Stalin wanted to cripple Germany completely to protect the USSR against future threats, Truman did not want to repeat the mistake of the Treaty of Versailles
They disagreed over Soviet policy in eastern Europe
Stalin wanted to set up pro-Soviet governments to protect the USSR, Truman saw this as evidence that Stalin wanted to build up a Soviet empire in Europe
Japan refused to consider a surrender to the USA, so on 6 August 1945 the USA dropped the first atomic bomb on Hiroshima, followed by a second attack on Nagasaki on 9 August
Source 11: 'The aftermath of the Hiroshima bomb, August 1945. At least 75,000 were killed instantly. Thousands more died from radiation poisoning in the years that follows'