A well-organized liberation movement in the Baltic countries was a major headache for Moscow, and not only because the Soviet Union did not want to repeal the secret protocols between Nazi Germany and Soviet Union, but also because the movement had spread in a more virulent form to other republics all over the Soviet Union.
The Soviets called it "the Baltic disease."
Moscow understood that if the Baltics go, so goes the Soviet Union.
On August 23, 1989, more than two months before the fall of the Berlin Wall, something truly remarkable and rarely seen in the long history of collective social behavior happened. To mark the 50th anniversary of the Molotov-Ribbentrop Pact and protest the illegal Soviet occupation, two million people from Lithuania, Latvia and Estonia joined hands in a human chain spinning 600 km from Vilnius to Riga to Tallinn. They held hands, carried signs and sang national songs. The demonstration, during which words ‘freedom’ and ‘independence’ were passed on along the human chain, was organized to draw the world’s attention to the common fate that the three Baltic nations had suffered.