Surrender of Japan - Manhattan Project

Manhattan Project

In 1939, Albert Einstein and Leó Szilárd wrote a letter to President Roosevelt warning him that the Germans might be researching the development of atomic weaponry and that it is necessary that the United States fund research and development of its own such project. Roosevelt agreed, and the result was the Manhattan Project—a top-secret research program administered by General Leslie Groves, with scientific direction from J. Robert Oppenheimer. The first bomb was tested successfully in the Trinity explosion on July 16, 1945.

As the project neared its conclusion, American planners began to consider the use of the bomb. Groves formed a committee that met in April and May 1945 to draw up a list of targets. One of the primary criteria was that the target cities must not have been damaged by conventional bombing. This would allow for an accurate assessment of the damage done by the atomic bomb.

The targeting committee's list included 18 Japanese cities. At the top of the list were Kyoto, Hiroshima, Yokohama, Kokura, and Niigata. Ultimately, Kyoto was removed from the list at the insistence of Secretary of War Henry L. Stimson, who had visited the city on his honeymoon and knew of its cultural and historical significance.

In May, Harry S. Truman (who had become president upon Franklin Roosevelt's death on April 12) approved the formation of an "Interim Committee", an advisory group that would report on the atomic bomb. It consisted of George L. Harrison, Vannevar Bush, James Bryant Conant, Karl Taylor Compton, William L. Clayton, and Ralph Austin Bard, advised by scientists Oppenheimer, Enrico Fermi, Ernest Lawrence, and Arthur Compton. In a June 1 report, the Committee concluded that the bomb should be used as soon as possible against a war plant surrounded by worker's homes, and that no warning or demonstration should be given.

The Committee's mandate did not include the use of the bomb—its use upon completion was presumed. Following a protest by scientists involved in the project, in the form of the Franck Report, the Committee re-examined the use of the bomb. In a June 21 meeting, it reaffirmed that there was no alternative.