What did churchill mean by the iron curtain

Church hill stated in a speech "A shadow has fallen across the scenes so lately lighted by Allied victory. From Stettin in the Baltic to Trieste in the Adriatic, an iron curtain has descended across the continent." We know that there was a a conference called the Potsdam Conference where the Allie powers of Great Britain, France, the U.S., and the Soviet Union agreed that  Germany was going to be divided into four occupation zones, and each country would get one. There was a political divide between West Europe and Communist Europe. Western Germany was now a capitalist country and  Eastern Germany was now a communist country. So what Church hill meant when he metaphorically said "iron curtain" he meant a political divide between Western and Eastern Europe.

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