The decision to use the atomic bomb to attack two Japanese cities and effectively end World War II remains one of the most controversial decisions in history. The conventional view, going back to the initial press coverage in 1945, was that the use of atomic weapons was justified as it ended a long and very costly war. However, over the intervening decades, other interpretations of the decision to strike two Japanese cities have been offered.

Alternative explanations include the idea that the United States was largely interested in using atomic weapons as a way of ending the war quickly and keeping the Soviet Union from getting involved in the fighting in the Pacific.

Fast Facts: Decision to Drop the Atomic Bomb

  • President Truman made the decision to use the atomic bomb with no public or congressional debate. He later formed a group known as the Interim Committee to decide how—but not whether—the bomb should be used.
  • A small group of renowned scientists, including some involved in the creation of the bomb, advocated against its use, but their arguments were essentially ignored.
  • The Soviet Union was set to enter the war in Japan within months, but the Americans were wary of Soviet intentions. Ending the war quickly would prevent Russian participation in the fighting and expansion into parts of Asia.
  • In the Potsdam Declaration, issued on July 26, 1945, the United States made a call for the unconditional surrender of Japan. Japan’s rejection of the demand led to final order to proceed with atomic bombing.

Truman’s Options

When Harry Truman became president after the death of Franklin D. Roosevelt in April 1945, he was informed of a momentous and extraordinarily secret project: the development of the first atomic bomb. A group of scientists had approached Roosevelt years earlier, expressing fear that Nazi scientists would develop an atomic bomb. Eventually, the Manhattan Project was organized to create an American super weapon fueled by an atomic reaction.

By the time Truman was informed of the Manhattan Project, Germany was nearly defeated. The remaining enemy of the United States, Japan, continued fighting in an incredibly bloody war in the Pacific. In early 1945, campaigns on Iwo Jima and Okinawa proved very costly. Japan was being heavily bombed by formations of a new bomber, the B-29. Despite heavy casualties, especially among Japanese civilians killed in an American incendiary bombing campaign, the Japanese government seemed intent on continuing the war.


In the spring of 1945, Truman and his military advisers had two obvious options. They could resolve to fight a prolonged war against Japan, which would probably mean having to invade the Japanese home islands in late 1945 and perhaps even continue fighting into 1946 or beyond. Or they could continue working on acquiring a functional atomic bomb and seek to end the war with devastating attacks on Japan.

Lack of Debate

Before the atomic bomb was used for the first time there was no debate in Congress or among the American public. There was a simple reason for that: almost no one in Congress had been aware of the Manhattan Project, and the public had no inkling that a weapon that could end the war was on the horizon. Even the many thousands who worked on the project at various labs and secret facilities were unaware of the ultimate purpose of their labor.

Yet in the summer of 1945, as the atomic bomb was being prepared for its final testing, a closely contained debate over its use did emerge within the circle of scientists who had contributed to its development. Leo Szilard, a refugee Hungarian physicist who had petitioned President Roosevelt to begin work on the bomb years earlier, had grave concerns.

The main reason Szilard had urged the United States to begin work on the atomic bomb was his fear that Nazi scientists would develop nuclear weapons first. Szilard and other European scientists who worked on the project for the Americans had considered the use of the bomb against the Nazis to be legitimate. But with Germany’s surrender in May 1945, they had concerns about using the bomb against Japan, which did not seem to be developing its own atomic weapons.

Szilard and physicist James Franck submitted a report to Secretary of War Henry L. Stimson in June 1945. They argued that the bomb should be not be used against Japan without warning, and that a demonstration explosion should be arranged so the Japanese leadership could understand the threat. Their arguments were essentially ignored.

The Interim Committee

The secretary of war formed a group called the Interim Committee, which was tasked with deciding how the bomb was to be used. The issue of whether it should be used was not really an issue. The thinking in the highest levels of the Truman administration and the military was quite clear: if the atomic bomb could shorten the war, it should be used.

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