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That same day, the Potsdam Declaration was issued by the U.S., Britain and Nationalist China, the three countries at war with Japan. The document offered the enemy "an opportunity to end this war." Its language was blunt: "Following are our terms. We will not deviate from them. There are no alternatives. We shall brook no delay." It concluded, "We call upon the government of Japan to proclaim now the unconditional surrender of all Japanese armed forces ... The alternative for Japan is prompt and utter destruction." Only those who had seen or heard of the atomic bomb, including Truman and Churchill, could understand what the last words might mean.
The Potsdam text reached Tokyo on the morning of July 27 and was debated most of the day by the Japanese leaders. Some saw a possibility of national face saving in that the demand for "unconditional surrender" was linked specifically to the Japanese armed forces and made no mention of Emperor Hirohito. The one condition the Japanese were determined to maintain, at the expense, if need be, of total extinction, was that the revered Hirohito would never be deposed, imprisoned or tried as a war criminal. In the end, the military advisers successfully argued that the Potsdam Declaration must be rejected to keep up the morale of Japan's besieged forces and civilians.
The next afternoon Japan's Prime Minister, Kantaro Suzuki, held a press conference in Tokyo, at which he vowed that his government planned to ignore the declaration and would "resolutely fight for the successful conclusion of the war." But the previous night, the first components of Fat Man, the plutonium-based bomb whose prototype had been tested on July 16, had arrived at Tinian.
By July 30, scrutiny of the Suzuki statement had convinced Washington that Japan would not surrender under the Potsdam terms. Secretary of War Henry L. Stimson cabled President Truman, who was still at the conference, asking for final ratification of the order to drop the atomic bomb, which had been drafted on July 24 by Groves and approved by Stimson and Army Chief of Staff General George C. Marshall. Truman wrote out in longhand a reply for transmission back to Stimson: "Suggestion approved. Release when ready."
Bad weather--a typhoon approached Japan on Aug. 1--only delayed what was now inevitable. The skies cleared gradually. By the afternoon of Aug. 5, on Tinian, Little Boy was being winched into the specially modified bomb bay of a B-29, which Tibbets would christen--in honor of his mother's given names--Enola Gay. The 9,700-lb. bomb was 10-1/2 ft. long and 29 in. in diameter; it looked, one of Tibbets' crew decided, like "an elongated trash can with fins." After a midnight briefing, crews of the seven B-29s assigned to carry out the mission and various support functions had breakfast and then rode by truck to their stations. The strike plane Enola Gay, with Tibbets as pilot, groaned down the runway, picking up speed that would lift its 65 tons into the air. It took off at 2:45 a.m., Tinian time. Only on the way to the target did Tibbets tell his 11-man crew that they were carrying a new kind of bomb.