Which was not a critical event during the late stages of the cold war from 1968 to 1991?

The one that was not a critical event during the late stages of the cold war from 1968 to 1991 was: rise of the Solidarity trade union and political movement in Poland

The late stage of cold war filled with events that contribute to the fall of the soviet Union. Solidarity union and Poland's condition has nothing to do with it.