On 20–21 August 1968, the Czechoslovak Socialist Republic was jointly invaded by four Warsaw Pact countries: the Soviet Union, the Polish People's Republic, the People's Republic of Bulgaria and the Hungarian People's Republic. The invasion stopped Alexander Dubček's Prague Spring liberalisation reforms and strengthened the authoritarian wing of the Communist Party of Czechoslovakia (KSČ).
About 250,000 Warsaw Pact troops (afterwards rising to about 500,000), supported by thousands of tanks and hundreds of aircraft, participated in the overnight operation, which was code-named Operation Danube. The Socialist Republic of Romania and the People's Republic of Albania refused to participate, while East German forces, except for a small number of specialists, were ordered by Moscow not to cross the Czechoslovak border just hours before the invasion because of fears of greater resistance if German troops were involved, due to public perception of the previous German occupation three decades earlier. 137 Czechoslovaks were killed and 500 seriously wounded during the occupation.
Public reaction to the invasion was widespread and divided, including within the communist world. Although the majority of the Warsaw Pact supported the invasion along with several other communist parties worldwide, Western nations, along with socialist countries such as Albania, Romania, Yugoslavia, and particularly the People's Republic of China (PRC) condemned the attack. Many other communist parties also lost influence, denounced the USSR, or split up or dissolved due to conflicting opinions. The invasion started a series of events that would ultimately pressure Brezhnev to establish a state of détente with U.S. President Richard Nixon in 1972 just months after the latter's historic visit to the PRC.
Background
Novotný's regime: late 1950s – early 1960s
The process of de-Stalinization in Czechoslovakia had begun under Antonín Novotný in the late 1950s and early 1960s, but had progressed more slowly than in most other states of the Eastern Bloc. Following the lead of Nikita Khrushchev, Novotný proclaimed the completion of socialism, and the new constitution, accordingly, adopted the name Czechoslovak Socialist Republic. The pace of change, however, was sluggish; the rehabilitation of Stalinist-era victims, such as those convicted in the Slánský trials, may have been considered as early as 1963, but did not take place until 1967.
In the early 1960s, Czechoslovakia underwent an economic downturn. The Soviet model of industrialization applied unsuccessfully since Czechoslovakia was already entirely industrialized before World War II, and the Soviet model mainly took into account less developed economies. Novotný's attempt at restructuring the economy, the 1965 New Economic Model, spurred increased demand for political reform as well.
1967 Writers' Congress
As the strict government eased its rules, the Union of Czechoslovak Writers cautiously began to air discontent, and in the union's gazette, , members suggested that literature should be independent of Party doctrine. In June 1967, a small fraction of the Czech writer's union sympathized with radical socialists, specifically Ludvík Vaculík, Milan Kundera, Jan Procházka, Antonín Jaroslav Liehm, Pavel Kohout and Ivan Klíma. A few months later, at a party meeting, it was decided that administrative actions against the writers who openly expressed support of reformation would be taken. Since only a small part of the union held these beliefs, the remaining members were relied upon to discipline their colleagues. Control over Literární noviny and several other publishing houses was transferred to the Ministry of Culture, and even members of the party who later became significant reformers, including Dubček, endorsed these moves.
Prague Spring
The Prague Spring (, ) was a period of political liberalization in Czechoslovakia that began on 5 January 1968, when reformist Alexander Dubček was elected First Secretary of the Communist Party of Czechoslovakia (KSČ), and continued until 21 August when the Soviet Union and other members of the Warsaw Pact invaded the country to halt the reforms.
The Prague Spring reforms were a strong attempt by Dubček 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, Dubček oversaw the decision to split into two, the Czech Republic and Slovak Republic.