Leonid Brezhnev before the Fifth Congress of the Polish United Workers’ Party on November 13, 1968:
The crackdown of the Hungarian uprising in 1956 had for some time crushed all hopes of reforming Communist regimes. But by the mid-1960s the reformist spirit was sparked again, this time in Czechoslovakia. The new party leader Alexander Dubcek unleashed economic (less state control, more market) and political (more open debate in the party and in the media) reforms. These reforms moving towards “socialism with a human face” produced the “Prague Spring.” The Kremlin and the Warsaw Pact allies feared a spill-over of these reforms into their countries. They put a lot of pressure on the Dubcek regime to take back the reforms.
When he failed to do so, an invasion force from five Warsaw Pact countries invaded Czechoslovakia on August 21, 1968. This massive military force stopped the reforms and re-imposed orthodox Communist Party control. The United States and NATO took no action in response to the Warsaw Pact intervention. The invasion was retroactively justified by the “Brezhnev Doctrine” (named after the Politburo chief Leonid Brezhnev), which proclaimed a de facto limited sovereignty of the Kremlin’s satellite regimes.
In the center of Prague on St. Wencelav Square, thousands of civilian protesters demonstrate their agony over the Warsaw pact invasion of their country to stamp out the reforms of the Prague Spring.