Czechoslovakia (Československo; from 1990 Slovak: 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 1992. From 1939 to 1945 the state did not have a de facto existence, due to its forced division and partial incorporation into Nazi Germany, but the Czech government-in-exile nevertheless continued to exist during this time period. On January 1, 1993, Czechoslovakia peacefully split into the Czech Republic and the Slovak Republic.

Czechoslovakia was founded in October 1918 as one of the successor states of Austria-Hungary at the end of World War I. It consisted of the present day territories of the Czech Republic, Slovakia and Carpathian Ruthenia. Its territory included some of the most industrialized regions of the former Austria-Hungary. It was a multiethnic state. The original ethnic composition of the new state was 51% Czechs, 16% Slovaks, 22% Germans, 5% Hungarians and 4% Rusyns or Ruthenians (trans-Carpathian Ukrainians).^[2] Many of the Germans, Hungarians, Ruthenians and Poles^[3] and also some Slovaks, felt disadvantaged in Czechoslovakia, because the political elite of the country introduced a centralized state and most of the time did not allow political autonomy for the ethnic groups. This policy, combined with increasing Nazi propaganda especially in the industrialized German speaking Sudetenland, led to increasing unrest among the non-Czech population.

The official ideology about constituent nations of the new state at the time was that there are no Czechs and Slovaks, but only one nation: Czechoslovaks (see Czechoslovakism). But not all people agreed with this ideology (mainly among Slovaks) and once a unified Czechoslovakia was restored after WWII (see dividing of the country during WWII) this idea was left behind and Czechoslovakia was a country of two nations - the Czechs and the Slovaks.