Nonetheless , at the Potsdam Conference , the Allies assigned parts of Poland , Finland , Romania , Germany , and the Balkans to Soviet control or influence . In return , Stalin promised the Western Allies that he would allow those territories the right to national self-determination . Despite Soviet cooperation during the war , these concessions left many in the West uneasy . In particular , Churchill feared that the United States might return to its pre-war isolationism , leaving the exhausted European states unable to resist Soviet demands . ( President Franklin D. Roosevelt had announced at Yalta that after the defeat of Germany , U.S. forces would withdraw from Europe within two years . ) Winston Churchill 's " Sinews of Peace " address of 5 March 1946 , at Westminster College in Fulton , Missouri , used the term " iron curtain " in the context of Soviet-dominated Eastern Europe : From Stettin in the Baltic to Trieste in the Adriatic an iron curtain has descended across the Continent . Behind that line lie all the capitals of the ancient states of Central and Eastern Europe . Warsaw , Berlin , Prague , Vienna , Budapest , Belgrade , Bucharest and Sofia ; all these famous cities and the populations around them lie in what I must call the Soviet sphere , and all are subject , in one form or another , not only to Soviet influence but to a very high and in some cases increasing measure of control from Moscow . Much of the Western public still regarded the Soviet Union as a close ally in the context of the recent defeat of Nazi Germany and of Imperial Japan . Although not well received at the time , the phrase '' iron curtain '' gained popularity as a shorthand reference to the division of Europe as the Cold War strengthened . The Iron Curtain served to keep people in and information out , and people throughout the West eventually came to accept and use the metaphor
Potsdam Conference
Potsdam Conference
Iron Curtain