American and Western mistrust of the USSR (Western fear of the USSR influence)
1. The Soviet withdrawal from the First World War in 1917.
2. The Soviet attempts to set up communist governments in Eastern Europe in the last stage of the Second World War
When Germany was about to be defeated, Churchill, Roosevelt and Stalin met at Yalta in February 1945. Because of the conference, the Soviet Union was allowed to liberated Eastern Europe. Churchill and Roosevelt became more worried that the Soviet would expand her area of influence in the region. But they had to tolerate Soviet demands in return for Stalin's support in the War against Japan.
By the end of the war, the Soviet boundary had been extended into Polish territory. The Soviet also gained land from Finland, Lithuania, Latvia, Estonia, Czechoslovakia and Rumania. The Soviet advance into Eastern Europe further damaged the Soviet-Western relations.