Czechoslovakia became fully communist in February 1948 and was a member of both the Warsaw Pact and the Council for Mutual Economic Assistance (COMECON, the Soviet counterpart to the Marshall Plan). As such, it had very close ties to the Soviet Union, politically as well as economically.
During the 1960s, following the ascension of Nikita Khrushchev to the position of premier, the Soviet Union’s relations with its satellite nations in eastern Europe softened, leading to greater flexibility in their political and economic policies. One of the greatest tests of how far this new flexibility would stretch was initiated by Alexander Dubcek, the political head of Czechoslovakia.
Another factor influencing these events was the spread of student movements across the continent of Europe, particularly in West Germany, Italy, and France. In 1967 these student movements spilled over into Czechoslovakia and dovetailed with increasing intellectual dissent among some of the Communist Party membership.
Internally there were deep-rooted fissures in the unity of the state. The Communist Party of Czechoslovakia was fragmented, stemming from the political trials of the 1950s, which revolved around questioning party comrades’ commitment to Stalinism.
As the party discussed economic changes, two unforeseen developments occurred. Some among the party began to call for relaxed censorship, and Slovak nationalists began to demand a greater share of political power.
These events led to the resignation of president and first secretary of the Party Antoni´n Novotný. Later in March Ludwig Svoboda assumed the post of president, due to legislation that mandated that these two positions be separated, as Novotný’s criticism of early reforms foundered.
Dubcek then implemented a series of radical reforms collectively known as the Action Program. These reforms allowed freedom of expression rather than strict censorship; promoted open, public discussion of important national issues; democratized the KSC; provided amnesty for all political prisoners for the first time in 20 years; encouraged greater economic freedom; allowed noncommunists to assume high-ranking government positions; and opened investigations into the political trials of the 1950s.
These reforms became known as the Prague Spring, harkening back to the 1956 attempts of Hungarian Imre Nagy to redefine the role of the Communist Party within the state. The reforms were officially approved by the government on April 5, 1968; however, a rift between liberal communists, who supported Dubcek, and hard-line communists, who supported Moscow’s policy, became more clearly defined.
Czechoslovak intellectuals responded by calling for long-term commitment, through the publication of a manifesto, which became known as the "Two Thousand Words". The Soviet reaction to this manifesto was swift and critical, which pushed Dubcek’s government to officially condemn its ideas in order to preserve its delicate relations with the Soviet Union.
Czechoslovakia’s Warsaw Pact neighbors saw this blossoming of freedoms, particularly the "Two Thousand Words", as a potential danger that threatened to spill over the border and raise public protest within their own nations.
However, initially through a series of meetings, it seemed as if the Warsaw Pact nations would allow these experiments to continue. In late July and early August of 1968, at the border village of Cierna nad Tisou, the political leadership of Czechoslovakia and the Soviet Union met to discuss these developments.
This meeting was followed by an additional conference, adding delegates from Bulgaria, East Germany, Hungary, and Poland, which convened at Bratislava on August 3. These meetings ended with promises of renewed friendship and commitment to socialism; yet Warsaw Pact troops began to mass along the border with Czechoslovakia.
Suddenly, during the night of August 20–21, 1968, the Soviet Union and other Warsaw Pact nations sent 500,000 troops across the border, while Soviet aircraft landed special forces directly in the capital city of Prague, seizing control of key transportation junctures and communication networks.
The native population responded with defiance, seen in public protests and demonstrations, and more than 80,000 political refugees streamed into the West, seeking asylum. The Soviets suffered minor military losses of 96 killed and 87 wounded; only 11 of those killed died due to direct confrontation with Czechoslovak citizens.
By mid-September, Warsaw Pact troops had killed more than 80 Czechoslovakian citizens, seriously wounded another 266, and lightly wounded an additional 436. The Soviet Union was unable to establish an alternative government, and initially kept Alexander Dubcek in his post.
Dubcek gave in to Soviet demands and repealed his progressive policies. In April 1969 the Soviets installed Gustav Husák as Dubcek’s replacement, and Husák then carried out "normalization" efforts and presided over a purge of the KSC.
Prague Spring marked the end to the flexibility of Khrushchev, but it also stood as a harbinger of Mikhail Gorbachev’s policies of glasnost and perestroika of the 1980s. Under the leadership of Leonid Brezhnev this autonomy would cease to exist, a trend that lasted until the time of Gorbachev and the early rumblings of the revolutions of 1989.
Brezhnev made this policy shift clear; essentially the "Brezhnev Doctrine" meant that although the Soviet Union would not normally interfere in the affairs of its satellite states, if the system of socialism itself was under direct threat the Soviet Union would help any communist regime maintain power against the threat of overthrow.