, with an emphasis, as Groves later wrote, on "places the bombing of which would most adversely affect the will of the Japanese people to continue the war." A special Air Force unit--the 509th Composite Group--had been formed in September 1944, under the command of Lieut. Colonel Paul W. Tibbets, regarded by many to be the service's best bomber pilot. Tibbets' group would be responsible for dropping the then untested atomic devices, although few of its 225 officers and 1,542 enlisted men were told the exact nature of their assignment.
On Tinian, a 39-sq-mi. island in the Marianas some 1,500 miles south of Japan, U.S. forces had constructed the largest airport in the world, including four parallel, 8,500-ft.-long runways designed for B-29 Superfortresses. Several of the incendiary-bomb raids on Japanese cities staged by Major General Curtis LeMay's XXI Bomber Command began and ended in the Marianas. Members of the 509th unit started arriving at Tinian in June. On July 26, components of Little Boy, the uranium-based bomb that was scheduled to be dropped first, reached Tinian aboard the U.S. warship Indianapolis.