Churchill's "Iron Curtain" speech

The Iron Curtain was the political and physical boundary that divided Europe from the end of World War II in 1945 until the end of the Cold War in 1990/1991. East of the Iron Curtain were many small states aligned with the Soviet Union, in 1955 formally allied by the Warsaw Pact. Many nations to the west of this geopolitical divide were (and are) NATO members. Over time these economic and military alliances developed into broader, more entrenched, cultural barriers; widespread distrust on both sides deepened. Initially, the term "Iron Curtain" was a literal description of physical barriers such as razor wire, fences, fortified walls, minefields, and watchtowers along the western border of the Eastern Bloc. The term later took on a broader, metaphoric meaning perceived as a generalized "differentness" of ideology, economy, government, and way of life that emerged when the Cold War severed earlier cultural connections between European populations.

The term's origin is often attributed to the Fulton Speech delivered by Winston Churchill on 5 March 1946 in Fulton, Missouri, where he said: "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." In fact, the phrase was originally used by Queen Elisabeth of Belgium in 1914, when she described an "Iron Curtain" descending between her people and Germany.

The states/nations to the east of the Iron Curtain were the three Baltic states (Estonia, Latvia, and Lithuania), Poland, East Germany, Czechoslovakia, Hungary, Romania, Bulgaria, Albania and the USSR. The Red Army had invaded and annexed the Baltic states in 1940 on Stalin's orders. Republics of the USSR were the Russian SFSR, Byelorussian SSR, Ukrainian SSR, Moldavian SSR, Latvian SSR, Lithuanian SSR, Estonian SSR, Armenian SSR, Azerbaijan SSR, Georgian SSR, Uzbek SSR, Kirghiz SSR, Tajik SSR, Turkmen SSR, and Kazakh SSR.

Events that demolished the Iron Curtain started with the fall of communism in Poland,

Hungary, East Germany, Bulgaria, Czechoslovakia and Romania. East Germany reunited with West Germany on 3 October 1990. The USSR dissolved itself in December 1991. Czechoslovakia dissolved in 1992. Due to the decreased human activity around the physical border during the Cold War, natural biotopes were formed, now the European Green Belt. With the exception of the Kars-Gyumri railway crossing which operated during the Soviet Era, the Turkish–Armenian border has remained closed since the 1920s and is sometimes described as the Iron Curtain's last vestige.