The Cold War was mainly a conflict for world supremacy. After the World War II, only two world superpowers stood up, each with its own political and economical ideology, and strategic interest, and a conflict between them was unavoidable. This competition was the fuel of the Cold War and since none of the parts was willing to give up and take defeat, the conflict lasted as long as the two superpowers existed. As the Soviet Union began to assert its control in Eastern Europe, the expansion of communism became the main concern of the United States. The US Government feared that, as the Soviet power was growing, this could generate revolution in the Western European countries and the movement would eventually reach the American soil. The danger seemed even higher as communist parties already existed in the Western hemisphere. In the same time, to keep total control, the communist states were isolated from the rest of the world (from where the term of Iron Curtain). This isolation increased the worry of the US government.
The Cold War was rooted in the fear of communism. To avoid this possibility, the United States took measures to block the expansion of the communist ideology. This odd sort of war was opened not by a cannon shot, but by a well known discourse. The speech delivered by Winston Churchill in 1946 in the town of Fulton, Missouri, drew attention to the danger that Western democracies were on the verge of being swallowed up by communism, and suggested a close Anglo-American alliance to defend their interests. The blackmail of the atomic bomb could not serve anymore at that time especially since the Soviets already had this weapon. And since the offensive was not recommended, the chosen alternative was the defensive. In 1947 President Truman, concerned about the security of Greece and Turkey, announced the Truman Doctrine. The U.S. agreed to support the free nations’ fight against the attempts of subjugation. This meant that the U.S. would act to restrain the expansion of communism.
Constantiniu, Florin. From the hot to the cold war. Bucharest, Romania: Corint, 1998, 111-120
Henretta, James A, and David Brody. “America: A Concise History, Volume II: Since 1877.” 4th ed., Boston: Bedford/ St. Martin’s, 2010, 766-775