The Cold War developed as differences about the shape of the postwar world created suspicion and distrust between the United States and the Soviet Union. The first such conflict occurred over Poland. Moscow demanded a government subject to Soviet influence; Washington wanted a more independent, representative government following the Western model. The Yalta Conference of February 1945 had produced a wide-ranging agreement open to different interpretations. Among its provisions was the promise of "free and unfettered" elections in Poland.
At his first meeting with Soviet Minister of Foreign Affairs Vyacheslav Molotov, Truman revealed his intention to stand firm on Polish self-determination, lecturing the Soviet diplomat about the need to carry out the Yalta accords. When Molotov protested, "I have never been talked to like that in my life," Truman retorted, "Carry out your agreements and you won't get talked to like that." Relations deteriorated from that point onward.
During the closing months of World War II, Soviet military forces occupied all of Central and Eastern Europe. Moscow used its military power to support the efforts of the communist parties in Eastern Europe and crush the democratic parties. Communist parties beholden to Moscow quickly expanded their power and influence in all countries of the region, culminating in the coup d'etat in Czechoslovakia in 1948.
Public statements defined the beginning of the Cold War. In 1946 Stalin declared that international peace was impossible "under the present capitalist development of the world economy." Winston Churchill, wartime prime minister of Great Britain, delivered a dramatic speech in Fulton, Missouri, with Truman sitting on the platform during the address. "From Stettin in the Baltic to Trieste in the Adriatic," Churchill said, "an iron curtain has descended across the Continent." Britain and the United States, he declared, had to work together to counter the Soviet threat.
Source: U.S. Department of State