Czechoslovakia^[2] (/ˌtʃɛkoʊsloʊˈvækiə, -kə-, -slə-, -ˈvɑː-/ ^ⓘ;^[3][4] Czech and Slovak: Československo, Česko-Slovensko)^[5][6] was a landlocked state in Central Europe,^[7] created in 1918, when it declared its independence from Austria-Hungary. In 1938, after the Munich Agreement, the Sudetenland became part of Nazi Germany, while the country lost further territories to Hungary and Poland (the territories of southern Slovakia with a predominantly Hungarian population to Hungary and Zaolzie with a predominantly Polish population to Poland). Between 1939 and 1945, the state ceased to exist, as Slovakia proclaimed its independence and Carpathian Ruthenia became part of Hungary, while the German Protectorate of Bohemia and Moravia was proclaimed in the remainder of the Czech Lands. In 1939, after the outbreak of World War II, former Czechoslovak President Edvard Beneš formed a government-in-exile and sought recognition from the Allies.

After World War II, Czechoslovakia was reestablished under its pre-1938 borders, with the exception of Carpathian Ruthenia, which became part of the Ukrainian SSR (a republic of the Soviet Union). The Communist Party seized power in a coup in 1948. From 1948 to 1989, Czechoslovakia was part of the Eastern Bloc with a planned economy. Its economic status was formalized in membership of Comecon from 1949 and its defense status in the Warsaw Pact of 1955. A period of political liberalization in 1968, the Prague Spring, ended when the Soviet Union, assisted by other Warsaw Pact countries, invaded Czechoslovakia. In 1989, as Marxist–Leninist governments and communism were ending all over Central and Eastern Europe, Czechoslovaks peacefully deposed their communist government during the Velvet Revolution, which began on 17 November 1989 and ended 11 days later on 28 November when all of the top Communist leaders and Communist party itself resigned. On 31 December 1992, Czechoslovakia peacefully split into the two sovereign states of the Czech Republic and Slovakia.^[8]