Another public reason was that the Japanese treated US prisoners of war very badly. The prisoners were used for slave labour, tortured and generally treated very cruelly. About 27% of American prisoners died in Japanese hands. The Americans were enraged and to stop this cruelty and also to get revenge was another reason for them dropping the atom bomb.
Even though Japan was obviously losing the war, they were not giving in. There had been 5 bombings of Tokyo and still no submission from Japan. In Japanese culture it is dishonourable to surrender so despite facing destruction they would not do so. Also, the bravery of the Japanese troops and the Kamikaze pilots meant the Japanese were hard to scare into submission, and many times America met fierce resistance from the Japanese soldiers. They would fight even in the face of obvious defeat until the last man died. America saw it as them having no choice but to drop the atom bombs if they wanted Japan to surrender.
Without the bombs it was going to be a costly victory for America in terms of men and equipment. Japan occupied many islands across the West Pacific that each had to be reoccupied. America met fierce resistance while trying to do this; for example, when trying to occupy Okinawa there was no way of getting the 65 000 Japanese soldiers out except by killing them one by one. This cost over 7 000 American lives which was extremely worrying to the American government. America’s official reason for dropping the atom bombs was that the deaths caused by the bombs would be far less that the deaths caused if the Japanese were not forced to surrender. There had already been a loss of hundreds of thousands of men and America was unwilling for any more American lives to be lost. There was lowering morale within the US soldiers and people were getting tired of the war. It was though that if they didn’t drop the bombs the Japanese would continue to fight tirelessly meaning that defeat would probably take another 18 months and would claim another million lives. America wanted to just get the war over and done with. However, it is thought that although American lives were saved because there was no full scale invasion of Japan, this was not because of the dropping of the atom bombs. The Japanese agreed to surrender because Truman dropped the demand for unconditional surrender, and allowed the Emperor to stay on the throne. Truman could have done this before the dropping of the bomb.
Another reason for dropping the bomb was to prevent the Soviet Union from gaining influence in Japan. Despite the USA and the USSR being allies there was distrust between them as one was a capitalist democracy and the other a communist dictatorship. After the war it was clear these two nations would dominate, but because America feared a spread of communism it wanted to prove to Russia that they were bigger and more powerful, and to stop Japan becoming communist after the war. Russia was already preparing to invade Manchuria. It was feared that once Russia gained Japanese territory it would spread its influences into such areas as Korea, and would upset the balance of power in the East. America would want Japan for trade and because of communist rules Japan would not be open to trade if the USSR had influence or control over it. By dropping the bomb this would prove to Russia that America was the stronger nation and would be the one with influence over Japan after the war. It can be argued that this is another reason for the dropping of the atom bombs. The American Secretary of State, James Byrnes was recorded of saying that the bomb would ‘make Russia more manageable. However this was not an official reason put forward by America so was private, but there was a general fear of communism throughout the American public.
Some say that another private reason was that the bombs were dropped in order to test them. The Manhattan Project which was the project of developing the bombs cost the USA 2 billion pounds and this seemed like a good chance for the USA to use them. They wanted to test them because the effects of the bombs were unknown. One bomb was uranium and the other plutonium, and America wanted to compare the affects. This might be their last chance to test the bomb on people. This reason was kept secret from the public. The USA also wanted to be the first nation to use nuclear weapons, and to win the arms race of The Second World War. This race was between Germany and America, but Germany by 1941 made the decision to abandon their research. However America did not know this and continued with their development of the bombs for fear that the Nazis would be the first to use nuclear weapons. America wanted to be the first to drop the bombs to prove their power to the rest of the world, and especially to Soviet Russia.
I think that the most important reason for the USA using nuclear weapons against Japan was to end the war quickly and to prevent any more loss of American soldiers. Thus America dropped the atom bombs even though American victory was almost certain anyway. This seems to be the most plausible reason the Americans were using for dropping the bombs, although at the same time they were showing their power to the world, especially the USSR, and stopping Russia from claiming Japan.