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Harold C. Urey discovers Heavy Hydrogen (deuterium).
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John Crockcroft and E.T.S. Walton, of Great Britain, split the atom, thereby proving Einstein's Theory of Relativity.
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Leo Szilard, a Hungarian physicist, realizes the possibility of a nuclear chain reaction.
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Timeline of Hitler’s march to conquer the world
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Enrico Fermi, of Italy, produces the first nuclear fission.
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Lise Meitner and Otto Frisch announce the Theory of Nuclear Fission.
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The Neutrality Act was put in place to keep the U.S. out of the war, so the cash and carry system was created to enable the U.S. to help allies without getting involved.
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Niels Bohr announces the discovery of fission in a conference at George Washington University.Robert Oppenheimer then realizes the military possibilities of nuclear fission.
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Albert Einstein writes to President Franklin Roosevelt concerning the use of uranium as a new source of energy and urging the development of an atomic research program. Roosevelt did not see the use of such a program, but did agree to proceed with the idea, leading to the formation of the Committee on Uranium.
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Glenn Seaborg discovers Plutonium.
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The Lend lease act passed congress, which was proposed by FDR to improve the U.S. economy and help their allies even more by lending them military supplies.
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FDR gives the go-ahead for the development of an atomic weapon.
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FDR authorizes the Manhattan Engineering District for the purpose of creating an atomic bomb, and the American effort to design and build an atomic bomb revives its code name, "The Manhattan Project"
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Japanese bombed Pearl Harbor, Hawaii, destroying nearly the entire U.S. Pacific fleet, hundreds of airplanes, and killing about 2,500 military personnel and civilians.
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U.S. congress declares war on Japan at the request of FDR in response to the bombing of Pearl Harbor.
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Manhattan Project is placed under the control of Colonel Leslie Groves and J. Robert Oppenheimer becomes the Project's Scientific Director.
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First controlled nuclear fission reaction is produced by Enrico Fermi at the University of Chicago.
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According to the Military Policy Committee of the Manhattan Project, for any future atomic bomb, Japan would be the primary target
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Invasion of Normandy.
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Franklin Roosevelt dies a few hours after suffering a massive cerebral hemorrhage. Harry Truman is named the 33rd President of the US.
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The Target Committee of the Manhattan Project selected four cities as possible targets for the atomic bomb. They are: Kyoto, Hiroshima, Kokura, and Niigata.
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Leo Szilard attempts to warn President Truman in person concerning the dangers of atomic weapons.
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Leo Szilard begins a petition to get President Truman to call off using the atomic bomb in Japan.
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The world's first atomic detonation takes place in the 'Trinity Test' at Alamogordo, New Mexico.
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President Truman orders atomic bombs to be used. Considered to be the most difficult decision of his life.
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Potsdam Declaration is issued, demanding an unconditional surrender by Japan.
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Japan refused the declaration even with the threat of total destruction.
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The First atomic bomb named "Little Boy" was dropped from the plane "Enola Gay" on Hiroshima, Instantly killing 70,000 Japanese/
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U.S. decides to drop warning pamphlets on Japanese cities.
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The second atomic bomb named "Fat Man" was dropped on Nagasaki, instantly killing 80,000 Japanese. Original target was Kokura, but poor weather forced the target to change.
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U.S. drops warning leaflets concerning another atomic bomb on Nagasaki, the day after the bomb was dropped, even though the U.S. was out of atomic bombs and had no way of producing any more at the time.
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