Czechoslovakia (Prague Spring)

The USSR thought they would lose control as Dubcek launched reforms known as the “Prague Spring”. Dubcek planned to modernise communism with “Socialism with a human face” by introducing free expression and ending rule of terror by secret police. There was talk of setting up the Social democratic Party as a rival to the Communists. The USSR thought this would threaten their control of Eastern Europe.
Dubcek assured Brezhnev that he did not want to leave the Warsaw Pact but Brezhnev knew that if control was lessened in one country others would follow. This would undermine Soviet control. The USSR feared that Czechoslovakia would ally with Yugoslavia and Romania.
Czechoslovakia was too important to the security of the Soviet Union as it had borders with West Germany and the USSR.

Brezhnev was the new Soviet leader and he was just as determined as previous leaders to maintain Soviet control of eastern Europe and he felt this control was being threatened.