By the summer of 1945, World War II in the Pacific was virtually over. Since December 1941, the United States had pushed Japanese forces back until only the homeland itself remained in Japanese control.
The United States prepared to launch an invasion of Japan. While preparing for the invasion, on July 26 U.S. president Harry S. Truman and British prime minister Clement Attlee, with Nationalist Chinese president Chiang Kai-shek concurring, issued the Potsdam Declaration calling for the unconditional surrender of Japan and listing additional peace terms. At this point Truman knew that the first atomic bomb test at Alamogordo, New Mexico, had been successful 10 days earlier.
The test was the culmination of a three-year highly secret project. The first man-made atomic reactor was built in a squash court at the University of Chicago in 1942. More sophisticated reactors were built at Hanford, where the plutonium was produced. The first test of the plutonium bomb was at Alamogordo on July 16, 1945.
Although the Potsdam Declaration made it clear to the Japanese that they could anticipate severe consequences if they chose to continue the war, Japan rejected the ultimatum. Truman ordered the use of the bomb. His secretary of war, Henry L. Stimson, regarded the use of the bomb as less abhorrent than sacrificing U.S. lives. Truman’s military advisers had indicated that the invasion of Japan could result in the loss of half a million U.S. soldiers plus millions of Japanese military and civilian lives. Truman wanted the war over, and he wanted the maximum possible blow in order to end the war without the invasion. The U.S. military selected Hiroshima and Kokura because the two were among the Japanese cities that had thus far escaped the destruction caused by U.S. and Allied bombs.
On August 6, 1945, at 9:15 a.m. Tokyo time, the B-29 bomber Enola Gay, piloted by Paul W. Tibbets, dropped a uranium atomic bomb, “Little Boy,” on Hiroshima. In minutes half of Japan’s seventh-largest city was gone, and thousands of people were dead. Between 60,000 and 70,000 people were dead or missing, and 140,000 were injured.
On August 6 another bomb was prepared on Tinian Island. On August 9 the B-29 Bock’s Car prepared to bomb Kokura. Smoke over the target caused pilot Sweeney to seek his alternate target, Nagasaki.
The industrial city of Nagasaki fell to the bomb “Fat Man” at 11:02 a.m. Exploded at 1,800 feet to maximize the impact of the blast, Fat Man leveled buildings, destroyed electrical systems, and generated fires. The bomb destroyed 39 percent of the city, killed 42,000, and injured 40,000.
The two bombings killed 210,000 Japanese—140,000 in Hiroshima and 70,000 in Nagasaki, two thirds of them women, children, and elderly. Deaths to military and foreign workers are unknown. What is known is that the explosion rather than the radiation was the primary cause of death. Some 24 Australian prisoners of war about 1.5 kilometers from Nagasaki ground zero survived, many to old age.
The bombs produced fires, blast pressure, and extremely high radiation levels. Both were detonated about 600 meters aboveground, so the belowground contamination was minimal from the bombs. Subsequent rainfall deposited radioactive material east of Nagasaki and west and northwest of Hiroshima, but the great majority of the radioactive material was taken high into the atmosphere by the blasts themselves. The blasts also irradiated some stable metals—such as those found in metal roofs—for a day or two after the blast, but the damage was minimal.
In the cities victims died due to fl ash burns from the heat generated by the blast. People died when their homes burst into flames. Others were injured by flying debris. In Hiroshima a firestorm arose in the center of the devastation. People within 300 yards of ground zero were vaporized, leaving their shadows on the streets. Blast and heat also stripped skin off bodies, sucked out eyeballs, and burst stomachs. Radiation deaths in subsequent years totaled about 120,000.
Severe radiation produced death within days. Severe radiation injuries were suffered by all persons within a one-kilometer radius. At between one and two kilometers distance injuries were serious to moderate, and slight injury affected those within two to four kilometers
In addition to the 103,000 killed by the bombs in the first four months, another 400 died from cancer and leukemia over the subsequent 30 years. The bombs also produced birth defects and stillbirths. The children of survivors seem to have suffered no genetic damage. As of 2004, 93,000 exposed survivors were being monitored.
On September 2, 1945, the Japanese government surrendered unconditionally. Winston Churchill calculated that the bomb had saved the lives of 250,000 British and 1 million Americans.
Harry Truman’s argument that the bomb would save half a million soldiers was unconvincing to critics, who in the years since have noted that the Japanese were prepared to ask for peace before the bombs were dropped and had already sought peace in previous months. To these critics, the real reason for the use of the bombs was Truman’s desire to frighten and impress the Soviet Union, which was already moving from ally to rival. Truman wanted to end the war before the Soviets could enter the Pacific War and stake a claim to a piece of the postwar settlement.
The Hiroshima bomb used 60 kilograms of highly enriched uranium-235 to destroy about 90 percent of the city. The Nagasaki bomb used 8 kilograms of plutonium-239. The bombs were a thousand times more powerful than any exploded previously. Four years later the United States exploded the first hydrogen bomb, and it was not long before there were bombs a thousand times more powerful than the one that was dropped on Hiroshima. By the 1980s the world’s arsenals included a million Hiroshima bombs.
The Soviet Union tested its atomic bomb in 1949, and quickly Great Britain, France, and China joined the atomic community.
Beginning in the 1950s the emphasis was on the use of atomic energy for electricity and medical purposes. In the early 21st century 16 percent of the world’s electricity, including that of Hiroshima and Nagasaki, came from atomic power.
John H. Barnhill