The allies all have different ideas which meant they didn't all agree on what should happend next with the Eastern Europe.
United States and Britian wanted a united Germany while Stalin wanted Germany to be a divided country.
Stalin didnt want to give free elections , for Eastern Europe countries that were under Soviet Control at Potsdam. Truman believed that Stalin's goal was to take over the whole world and to convert it all to communism.
Western powers were afraid of the Soviet Expansion