A major rebellion of self-governed Ukrainian Cossacks inhabiting south-eastern borderlands of the Commonwealth rioted against Polish and Catholic oppression of Orthodox Ukraine in 1648, in what came to be known as the Khmelnytsky Uprising. It resulted in a Ukrainian request, under the terms of the Treaty of Pereyaslav, for protection by the Russian Tsar. In 1651, in the face of a growing threat from Poland, and forsaken by his Tatar allies, Khmelnytsky asked the Tsar to incorporate Ukraine as an autonomous duchy under Russian protection. Russian annexation of Zaporizhian Ukraine gradually supplanted Polish influence in that part of Europe.

How the tables have turned.