When World War Two ended in 1945, the alliance between the USSR, Britain, and the United States ended. The arguments between the East and the West began almost immediately. A major rivalry between non-communist and communist nations had officially begun to start the Cold War.
After the war, Germany was divided into four zones of occupation by the United States, Britain, France, and the USSR. Stalin refused to allow freely elected governments to exist in the Eastern European countries that were occupied by the Soviet Union. The new president, Harry Truman, was not willing to compromise with Stalin over this issue, and thus the Cold War grew worse. The United States wanted Eastern Europe to live by the same democratic ideals that the United States lived by, which included freedom of speech, civil liberties, and free elections. But Stalin was fearful of the possibility of governments on the USSR's western border attacking his country, since it had happened twice before, and so he was not willing to compromise on this matter either.
The West and the East were locked in a bitter stalemate. Truman cut off supplies and aid to the USSR and declared that the United States would not recognize any of the governments set up by Stalin if they were not established by the citizens' free will. The countries that were being controlled by the Soviet Union were East Germany, Romania, Bulgaria, Hungary, and Czechoslovakia, which were all under communist rule. It was the British Prime Minister, Winston Churchill that first referred to Europe being divided by an "iron curtain." .
The Cold War worsened yet again when the it appeared that Stalin was attempting to spread communism to Turkey, Greece, and China. The United States quickly passed the Truman Doctrine in an attempt to stop the spread of communism throughout Europe and Asia because the U.S. government thought that the expansion of the Soviet Union was a direct threat to the world's developing nations.