Japan had turned into Germans strongest ally and their power frightened America, sandwiched between the two countries. Because of this, Roosevelt succeeded in persuading Americans to send both non-military goods and military equipment either to Britain or to any country whose defence he considered necessary to the safety of the USA. In July 1941 the USA stopped all shipments of oil to Japan hoping to weaken the Japanese who imported 80 per cent of their oil from America.
On December 7, 1941 Japan bombed the American Pacific battle fleet in Pearl Harbor. The fleet was totally damaged and over 2,000 men were killed. Japan aimed at seizing the Southeast Asia oil and this attack took place to prevent Americans from stopping them. Therefore, on December 8, 1941, the United States declared war on Japan and, since Japan was Hitlers ally, Hitler declared war on the US. The United States was now fighting on the side of Britain and the Soviet Union (the Allies) against Germany and Japan (the Axis).
America entered the war to win it. To achieve this goal, some measures had to be taken: First of all, the American government implemented a complete reorganization of American economy. Factories started producing tanks, bombers and other war supplies instead of cars and washing machines. Wages and prices were seriously controlled and income taxes were introduced. To gain the war, more powerful weapons were needed. Thus, scientists started working on a top-secret research scheme, code-named the Manhattan Project.
As the White House press release on Hiroshima states, this project was carried on in the United States with British agreement since the USA territories were out of reach of enemy bombing. The director of the laboratory in Los Alamos, New Mexico, where this project developed, was J. Robert Oppenheimer. The aim of the project was to make a nuclear weapon, the atomic bomb, and as soon as possible. First, because the Germans were already working on it, and secondly because it seemed the only means to stop Hitler and the Japanese from destroying the free world, to end the war quickly and to save many human lives.
On April 12, 1945, Roosevelt died and Harry Truman, his vice-president, took over as President of The United States. On July 16, 1945, an atomic bomb was tested in the New Mexico desert. On August 6, 1945 an America bomber, the Enola Gay, dropped an atomic bomb over the Japanese city of Hiroshima (a military base in the words of H. Truman). On August 9, 1945, a second bomb was dropped on the city of Nagasaki. On August 14, 1945, the Japanese surrender put an end to World War II.
Was Harry Trumans decision to drop the bomb, the most destructive weapon ever seen, aright decision? Some people say yes, others answer is no. Even the scientists involved didnt agree about the issue. Most really hoped that the mere possession of such a weapon could be enough to frighten the enemy and stop the war. Before its use on Hiroshima and Nagasaki, a group of them clearly showed their disagreement signing petitions and warning both of the bombs unusual destructive force and of the radioactive fallout which followed the bomb test.
After the damage to Hiroshima and Nagasaki, different opinions could still be heard: We were afraid that Hitler had the bomb first, and we made this bomb, which shortened the war and saved a lot of American and Japanese lives in the Japanese war (Victor Weiskopf, physicist). If I had known that the Germans would not succeed in constructing the atomic bomb, I would have never lifted a finger (Albert Einstein, physicist). I think it was necessary to drop one, but the second one could have easily been avoided. I think Japan would have capitulated anyway (Hans Bethe, physicist).