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American History Timeline
The Manhattan Project

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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