Manhattan Project: Debate Over How to Use the Bomb, 1945

Time Periods

1890s-1939:
Atomic Discoveries

1939-1942:
Early
Government Support

1942:
Difficult
Choices

1942-1944:
The Uranium
Path to
the Bomb

1942-1944:
The Plutonium
Path to
the Bomb

1942-1945:
Bringing It All Together

1945:
Dawn of the
Atomic Era

1945-present:
Postscript --
The Nuclear Age

DEBATE OVER HOW TO USE THE BOMB
(Washington, D.C., Late Spring 1945)
Events > Dawn of the Atomic Era, 1945

In early May 1945, Secretary of War Henry L. Stimson, with the approval of President Harry S. Truman, formed an Interim Committee of top officials charged with recommending the proper use of atomic weapons in wartime and developing a position for the United States on postwar atomic policy. Stimson headed the advisory group composed of Vannevar Bush, James Conant, Karl T. Compton, Under Secretary of the Navy Ralph A. Bard, Assistant Secretary of State William L. Clayton, and future Secretary of State James F. Byrnes. Robert Oppenheimer, Enrico Fermi, Arthur Compton, and Ernest Lawrence served as scientific advisors (the Scientific Panel), while General George Marshall represented the military. The committee met on May 31 and then again the next day with leaders from the business side of the Manhattan Project, including Walter S. Carpenter of DuPont, James C. White of Tennessee Eastman, George H. Bucher of Westinghouse, and James A. Rafferty of Union Carbide.

At the May 31 meeting, Lawrence suggested that a demonstration of the atomic bomb might possibly convince the Japanese to surrender. This was rejected, however, out of fear that the bomb might be a dud, that the Japanese might put American prisoners of war in the area, or that they might manage to shoot down the plane. The shock value of the new weapon could also be lost. These reasons and others convinced the group that the bomb should be dropped without warning on a "dual target" -- a war plant surrounded by workers' homes. On June 6, Stimson informed President Truman (right) that the Interim Committee recommended keeping the atomic bomb a secret until Japan had been bombed. The attack should take place as soon as possible and without warning. Truman and Stimson agreed that the President would stall if the Soviet Union asked about atomic weapons in the upcoming meetings to be held at Potsdam and that it might be possible to gain concessions from the Soviet Union later in return for providing technical information.

The Interim Committee also discussed the postwar fate of atomic energy. At the May 31 meeting, they concluded that the United States should try to retain superiority of nuclear weapons in case international relations deteriorated. Most present at the meeting thought that atomic secrets should be protected for the present, though they conceded that the United States monopoly could not be held long. The meeting with the industrialists confirmed their view that the United States had a lead of three to ten years on the Soviet Union in production facilities for bomb fabrication. There had been some discussion of free exchange of nuclear research for peaceful purposes and the international inspection system that such an exchange would require. Stimson told Truman that the Interim Committee was considering domestic legislation and that its members generally held the position that international agreements should be made in which all nuclear research would be made public and a system of inspections would be devised. In case international agreements were not forthcoming, the United States should continue to produce as much fissionable material as possible to take advantage of its current position of superiority.

Not all the scientists of the Manhattan Project were satisfied that their voices had been heard in decision-making about the bomb. They had built the bomb and thought they had a right to help determine how it was to be used. The Scientific Panel of the Interim Committee was supposed to be the connection between the scientists and the policymakers, but after the scientists of the Met Lab were briefed by Arthur Compton on June 2 about the Interim Committee's conclusions, the Met Lab decided to create a "second opinion." The result was the Committee on the Social and Political Implications of the Atomic Bomb, which was chaired by James Franck and included Glenn Seaborg and Leo Szilard. Its report argued that postwar international control of atomic power was the only way to stop the arms race that would be inevitable if the United States bombed Japan without first demonstrating the weapon in an uninhabited area. Oppenheimer, Fermi, Compton, and Lawrence (the Scientific Panel) disagreed with the Franck Report, however, and concluded that no technical test would convince Japan to surrender. On June 21, the Interim Committee concurred. The bomb would be used as soon as possible, without warning, and against a war plant surrounded by additional buildings. As to informing the Soviet Union, the Committee concluded that Truman should mention at Potsdam that the United States was preparing to use a new kind of weapon against Japan.

The bomb target selection group was chaired by Leslie Groves, a responsibility he shared with General Thomas Farrell, his military aide since February 1945. In late May, the committee of scientists and Army Air Force officers listed Kokura Arsenal, Hiroshima, Niigata, and Kyoto as the four best targets, believing that attacks on these cities would make a profound psychological impression on the Japanese and weaken military resistance. (None of these cities had yet been bombed by Curtis LeMay's Twentieth Air Force, which planned to eliminate all major Japanese cities by January 1, 1946.) Stimson vetoed Kyoto, Japan's most cherished cultural center, and Nagasaki replaced Kyoto on the target list. Now all that was left was for Truman to give his final approval, and then it would be up to the weather to determine which of these four cities would be the first struck by an atomic bomb.

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Sources and notes for this page.

The text for this page was adapted from, and portions were taken directly from the Office of History and Heritage Resources publication: F. G. Gosling, The Manhattan Project: Making the Atomic Bomb (DOE/MA-0001; Washington: History Division, Department of Energy, January 1999), 45-47. See also Vincent C. Jones, Manhattan: The Army and the Atomic Bomb, United States Army in World War II (Washington: Center of Military History, United States Army, 1988), 530. The photograph of Robert Oppenheimer, Enrico Fermi, and Ernest Lawrence is courtesy the Lawrence Berkeley National Laboratory. Click here for information on the photograph of Ernest Lawrence, Arthur Compton, Vannevar Bush, James Conant, Karl Compton, and Alfred Loomis. The portrait of President Harry S. Truman is courtesy the Truman Presidential Library. The photographs of "Joe 1" (the first Soviet atomic test) and of Leo Szilard with Albert Einstein are courtesy the Federation of American Scientists. The photograph of Leslie Groves and Thomas Farrell is reprinted from Jones, Manhattan, 512.