Several events fueled the suspicion and mistrust between the Western powers and the Soviet Union: the Bolshevik challenge to capitalism and the Polish-Soviet war were the most important. As a result, Soviet-American relations became an important and continuing issue of concern for the leaders of both countries.
A week after the end of the Potsdam Conference, the atomic bombings of Hiroshima and Nagasaki increased the Soviet distrust of the United States, when shortly after the attacks. Stalin protested to US government personnel, as Truman's decision left the Soviets almost with no real influence on occupied Japan.