The Manhattan Project was the code name for the U.S. effort during World War II to produce the atomic bomb. The program was organized after nuclear fission was discovered by German scientists in 1938, and many U.S. scientists expressed the fear that Hitler would attempt to build a fission bomb.
The project began in 1942 under the direction of physicist J. Robert Oppenheimer. A successful test explosion took place at White Sands Proving Grounds, in New México, on July 16,1945, two months after Germany surrendered. But the war against Japan was still in progress. Fearing that many thousands of American lives would be lost if Allied forces had to invade Japan, U.S. president Harry S. Truman ordered the use of atomic bombs, resulting in the destruction of the Japanese cities of Hiroshima on August 6 and Nagasaki on August 9. The Japanese surrendered on September 2.
