The End of World War II
As the designs of Fat Man and Little Boy were finalized in early 1945, planning began for their use in combat against Japan. In March a special team, known as Project A (Alberta) and led by future Nobel Laureate Norman Ramsey, was created to handle the transfer of the bomb's components to Tinian Island, where they would be assembled for use against Japan.
Project A had the mission of assuring "the successful combat use of an atomic bomb at the earliest possible date after a field test of an atomic explosion and after the availability of the necessary material."
Only a few months after the assault by United States Marines, Tinian had become the largest B-29 Bomber base in world. Part of the island was reserved for the Project A team as well, and the Army Air corps 509th Composite Group, the military unit that would carry out the combat missions. Construction of the facilities for these two units began in April 1945 and was completed in June. The most important facility was an air-conditioned assembly building — the only one of its kind on the island. The first shipments of non-nuclear bomb components, known by the code names Bowery and Bronx, started arriving in July.
IShortly after the Trinity Test, the nuclear components for Little Boy were shipped to Tinian on the Navy's heavy cruiser, the USS Indianapolis. The parts were successfully delivered on July 26th. Four days later, the Indianapolis was sunk in the Philippine Sea by a Japanese submarine. Only 316 sailors out of a crew of 1200 survived. Once the Fat Man design was successfully tested at Trinity, the nuclear parts for a combat unit were flown to Tinian C-54 cargo planes operated by the 509th's Green Hornet squadron.
The Target Committee
The targets for the Little Boy and Fat Man had been selected months earlier. A committee formed by General Groves selected four cities based on the following criteria:
- Targets had to possess sentimental value in the mind of the Japanese people.
- Targets had to have some military significance
- Targets had to be largely intact, to demonstrate the awesome destructive power of an atomic bomb.
- The target had to be large in size, suitable for attack by a weapon of an atomic bomb's magnitude.
Hiroshima was selected because it was the largest target available with the largest population. In addition, it served as a port of embarkation for the Japanese Army and was an industrial center, complete with large factories and many smaller production facilities. Hiroshima was also the headquarters of the Japanese 2nd Army, which stood poised to meet an Allied invasion.
Hiroshima and Nagasaki
Little Boy was ready for combat on August 1st, but bad weather stopped air operations from Tinian. On August 5th, the weather began clearing, and last minute preparations were completed. Lieutenant Colonel Paul Tibbets, the commanding officer of the 509th, would pilot the strike aircraft, which was named after his mother, Enola Gay. Los Alamos Ordnance Division Leader Navy Captain William S. Parson, was the bomb commander and responsible for arming Little Boy once the Enola Gay had successfully taken off.
On August 6, at 9:09 am, the Enola Gay came within site of Hiroshima. Parsons, who kept a log of the flight, had armed the bomb almost two hours before. At 9:15, the bomb was released. The force of the explosion rocked the plane, even though it had maintained an altitude of more than 30,000 feet. The following day, Parsons wrote a letter to his father describing the scene: "The base of the cloud looked like boiling dark colored dust and it covered the city proper," continuing, "Right under our bomb was the southern headquarters of the Jap army. Although the cloud was impenetrable, throughout the day, I have no doubt that the Jap army headquarters in Hiroshima no longer exists."
Groves had predicted it would take two bombs to force the Japanese to surrender. The first would stun the enemy, and the second would demonstrate the United States' ability to produce more than one atomic bomb. His prediction proved accurate. The second atomic mission was scheduled for August 11th, but this date was moved up two days on the basis of weather predictions. Bockscar, commanded by Major Charles Sweeney, took off at 3:47 am on August 9 for Kokura, a military arsenal and the center of Japanese steel production. According to the bombardier's log, Kokura "was obscured by heavy ground haze and smoke." Bockscar made three runs over the city, but failed to positively identify the target. Sweeny and Bomb Commander, Frederick Ashworth, changed course for the secondary target, Nagasaki. The weather at Nagasaki was acceptable, but far from favorable. Fat Man was dropped at 11:58, more than eight hours after the aircraft had taken off from Tinian. Fat Man destroyed less of Nagasaki than Little Boy had of Hiroshima. However, the bomb wrecked Nagasaki's heavy industrial complexes, including two massive Mitsubishi factories.
The Japanese Surrender
The Emperor, shocked by the devastating effects of the atomic bombings, called for his government to sue for peace through the Swiss embassy. In a note to Secretary of State James Byrnes, dated August 10, 1945, the Japanese Minister to Switzerland wrote, "The Japanese Government are ready to accept the terms enumerated in the joint declaration which was issued at Potsdam on July 26th, 1945 … with the understanding that the said declaration does not comprise any demand which prejudices the prerogatives of His Majesty as a Sovereign Ruler." Byrnes promptly responded the next day, outlining the proposed role of the Emperor in the days to come: "From the moment of surrender the authority of the Emperor and the Japanese Government to rule the state shall be subject to the Supreme Commander of the Allied powers," concluding, "The ultimate form of government of Japan shall, in accordance with the Potsdam Declaration, be established by the freely expressed will of the Japanese people." Fighting ended on August 14, 1945.