American History Timeline
The Manhattan Project
| DATE | EVENT |
| 1931 | Heavy Hydrogen or deuterium is discovered by Harold C. Urey. |
| 1932 | The atom is split by John Crockcroft and E.T.S. Walton of Great Britain thereby proving Einstein's Theory of Relativity. |
| 1933 | Hungarian physicist Leo Szilard realizes the possibility of the nuclear chain reaction. |
| 1934 | The first nuclear fission is achieved by Enrico Fermi of Italy. |
| 1939 | The Theory of Nuclear Fission is announced by Lise Meitner and Otto Frisch. |
| January 26, 1939 | At a conference at George Washington University, Niels Bohr announces the discovery of fission. |
| January 29,1939 | Robert Oppenheimer realizes the military possibilities of nuclear fission. |
| August 2, 1939 | Albert Einstein writes to President Franklin Roosevelt concerning the use of uranium as a new source of energy leading to the formation of the Committee on Uranium. |
| September 1, 1939 | World War II Begins. |
| February 23, 1941 | Plutonium is discovered by Glenn Seaborg. |
| October 9, 1941 | FDR gives the go-ahead for the development of an atomic weapon. |
| December 6, 1941 | FDR authorizes the Manhattan Engineering District for the purpose of creating an atomic bomb. This would later be called the 'Manhattan Project'. |
| September 23, 1942 | Colonel Leslie Groves is placed in charge of the Manhattan Project. J. Robert Oppenheimer becomes the Project's Scientific Director. |
| December 2, 1942 | First controlled nuclear fission reaction is produced by Enrico Fermi at the University of Chicago. |
| May 5, 1943 | Japan becomes the primary target for any future atomic bomb according to the Military Policy Committee of the Manhattan Project. |
| April 12, 1945 | Franklin Roosevelt dies. Harry Truman is named the 33rd President of the US. |
| April 27, 1945 | The Target Committee of the Manhattan Project select four cities as possible targets for the atomic bomb. They are: Kyoto, Hiroshima, Kokura, and Niigata. |
| May 8, 1945 | War ends in Europe. |
| May 25, 1945 | Leo Szilard attempts to warn President Truman in person concerning the dangers of atomic weapons. |
| July 1, 1945 | Leo Szilard begins a petition to get President Truman to call off using the atomic bomb in Japan. |
| July 13,1945 | American intelligence discovers the only obstacle to peace with Japan is 'unconditional surrender'. |
| July 16, 1945 | The world's first atomic detonation takes place in the 'Trinity Test' at Alamogordo, New Mexico. |
| July 21, 1945 | President Truman orders atomic bombs to be used. |
| July 26, 1945 | Potsdam Declaration is issued, calling for the 'unconditional surrender of Japan'. |
| July 28, 1945 | Potsdam Declaration is rejected by Japan. |
| August 6, 1945 | Little Boy, a uranium bomb, is detonated over Hiroshima, Japan. It kills between 90,000 and 100,000 people immediately. Harry Truman's Press Release |
| August 7, 1945 | U.S. decides to drop warning pamphlets on Japanese cities. |
| August 9, 1945 | The second atomic bomb to hit Japan, Fat Man, was scheduled to be dropped at Kokura. However, because of poor weather the target was moved to Nagasaki. |
| August 9, 1945 | President Truman addresses the nation. |
| August 10, 1945 | U.S. drops warning leaflets on Nagasaki. |
| September 2, 1945 | Japan announces its formal surrender. |
| October, 1945 | Edward Teller approaches Robert Oppenheimer to aid in the building of a new hydrogen bomb. Oppenheimer refuses. |
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