On 20–21 August 1968, the Czechoslovak Socialist Republic was jointly invaded by four fellow 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 (rising afterwards 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. 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 Romania, and particularly the People's Republic of China and People's Socialist Republic of Albania condemned the attack. Many other communist parties also lost influence, denounced the USSR, split up or dissolved due to conflicting opinions. The invasion started a series of events that would ultimately pressure General Secretary Leonid 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.Williams (1997), p. 170 Following the lead of Nikita Khrushchev, Novotný proclaimed the completion of socialism, and the new constitution,Williams (1997), p. 7 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, Literární noviny, 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.Czech radio broadcasts 18–20 August 1968

Brezhnev's government

Leonid Brezhnev and the leadership of the Warsaw Pact countries were worried that the unfolding liberalizations in Czechoslovakia, including the ending of censorship and political surveillance by the secret police, would be detrimental to their interests. The first such fear was that Czechoslovakia would defect from the Eastern Bloc, injuring the Soviet Union's position in a possible Third World War with the North Atlantic Treaty Organization (NATO). Not only would the loss result in a lack of strategic depth for the USSR,Karen Dawisha (1981). "The 1968 Invasion of Czechoslovakia: Causes, Consequences, and Lessons for the Future" in Soviet-East European Dilemmas: Coercion, Competition, and Consent ed. Karen Dawisha and Philip Hanson. New York: Homs and Meier Publishers Inc. but it would also mean that it could not tap Czechoslovakia's industrial base in the event of war.Jiri Valenta, Soviet Intervention in Czechoslovakia, 1968: Anatomy of a Decision (Baltimore, MD: Johns Hopkins University Press, 1979) 3 Czechoslovak leaders had no intention of leaving the Warsaw Pact, but Moscow felt it could not be certain exactly of Prague's intentions. However, the Soviet government was initially hesitant to approve an invasion, due to Czechoslovakia's continued loyalty to the Warsaw Pact and the Soviet Union's recent diplomatic gains with the West as détente began.

Other fears included the spread of liberalization and unrest elsewhere in Eastern Europe. The Warsaw Pact countries feared that if the Prague Spring reforms went unchecked, then those ideals might very well spread to Poland and East Germany, upsetting the status quo there as well. Within the Soviet Union, nationalism in the republics of Estonia, Latvia, Lithuania, and Ukraine was already causing problems for Moscow, and many were worried that events in Prague might exacerbate those problems.Jiri Valenta, "From Prague to Kabul," International Security 5, (1980), 117

According to documents from the Ukrainian Archives, compiled by Mark Kramer, KGB chairman Yuri Andropov and Communist Party of Ukraine leaders Petro Shelest and Nikolai Podgorny were the most vehement proponents of military intervention.Mark Kramer. Ukraine and the Soviet-Czechoslovak Crisis of 1968 (part 2) . New Evidence from the Ukrainian Archives. Cold War International History Project Bulletin, Issue 14/15. 2004. pp. 273–275. The other version says that the initiative for the invasion came originally from Poland as the Polish First Secretary Władysław Gomułka and later his collaborator, East German First Secretary Walter Ulbricht, pressured Brezhnev to agree on the Warsaw Letter and on ensued military involvement.

Gomułka accused Brezhnev of being blind and looking at the situation in Czechoslovakia with too much of emotion. Ulbricht, in turn, insisted upon the necessity to enact military action in Czechoslovakia while Brezhnev was still doubting. Poland's foreign policy on the issue is still unknown. The deliberation that took place in Warsaw meeting, resulted in a majority consensus rather than unanimity. According to Soviet politician Konstantin Katushev, "our allies were even more worried than we were by what was going on in Prague. Gomulka, Ulbricht, Bulgarian First Secretary Todor Zhivkov, even Hungarian First Secretary János Kádár, all assessed the Prague Spring very negatively."

The "hardline" faction among Eastern bloc leaders was represented by Ulbricht and Gomułka. Ulbricht, worried about his own power and the stability of the East German state, disavowed the reforms vehemently early on, as evidenced in his letters by the fact that he was concerned and fearful about “the effects of the cancer" of Dubcekism in his own country.”Jiri Valenta, Soviet Intervention in Czechoslovakia, 1968: Anatomy of a Decision (Baltimore: Johns Hopkins University Press, 1991). He continued to emphasize that Dubček's reforms were "antirevolutionary" and a mockery of the Marxist–Leninist ideology he espoused, and as a result emphatically called out for military intervention at the Warsaw Conference in July 1968.Mark Stolarik, The Prague Spring and the Warsaw Pact Invasion of Czechoslovakia, 1968: Forty Years Later (Mundelein, Ill: Bolchazy-Carducci Publishers, 2010).

Part of Czechoslovakia bordered Austria and West Germany, which were on the other side of the Iron Curtain. This meant both that foreign agents could slip into Czechoslovakia and into any member of the Eastern bloc and that defectors could slip out to the West.Valenta (Fn. 7) 17 The final concern emerged directly from the lack of censorship; writers whose work had been censored in the Soviet Union could simply go to Prague or Bratislava and air their grievances there, circumventing the Soviet Union's censorship.

Dubček's rise to power As President Antonín Novotný was losing support, Alexander Dubček, First Secretary of the regional Communist Party of Slovakia, and economist Ota Šik challenged him at a meeting of the Central Committee. Novotný then invited Soviet premier Leonid Brezhnev to Prague that December, seeking support; but Brezhnev was surprised at the extent of the opposition to Novotný and thus supported his removal as Czechoslovakia's leader. Dubček replaced Novotný as First Secretary on 5 January 1968. On 22 March 1968, Novotný resigned his presidency and was replaced by Ludvík Svoboda, who later gave consent to the reforms.

When the KSČ Presidium member Josef Smrkovský was interviewed in a Rudé Právo article, entitled "What Lies Ahead", he insisted that Dubček's appointment at the January Plenum would further the goals of socialism and maintain the working class nature of the Communist Party.

Socialism with a human face

On the 20th anniversary of Czechoslovakia's "Victorious February", Dubček delivered a speech explaining the need for change following the triumph of socialism. He emphasized the need to "enforce the leading role of the party more effectively" and acknowledged that, despite Klement Gottwald's urgings for better relations with society, the Party had too often made heavy-handed rulings on trivial issues. Dubček declared the party's mission was "to build an advanced socialist society on sound economic foundations ... a socialism that corresponds to the historical democratic traditions of Czechoslovakia, in accordance with the experience of other communist parties ..."Navrátil (2006), pp. 52–54

In April, Dubček launched an "Action Programme" of liberalizations, which included increasing freedom of the press, freedom of speech and freedom of movement, with economic emphasis on consumer goods and the possibility of a multiparty government. The programme was based on the view that "Socialism cannot mean only liberation of the working people from the domination of exploiting class relations, but must make more provisions for a fuller life of the personality than any bourgeois democracy."Ello (1968), pp. 32, 54