1945: The United States becomes the first (and remains the only) country ever to use an atomic weapon in warfare, obliterating the Japanese city of Hiroshima and instantly killing 70,000 people. (Many thousands more would die later from the effects of radiation poisoning.) Three days later, the port city of Nagasaki is destroyed by a second atom bomb with the ultimate loss of 140,000 lives. Japan surrenders shortly thereafter, ending World War II.
Several countries, including Nazi Germany, had pursued the development of an atomic weapon but none matched the U.S. Manhattan Project in terms of the resources, energy or scientific manpower devoted to making the bomb a reality.
The atomic age dawned with the discovery of fission in a Berlin laboratory in 1938, news that alarmed many émigré scientists who had come to the United States to escape Nazism. Fearing that Germany might be first to actually develop this ultimate weapon, they appealed to President Franklin D. Roosevelt to make nuclear research a high priority. After some initial skepticism, FDR was persuaded and a joint civilian-military committee was formed, which led to the establishment of the Manhattan Project.
Development of the bomb followed two paths, one using uranium-235, which occurs naturally, and the other man-made plutonium. In the end, both were built and used: The uranium-based "Little Boy" was dropped on Hiroshima, while the plutonium-based "Fat Man" laid waste to Nagasaki.
How heavily populated cities came to be chosen as the targets remains a matter of controversy. The scientists involved in developing the bomb favored demonstrating their weapon to the Japanese in an isolated area, but military and political planners rejected the idea, arguing that the shock of total destruction would have a more profound impact.
The United States maintains to this day that the decision to drop the bomb was made primarily to avoid the necessity of invading the Japanese home islands, an undertaking that would have resulted in enormous casualties on both sides. But that argument ignores the deterioration of Japanese resolve by that point in the war.
Although the emperor's government rejected the Potsdam Declaration in late July, which called for an immediate and unconditional surrender, the Japanese had been sending out peace feelers through the Soviet Union, and early signs of starvation, even on the main island, were apparent.
Many historians believe that the real U.S. motive for dropping the bomb was to end the war quickly before the Russians could become involved, thereby denying them a postwar stake in the Pacific -- and, by practical example, to send a message to Stalin.
Whatever the reasons, the bombs were dropped, and most of the scientists involved in the Manhattan Project later expressed remorse for what they had wrought.
Source: The Manhattan Project: An Interactive History
Photo: A victim of the first atomic bomb ever used in warfare is seen in September 1945, at the Ujina Branch of the First Army Hospital in Hiroshima, Japan. The explosion's thermic rays burned the pattern of this woman's kimono upon her back.
Associated Press
This post first appeared on Wired.com Aug. 6, 2007.
