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1945: Ending the War

1945: Ending the War

Timeline Image: 
Sea full of ships under way

1945 July 29

The Japanese government rejects the Potsdam surrender demand. Also, the five C-54 transports arrive at Tinian. All components for Little Boy are now on site, but no Fat Man bomb assemblies have yet arrived.

1945 July 26

President Truman issues the Potsdam Declaration, which warns Japan of "prompt and utter destruction" and requires unconditional surrender of the Japanese armed forces. USS Indianapolis delivers Little Boy bomb units, and the U-235 projectile to Tinian Island. Five C-54 transport planes leave Kirtland Air Force Base, Albuquerque with: the Little Boy U-235 target (its final component); the Fat Man plutonium core, and its initiator.

1945 July 24

President Truman discloses the existence of the atomic bomb to Stalin (who had already been informed about it by his spies). Meanwhile, General Leslie Groves drafts the directive authorizing the use of the atomic bombs as soon as bomb availability and weather permit. It lists the following targets in order of priority: Hiroshima, Kokura, Niigata, and Nagasaki. This directive constitutes final authorization for atomic attack, no further orders are issued. Also, The U-235 target for Little Boy is cast at Los Alamos, NM.

1945 July 23

Secretary of War Henry Stimson, in Potsdam for meeting between President Truman and Soviet Premier Stalin, receives current target list. In order of choice it is: Hiroshima, Kokura, and Niigata. He also receives an estimate of atomic bomb availability: Little Boy should be ready for use on Aug. 6, second Fat Man-type by Aug. 24, 3 should be available in September, and more each month - reaching 7 or more in December. Also, first A-bomb test unit dropped by 509th at Tinian, and combat hemispheres for Fat Man are fabricated.

1945 July 17

Potsdam conference of President Harry Truman, British Prime Minister Winston Churchill (succeeded on July 28 by Clement Attlee), and Soviet Premier Josef Stalin begins.

1945 July 19

J. Robert Oppenheimer suggests to General Leslie Groves that the U-235 from Little Boy be reworked into uranium/plutonium composite cores for making more implosion bombs (4 implosion bombs could be made from Little Boy's pit). Groves rejects the idea since it would delay combat use.


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