Stalin did not do as The Big Three, Churchill, Roosevelt and himself, agreed at the Yalta Conference. They agreed that they would hunt down and punish any war criminals who were responsible for the horrors of the Nazi concentration camps. But due to the non-aggression pact signed by Hitler and Stalin in 1939, Stalin did not send any troops to help USA to hold back Hitler in Russia. This worried USA because it was a sign that Stalin was not standing at a totally opposite of Hitler. Under this relationship, Stalin might betray USA and Britain which he should not do. They had also agreed to hold free elections for people to choose the government they wanted to be in their countries. But Stalin set up communist governments in the countries in Eastern Europe. He ignored the wishes of the majority of the people. These actions had offended the agreement between The Big Three.
Stalin had not act according to USA and Britain's expectations either. USA did not expect that Stalin was not withdrawing the Soviet troops in Eastern countries such as the Baltic States, Finland, Poland. Stalin did not listen to Britain and the USA's protest but only following his own desire. He had started to spread Communism. He turned into USA's enemy and continued dominating countries in the Eastern Europe. He claimed that this was the "Soviet sphere of Influence". To him, this sphere of influence meant to invade