In 1989, Soviet control over Eastern Europe ended when the communist regimes of the Warsaw Pact collapsed. These momentous and largely bloodless events set the stage for the end of the Cold War and ushered in a new era in international politics. Why did communism collapse relatively peacefully in Eastern Europe? Why did these changes occur in 1989, after more than four decades of communist rule? Why did this upheaval happen almost simultaneously in most of the Warsaw Pact?