(Spoiler Warning)
Following a period of economic and political stagnation under Brezhnev and his immediate successors, the Soviet Union decreased its intervention in Eastern Bloc politics. Mikhail Gorbachev (General Secretary from 1985) decreased adherence to the Brezhnev Doctrine, which held that if socialism were threatened in any state then other socialist governments had an obligation to intervene to preserve it, in favor of the "Sinatra Doctrine". He also initiated the policies of glasnost (openness) and perestroika (economic restructuring). A wave of Revolutions occurred throughout the Eastern Bloc in 1989