A shadow has fallen upon the scenes so lately lighted by the Allied victory.... From Stettin in the Baltic to Trieste in the Adriatic an iron curtain has descended across the Continent.
Source, in full
On Soviet communism and the Cold War, in a speech at Fulton, Missouri on March 5, 1946 (complete text). Churchill did not coin the phrase "iron curtain", however; the 1920 book Through Bolshevik Russia by English suffragette Ethel Snowden contained the line "We were behind the 'iron curtain' at last!" (This fact is mentioned in the article 'Anonymous was a Woman', Yale Alumni Magazine Jan/Feb 2011).