After the National Assembly had adopted a constitution based on the Soviet model on May 9, 1948, elections took place on May 30, 1948, which ensured the Communist Party an absolute majority on the basis of a unified list. Czechoslovakia became a “people’s democracy” in which the Communist Party from then on had sole leadership, and the remaining parties that still existed within the National Front lost their political independence (including June 27th / September 27th, 1948, union of the Social Democrats with of the CP). Beneš refused to approve the new constitution and resigned on June 7, 1948. J. Masaryk had already divorced on March 10, 1948 under circumstances that were not completely clarified. The communists now stood next to the Prime Minister (1948–53: A. Zápotocký; 1953-63: V. Široký; 1963–68: J. Lenart) also the President (1948–53: Gottwald; 1953–57: Zápotocký; 1957–68: A. Novotný).
After adopting the Soviet planning model for the national economy and joining the Comecon (1949), according to hyperrestaurant, the ČSR (declared a “socialist” state in the new constitution in 1960 and renamed the ČSSR) became heavily dependent on the USSR. As the first secretary of the Communist Party, Gottwald pursued a Stalinist course – also using terrorist means. He used the conflict between Stalin and Tito to eliminate intra-party competitors in party and state. After show trials, prominent Communist Party members were among others. because of »Titoist and Zionist activities« (KP General Secretary R. Slánský; Foreign Minister Vladimír Clementis, * 1902, † 1952) executed or sentenced to long prison terms for “bourgeois nationalism” (G. Husák et al.). The communist leadership initiated a wave of persecution against the Catholic Church (including against the bishop and later Cardinal F. Tomášek). Agriculture was collectivized in the 1950s. With the accession to the Warsaw Pact (1955), Czechoslovakia integrated itself into the system of the Eastern Bloc led by the USSR.
For the first time since the early 1960s, the party and state leadership felt compelled to rehabilitate many victims of the political trials. Criticism within and outside the CP of the state economic policy as well as the ideological dogmatism of the party leadership – in connection with growing dissatisfaction in Slovakia – initiated a process of domestic political fermentation.
The increasingly strong reform wing in the CP Central Committee (including O. Šik, O. Černík, A. Dubček, J. Smrkovský) agreed on January 5, 1968 on Dubček as the successor to President Novotný in the post of General Secretary of the CP; General L. Svoboda became President in March 1968, and O. Černík became Prime Minister. While maintaining the sole rule of the Communist Party, the reformers’ aim was to implement approaches to liberalize and democratize society (“socialism with a human face”), although the alliance with the USSR was not called into question (Prague Spring). The economy was to be designed according to the »New Economic Model« developed by O. Šik (connection of market economy elements with state economic planning in the sense of a socialist market economy), and cultural policy (especially E. Goldstücker) to be liberalized. through increasing freedom of the press and expression. The reform policy was enthusiastically received by the population (including the »Manifesto of 2,000 Words « of June 27th). Subsequently justified by the Brezhnev Doctrine, began on the night of August 21, 1968 troops of the Warsaw Pact to invade Czechoslovakia (with the exception of Romania; two divisions of the NVA of the GDR remained on standby near the border). Subsequently, almost all reform plans were revoked (among other things, anchored in the enforced “Moscow Protocol” of August 26); only the formally initiated federalization of Czechoslovakia into a federal state of Czechs and Slovaks, d. H. the formation of a “Czech Socialist Republic” and a “Slovak Socialist Republic” (January 1, 1969) realized an important concern of the reformers. In April 1969 Dubček had the function of General Secretary of the Communist Party to Husák, in January 1970 Černík to the post of Prime Minister Resign L. Štrougal. After the signing of a new friendship treaty with the USSR (May 1970), internal party purges, mass layoffs and political processes re-established ideological lock-step with the Soviet party and state leadership (policy of “normalization”). Eventually Husák was elected President (1975; re-election 1981).
Under the influence of the “Final Act” of Helsinki (1975), Charter 77 (around 1,800 almost only Czech signatories; spokespersons: J. Hájek, V. Havel) developed in Czechoslovakia in 1980 through the Solidarność movement in Poland received further impetus (citizens’ movement). The party and state leadership tried to suppress the civil rights movement with a wave of arrests. The KPČ rejected the reform course initiated by M. S. Gorbachev in the USSR under Husák and his successor as General Secretary of the party (from December 1987), Miloš Jakeš (* 1922, † 2020); Prime Minister Štrougal resigned in October 1988return. All subsequent reform attempts were unsuccessful.