Answer: The Soviets responded with military force and crushed the revolts.
Here are some examples:
- June, 1953, East Germany ... Construction workers in East Berlin began the protests, demanding an increase in work hours and calling for a general strike. The call to strike was broadcast over Radio in the American Sector (RIAS) in West Berlin and heard throughout East Germany. Over a million workers in 700 cities and towns heeded the call to strike on June 17, 1953. The Soviet Union responded swiftly and harshly, declaring a state of emergency and sending in tanks to larger cities where protests were occurring.
- October/November, 1956 - Hungary ... Protesters took to the streets in Hungary in October, 1956, demanding freedom from Soviet domination and more democratic political processes. Soviet domination and oppression continued relentlessly, as the USSR sent tanks and troops and crushed the Hungarian Uprising. Thousands of Hungarians were killed or wounded and over 200,000 fled the country.
- January-August, 1968 - Czechoslovakia ... In January, 1968, the new leader in Czechoslovakia, Alexander Dubcek, launched the "Prague Spring" (as it became known). He sought to give communism "a human face," as he termed it, introducing many political and economic reforms. By August, the USSR responded by sending in 600,000 troops, and again those Soviet tanks. The revolution was put down.
These were all precursors of later revolutions. By 1989, the communist bloc countries of Eastern Europe could no longer sustain their governments and the USSR itself was weakening.