History of Disintegration in Eastern Europe

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The collapse of the USSR:

The decline of Soviet power began in the late 1980s with protests in the Eastern Bloc as well as in Soviet republics and the Soviet exit from Afghanistan.
The Soviet Union sent troops to Afghanistan in 1979 to install a communist regime and after 10 years of fighting the Mujahideen, who were backed by the U.S., Pakistan and Saudi Arabia, the Soviets had to pull back in February 1989.
Within months, Soviet-backed communist regimes in Eastern Europe started collapsing, practically bringing the Cold War to an end.
It started in Poland, which hosted the headquarters of the Soviet-led Warsaw Pact security alliance.
Protests spread to Hungary, East Germany, Bulgaria, Czechoslovakia and Romania.
In June 1989, the anti-communist Solidarity movement, led by Lech Wałęsa, won an overwhelming victory in a partially free election in Poland, leading to the peaceful fall of communist rule.
It triggered a chain reaction across the Eastern Bloc.
In November 1989, the Berlin Wall that had separated the capitalist West Berlin and the communist east, fell, leading to the German reunification a year later.