Origins of the Cold War:
Following the surrender of Nazi Germany in May 1945 near the close of World War II, the uneasy wartime alliance between the United States and Great Britain on the one hand and the Soviet Union on the other began to unravel. By 1948 the Soviets had installed left-wing governments in the countries of eastern Europe that had been liberated by the Red Army. The Americans and the British feared the permanent Soviet domination of eastern Europe and the threat of Soviet-influenced communist parties coming to power in the democracies of western Europe. The Soviets, on the other hand, were determined to maintain control of eastern Europe in order to safeguard against any possible renewed threat from Germany, and they were intent on spreading communism worldwide, largely for ideological reasons. The Cold War had solidified by 1947–48, when U.S. aid provided under the Marshall Plan to western Europe had brought those countries under American influence and the Soviets had installed openly communist regimes in eastern Europe.
