On August 20, 1968, the Soviet Union led Warsaw Pact troops in an invasion of Czechoslovakia to crack down on reformist trends in Prague. Although the Soviet Union’s action successfully halted the pace of reform in Czechoslovakia, it had unintended consequences for the unity of the communist bloc.
Before the Second World War, the nation of Czechoslovakia had been a strong democracy in Central Europe, but beginning in the mid 1930s it faced challenges from both the West and the East. In 1938, the leadership in Great Britain and Franceconceded the German right to takeover the Sudetenland in the Munich Agreement, but the Czech government condemned this German occupation of its western-most territory as a betrayal. In 1948, Czech attempts to join the U.S.-sponsored Marshall Plan to aid postwar rebuilding were thwarted by Soviet takeover and the installation of a new communist government in Prague. For the next twenty years, Czechoslovakia remained a stable state within the Soviet sphere of influence; unlike in Hungary or Poland, even the rise of de-Stalinization after 1953 did not lead to liberalization by the fundamentally conservative Czech government.
In the 1960s, however, changes in the leadership in Prague led to a series of reforms to soften or humanize the application of communist doctrines within Czech borders. The Czech economy had been slowing since the early 1960s, and cracks were emerging in the communist consensus as workers struggled against new challenges. The government responded with reforms designed to improve the economy. In early 1968, conservative leader Antonin Novotny was ousted as the head of the Communist Party of Czechoslovakia, and he was replaced by Alexander Dubcek. The Dubcek government ended censorship in early 1968, and the acquisition of this freedom resulted in a public expression of broad-based support for reform and a public sphere in which government and party policies could be debated openly. In April, the Czech Government issued a formal plan for further reforms, although it tried to liberalize within the existing framework of the Marxist-Leninist State and did not propose a revolutionary overhaul of the political and economic systems. As conflicts emerged between those calling for further reforms and conservatives alarmed by how far the liberalization process had gone, Dubcek struggled to maintain control.
Soviet leaders were concerned over these recent developments in Czechoslovakia. Recalling the 1956 uprising in Hungary, leaders in Moscow worried that if Czechoslovakia carried reforms too far, other satellite states in Eastern Europe might follow, leading to a widespread rebellion against Moscow’s leadership of the Eastern Bloc. There was also a danger that the Soviet Republics in the East, such as the Ukraine, Lithuania,Latvia, and Estonia might make their own demands for more liberal policies. After much debate, the Communist Party leadership in Moscow decided to intervene to establish a more conservative and pro-Soviet government in Prague.
The Warsaw Pact invasion of August 20–21 caught Czechoslovakia and much of the Western world by surprise. In anticipation of the invasion, the Soviet Union had moved troops from the Soviet Union, along with limited numbers of troops from Hungary, Poland, East Germany and Bulgaria into place by announcing Warsaw Pact military exercises. When these forces did invade, they swiftly took control of Prague, other major cities, and communication and transportation links. Given the escalating U.S. involvement in the conflict in Vietnam as well as past U.S. pronouncements on non-intervention in the East Bloc, the Soviets guessed correctly that the United States would condemn the invasion but refrain from intervening. Although the Soviet crackdown on Czechoslovakia was swift and successful, small-scale resistance continued throughout early 1969 while the Soviets struggled to install a stable government. Finally, in April of 1969, the Soviets forced Dubcek from power in favor of a more conservative administrator. In the years that followed, the new leadership reestablished government censorship and controls preventing freedom of movement, but it also improved economic conditions, eliminating one of the sources for revolutionary fervor. Czechoslovakia once again became a cooperative member of the Warsaw Pact.
The Soviet invasion of Czechoslovakia was significant in the sense that it delayed the splintering of Eastern European Communism and was concluded without provoking any direct intervention from the West. Repeated efforts in the UN Security Council to pass a resolution condemning the attacks met with opposition from the Soviet Union, and the effort finally died away. The invasion did, however, temporarily derail progress toward détente between the Soviet Union and the United States. The NATO allies valued the idea of a lessening of tensions, and as a result they were determined not to intervene. Still, the invasion forced U.S. President Lyndon B. Johnson to cancel a summit meeting with Soviet leader Leonid Brezhnev. Although Brezhnev knew this was the most likely outcome of the invasion, he considered maintaining Soviet control in the East Bloc a higher priority in the short-term than pursuing détente with the West. As it turned out, the progress on arms control agreements were only delayed by a few years in the aftermath of the Prague Spring.
There were also long-term consequences. After the invasion, the Soviet leadership justified the use of force in Prague under what would become known as the Brezhnev Doctrine, which stated that Moscow had the right to intervene in any country where a communist government had been threatened. This doctrine, established to justify Soviet action in Czechoslovakia, also became the primary justification for the Soviet invasion of Afghanistan in 1979, and even before that it helped to finalize the Sino-Soviet split, as Beijing feared that the Soviet Union would use the doctrine as a justification to invade or interfere with Chinese communism. Because the United States interpreted the Brezhnev Doctrine and the history of Soviet interventions in Europe as defending established territory, not expanding Soviet power, the aftermath of the Czech crisis also lent support to voices in the U.S. Congress calling for a reduction in U.S. military forces in Europe.