Which began in 1980 in Poland

Checz had it even earlier.

Hungary '56. Let's not get into a contest here.

We could probably go back to the 50s and all the events all around the eastern block during those times but that was not the point. Just that the events around 1980 (Gdansk .pl, Velvet .cz.sk) started the domino effect which led to dropping the Berlin Wall and eventually failure of the USSR. No contest here.

To be pedantic, it was the economic inefficiencies of the communist bloc that started everything. Events were just inevitablities.