"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."
The phrase had been used a year earlier, in an article on "The Year 2000" by Joseph Goebbels[1]:
"If the German people lay down their weapons, the Soviets, according to the agreement between Roosevelt, Churchill and Stalin, would occupy all of East and Southeast Europe along with the greater part of the Reich. An iron curtain would fall over this enormous territory controlled by the Soviet Union, behind which nations would be slaughtered."
Allen Dulles used the term in a speech on December 3, 1945, referring to only Germany:
It is difficult to say what is going on, but in general the Russians are acting little better than thugs. They have wiped out all the liquid assets. No food cards are issued to Germans, who are forced to travel on foot into the Russian zone, often more dead than alive. An iron curtain has descended over the fate of these people and very likely conditions are truly terrible. The promises at Yalta to the contrary, probably 8 to 10 million people are being enslaved.
It was Churchill's speech which popularized the phrase, and made it known to much of the public, however.
Although the phrase was not well received at the time, as the Cold War strengthened it gained popularity as a short-hand reference to the division of Europe. The Iron Curtain served to keep people in and information out, and the metaphor eventually enjoyed wide acceptance in the West. A variant, the Bamboo Curtain, was coined in reference to Communist China.
As the standoff between the Free World and the countries of the Iron and Bamboo curtains eased, with the West's victory in the Cold War, the term fell out of any but historical usage.