Czechoslovakia, or Czecho-Slovakia (/ˌtʃɛkoʊsloʊˈvækiə, -kə-, -slə-, -ˈvɑː-/; Czech and Slovak: Československo, Česko-Slovensko), was a sovereign state in Central Europe that existed from October 1918, when it declared its independence from the Austro-Hungarian Empire, until its peaceful dissolution into the Czech Republic and Slovakia on 1 January 1993. From 1939 to 1945, following its forced division and partial incorporation into Nazi Germany, the state did not de facto exist but its government-in-exile continued to operate. From 1948 to 1990, Czechoslovakia was part of the Eastern Bloc with a command economy. Its economic status was formalized in membership of Comecon from 1949 and its defense status in the Warsaw Pact of May 1955. A period of political liberalization in 1968, known as the Prague Spring, was forcibly ended when the Soviet Union, assisted by several other Warsaw Pact countries, invaded Czechoslovakia. In 1989, as Marxist–Leninist governments and socialism were ending all over Europe, Czechoslovaks peacefully deposed their government in the Velvet Revolution; state price controls were removed after a period of preparation. In 1993, Czechoslovakia split into the two sovereign states of the Czech Republic and Slovakia.