Left-bank Ukraine
Recovery of lost territories began in the mid-17th century, when the Khmelnitsky Uprising (1648–57) in Ukraine against Polish rule brought about the Treaty of Pereyaslav, concluded between Russia and the Ukrainian Cossacks. According to the treaty, Russia granted protection to the Cossacks state in Left-bank Ukraine, formerly under Polish control. This triggered a prolonged Russo-Polish War (1654-1667), which ended with the Treaty of Andrusovo, where Poland accepted the loss of Left-bank Ukraine, Kiev and Smolensk.