The Prague Spring (Czech: Prask jaro, Slovak: Prask jar) was a period of political liberalization and mass protest in

the Czechoslovak Socialist Republic. It began on 5 January 1968, when reformist Alexander Dubek was elected First Secretary of the Communist Party of Czechoslovakia (KS), and continued until 21 August 1968, when the Soviet Union and other Warsaw Pact members invaded the country to suppress the reforms.

The Prague Spring reforms were a strong attempt by Dubek to grant additional rights to the citizens of Czechoslovakia in an act of partial decentralization of the economy and democratization. The freedoms granted included a loosening of restrictions on the media, speech and travel. After national discussion of dividing the country into a federation of three republics, Bohemia, Moravia-Silesia and Slovakia, Dubek oversaw the decision to split into two, the Czech Socialist Republic and Slovak Socialist Republic. This dual federation was the only formal change that survived the invasion.

The reforms, especially the decentralization of administrative authority, were not received well by the Soviets, who, after failed negotiations, sent half a million Warsaw Pact troops and tanks to occupy the country. The New York Times cited reports of 650,000 men equipped with the most modern and sophisticated weapons in the Soviet military catalogue. A massive wave of emigration swept the nation. Resistance was mounted throughout the country, involving attempted fraternization, sabotage of street signs, defiance of curfews, etc. While the Soviet military had predicted that it would take four days to subdue the country, the resistance held out for eight months until diplomatic maneuvers finally circumvented it. It became a high-profile example of civilian-based defense; there were sporadic acts of violence and several protest suicides by self-immolation (the most famous being that of Jan Palach), but no military resistance. Czechoslovakia remained controlled by the Soviet Union until 1989, when the Velvet Revolution peacefully ended the communist regime; the last Soviet troops left the country in 1991.

After the invasion, Czechoslovakia entered a period known as normalization (Czech: normalizace, Slovak: normalizcia), in which new leaders attempted to restore the political and economic values that had prevailed before Dubek gained control of the KS. Gustv Husk, who replaced Dubek as First Secretary and also became President, reversed almost all of the reforms. The Prague Spring inspired music and literature including the work of Vclav Havel, Karel Husa, Karel Kryl and Milan Kundera's novel The Unbearable Lightness of Being.

The Warsaw Treaty Organization (WTO), officially the Treaty of Friendship, Cooperation and Mutual Assistance, commonly known as the Warsaw Pact (WP), was a collective defense treaty signed in Warsaw, Poland, between the Soviet Union and seven other Eastern Bloc socialist republics of Central and Eastern Europe in May 1955, during the Cold War. The Warsaw Pact was the military complement to the Council for Mutual Economic Assistance (CoMEcon), the regional economic organization for the socialist states of Central and Eastern Europe. The Warsaw Pact was created in reaction to the integration of West Germany into NATO in 1955 as per the London and Paris Conferences of 1954.Dominated by the Soviet Union, the Warsaw Pact was established as a balance of power or counterweight to NATO. There was no direct military confrontation between the two organisations; instead, the conflict was fought on an ideological basis and in proxy wars. Both NATO and the Warsaw Pact led to the expansion of military forces and their integration into the respective blocs. Its largest military engagement was the Warsaw Pact invasion of Czechoslovakia in August 1968 (with the participation of all Pact nations except Albania and Romania), which, in part, resulted in Albania withdrawing from the Pact less than a month later. The Pact began to unravel with the spread of the Revolutions of 1989 through the Eastern Bloc, beginning with the Solidarity movement in Poland, its electoral success in June 1989 and the Pan-European Picnic in August 1989.East Germany withdrew from the Pact following German reunification in 1990. On 25 February 1991, at a meeting in Hungary, the Pact was declared at an end by the defense and foreign ministers of the six remaining member states. The USSR itself was dissolved in December 1991, although most of the former Soviet republics formed the Collective Security Treaty Organization shortly thereafter. In the following 20 years, the Warsaw Pact countries outside the USSR each joined NATO (East Germany through its reunification with West Germany; and the Czech Republic and Slovakia as separate countries), as did the Baltic states which had been part of the Soviet Union.