American and Soviet relations deteriorated in the decade following World War II. The three factors that had the most effect on that relationship were the agreements made at the Yalta Conference, the Korean War, and McCarthyism.
The agreements of the Yalta Conference began the deterioration of the American-Soviet relationship. Some of the decisions taken at Yalta pertained to Europe. The most critical of these had to do with the liberated nations of eastern Europe. Roosevelt and Churchill rejected Stalin’s proposal that they accept the Lublin government in Poland. Instead, the three leaders agreed on a reorganization of the Polish government to include leaders from abroad- this provisional government to be “pledged to the holding of free and unfettered elections as soon as possible.” After the war, the Soviet Union set up a puppet government in Poland and the free elections promised them never surfaced. For liberated Europe in general, the conference promised “interim governmental authorities broadly representative of all democratic elements in the population and pledged to the earliest possible establishment through free elections of governments responsive to the will of the people.” Stalin agreed to that concession thinking that the libe4rated European nations would see the Soviet Union as their saviors and create their own communist governments. When that did not happen, Stalin wiped out all opposition and set up his own governments in those areas. With regard to Germany, the conference postponed decisions on dismemberment and on future frontiers, endorsed the EAC provisions for zonal occupation. The Yalta discussions also dealt with the Orient, where the American Joint Chiefs were eager to secure from Stalin a precise commitment about entering the war. Some feared that Russia would let the United States undertake a costly invasion of Japan and then move into Manchuria and China at the last minute to reap the benefits of victory. In secret discussions with Roosevelt, Stalin agreed to declare war on Japan within two or three months after the surrender of Germany on condition that the Kurile Islands and southern Sakhalin be restored to Russia and that the commercial interest of the Soviet Union in Dairen (Luda) and its rail communications be recognized. When Roosevelt obtained the assent of Chiang Kai-shek to these measures, the Soviet Union would agree “that China shall retain full sovereignty in Manchuria” and would conclude a treaty of friendship and alliance with the Chiang Kai-shek government. After the Chinese communists under Mao Zedong gained power, Stalin was only too eager to break that agreement. He abandoned all ties to the Kai-shek government.
The Korean War also effected the American-Soviet relationship. In 1948 the Russians set up a People’s Democratic Republic in North Korea, while the Americans recognized the Republic of South Korea. In June 1949 Soviet and American forces withdrew from Korea. Kim Il-sung, the communist dictator of North Korea, came to Moscow to seek Stalin’s support for a North Korean invasion of South Korea. Stalin gave Kim his support. On June 25, 1950, North Korean troops crossed the 38th parallel in a surprise invasion. Truman wrongly saw the invasion as a Soviet effort to test the American will. If the United States did not react in Korea, he believed, the Russians would sponsor similar thrusts elsewhere; and the result might be a third world war. The Americans saw the Soviet Union as starting a war in Korea which led to the death of many innocent American soldiers and they felt hatred for the Soviets.
McCarthyism was running rampant in the United States and had a profound effect on the American-Soviet relationship. The Korean war transformed McCarthys crusade form an eccentric sideshow into a popular movement. If communist were killing American boys in Korea, why should communists be given the benefit of the doubt in the United States. People trusted the Soviets less then they ever did. The Rosenbergs were caught stealing nuclear secrets. Many influential people were accused of begin communists simply because they had different opinions. Because of McCarthyism, Congress passed the McCarran Internal Security Act which established a Subversive Activities Control Board to follow communist activities in the United States. After the jailing of many supposed Communists, how could people trust their neighbors or friends. Everyone was suspected of being a communist and many were brought up on charges. The hysteria spread like wildfire. It caught on in every town and city. The communists were against everything America was based on and since the Soviet Union was a communist country, they couldnt be trusted or ever given the benefit of the doubt.
In Conclusion, the Yalta Conference agreements, the Korean War, and McCarthyism helped to deteriorate the American-Soviet relationship in the 1950s.