The atomic bomb was a stunningly powerful new weapon developed during World War II that relied upon nuclear fission—splitting the nucleus of a uranium or plutonium atom—to release a tremendous amount of energy. It played a vital role not only in the surrender of Japan in the Pacific theater of the war but also in the deteriorating relations of the Grand Alliance after the war.
The wartime race for an atomic weapon began in Germany in 1938 when two scientists discovered a way to split uranium atoms and produce atomic fission. The following year, with the threat of a potential Nazi nuclear arsenal in mind, the physicist Albert Einstein successfully persuaded President Franklin D. Roosevelt to undertake an American-sponsored effort to build a bomb. In 1941, the U. S. government’s Oeeice of SciENTific Research and Development began secretly coordinating what became known as the Manhattan Project. Scores of handpicked researchers at universities across the country confirmed that a fission chain reaction was possible by isolating the rarer uranium isotope U-235 from the more common form, U-238, and later found that a new element, plutonium, behaved the same way. Between 1943 and 1945, army general Leslie R. Groves and physicist J. Robert Oppenheimer directed about 120,000 personnel in the $2 billion Manhattan Project at installations in 37 facilities in the United States and Canada. A laboratory at Los Alamos, in the New Mexico desert, was responsible for putting the weapon together.
In July 1945, as tests continued, and two months after Germany surrendered, President Harry S. Truman traveled to Germany to meet with his British and Soviet allies at the Potsdam Coneerence. Among other issues, the “Big Three” leaders discussed how to prosecute the war against the sole remaining Axis power, Japan. At the conclusion of the conference, Truman and new British prime minister Clement Attlee (the Soviets had not yet entered the war against Japan) issued the Potsdam Declaration, which called upon Japan to surrender unconditionally by August 3 or face “prompt and utter destruction,” although not specifically mentioning the atomic bomb, which had just been successfully tested at Alamogordo. Nor did Truman explicitly inform Soviet leader Joseph Stalin about the bomb (the British had been involved in the project). Rather, as the conference neared its end, Truman (as he later wrote) “casually mentioned to Stalin that we had a new weapon of unusual destructive force.” Stalin, who knew about the Manhattan Project because of Soviet espionage, gave little reaction.
As the bomb moved from a potential weapon to an actual one in the spring and summer of 1945, questions arose over whether and how to use the bomb against Japan. It had generally been assumed by policymakers that the bomb would be a legitimate weapon of war, but the reality of the bomb and its immense power reopened the issue. Some of the very scientists who helped create the bomb, Oppenheimer among them, argued for restraint. Others advised Truman to demonstrate the bomb for spectators at a disclosed site or issue a warning to Tokyo. Army Chief of Staff General George C. Marshall, however, argued that using the awesome weapon was preferable to accepting a large number of Allied casualties in an invasion of Japan. The excessive brutality of the Pacific war, anger at Japan, and racial antagonisms also contributed to the decision. So did worsening Soviet-American relations, for some American policymakers believed that using the bomb would impress the Soviets with American power and resolve and make them more amenable to cooperating on the host of postwar issues facing the Grand Alliance and causing disagreement and tension. Although he admitted “that an atomic bomb explosion would inflict damage and casualties beyond imagination,” Truman went ahead with the prior decision to use it.
On August 6, 1945, the B-29 bomber Enola Gay dropped a uranium bomb on Hiroshima, devastating the city and killing up to 50,000 people immediately, with another 50,000 or more dying soon thereafter. Still, the Japanese refused to accept surrender terms. On August 8, the Soviet Union declared war against Japan. On August 9, the United States dropped a plutonium bomb, this time on the port city of Nagasaki, killing at least 50,000, and injuring another 60,000 (see Hiroshima and Nagasaki). In the face of the new atomic threat, the emperor intervened and offered surrender.
Almost immediately, the atomic bomb began to affect the postwar American economy, foreign policy, domestic affairs, and popular culture. Scientists, cultural critics, and government officials debated control over atomic knowhow. Some cold war anticommunists saw the American atomic monopoly as a way to forestall Soviet aggression and intimidation. Idealistic opponents, however, believed that atomic power was so awesome that only international control could preserve the fragile peace. In 1949, the Soviets shocked Americans when they detonated their first atomic device. This event contributed to the United States adopting a more stringent form of containing communism, launched the development of a hydrogen bomb, and sparked investigations into spying at Los Alamos.
The atomic bomb also triggered conflicting feelings of optimism and fear. In the 1950s, the government promoted atomic energy as an efficient, clean, inexpensive form of power. Unrealistic innovators foresaw a nuclear utopia where atomic power fueled kitchen appliances and automobiles. Others acknowledged the potential danger of radiation fallout by building bomb shelters. All the while, the government’s civil defense program assured Americans that fear had been exaggerated and that the peaceful atom could bring benefits to all.
Issues of control gradually gave way to the threat of proliferation. While the atomic bomb ignited the superpowers’ nuclear arms race, other nations also sought atomic technology. Despite a global nuclear nonproliferation treaty, by the end of the 20th century no fewer than two dozen countries possessed nuclear weapons, many of which were used for leverage against old regional enemies.
Further reading: Richard Rhodes, The Making of the Atomic Bomb (New York: Simon & Schuster, 1986); Martin J. Sherwin, A World Destroyed: The Atomic Bomb and the Grand Alliance (New York: Knopf, 1975); Allan M. Winkler, Life Under a Cloud: American Anxiety about the Atom (New York: Oxford University Press, 1993).
—Andrew J. Falk
World History
