After World War II began in 1939, President Franklin Delano Roosevelt announced the neutrality of the United States. Many people in the United States thought that their country should stay out of the war. The people wanted the Allied Forces to have the victory. President Roosevelt also wanted an Allied victory because an Axis victory might endanger democracies everywhere. The United States equipped nations fighting the Axis with ships, tanks, aircraft, and other war materials. The Axis did not like this. Japan wanted to take over China, but China refused. China was led by Chiang Kai-Shek at the time. Japan wanted the United States to stop sending China supplies, but the United States refused. The United States opposed the expansion of Japan in Asia, so they cut off important exports to Japan.
General Hideki Tojo was the Premiere of Japan. He and other Japanese leaders did not like the fact that Americans were sending war supplies to China and other countries in Asia. A surprise attack was ordered by Japan on December 7, 1941. The target was the U.S. naval base at Pearl Harbor, Hawaii. 360 planes bombed the naval base killing about 3,000 people and destroying many warships, aircraft carriers, and submarines. This was a catalyst that brought the United States into World War II.
Albert Einstein predicted that mass could be converted into energy early in the century and was confirmed experimentally by John D. Cockcroft and Ernest Walton in 1932. In 1939, Otto Hahn and Fritz Strassmann discovered that neutrons striking the element uranium caused the atoms to split apart. Physicists found out that among the pieces of a split atom were newly produced neutrons. These might encounter other uranium nuclei, caused them to split, and start a chain reaction. If the chain reaction were limited to a moderate pace, a new source of energy could be the result. The chain reaction could release energy rapidly and with explosive force.
Leo Szilard, Eugene Wigner, and Edward Teller, Hungarian-born physicists were frightened by the possibility that Germany might produce an atomic bomb. They insisted that Albert Einstein inform President Roosevelt about the possibility of the Germans making an atomic bomb. In late 1939 President Roosevelt ordered an American effort to make an atomic bomb before the Germans. This project to produce the atomic bomb was named the Manhattan Project. Industrial and research activities took place at such sites as Los Alamos, New Mexico; Oak Ridge, Tennessee; and Hanford, Washington. The Manhattan Project was led by J. Robert Oppenheimer. Oppenheimer directed the design and building of the bomb. He and other scientists worked on this project from 1943 to 1945. He was known as the father of the atomic bomb. The first atomic bomb was successfully exploded on July 16, 1945, near Alamogordo, New Mexico.
President Franklin Delano Roosevelt died on April 12, 1945. Vice President Harry S. Truman became President of the United States because of the death of Roosevelt. On May 7, 1945 Germany surrendered. Truman proclaimed May 8 as V-E Day (Victory in Europe Day). In July, President Truman went to Potsdam, Germany, to discuss war issues with Prime Minister Churchill of Great Britain and Premier Stalin of the Soviet Union. During his time in Posdam, the President received secret word that the atomic bomb had been successfully tested. On his way back to the United States, President Truman ordered American fliers to drop an atomic bomb in Japan.
On August 6, 1945, a B-29 Superfortress named Enola Gay left the Pacific island of Tinian to bomb the Japanese city of Hiroshima. The Enola Gay was named by the pilot, Colonel Paul Tibbets, after his mother. The crew of Enola Gay were told that no one could be sure what would happen when the atomic bomb was dropped over Hiroshima. The atomic...