Answer: "Glasnost and Perestroika," the liberalization of a rigid communist system.
Explanation:
Reforms of the system called "Perestroika (Reorganization) and Glasnost (Public Information)" were introduced by Soviet leader Mikhail Gorbachev.With these principles, Gorbachev did not intend to cause the system to collapse but wanted to reform it from the top of the pyramid.Gorbachev allowed some communist countries to experiment with reforms but also warned about the importance of the party.
However, reforms have taken more and more momentum. Communism is a closed political system, and these reforms have just implied the opposite. Soon no communists will come to power in Poland after forty years. Communism in Europe was in huge trouble. Fundamental changes were necessary. Thus, Glasnost and Perestroika accelerated the collapse of the communist system in Europe.