Left-bank Ukraine is the part of Ukraine on the left (east) bank of the Dnieper, comprising the modern-day oblasts of Chernihiv, Poltava, and Sumy as well as the eastern parts of Kyiv and Cherkasy. Since the Middle Ages, left-bank Ukraine has formed part of the Khazar Khanate, Kievan Rus, Mongol Empire, Golden Horde, Grand Duchy of Lithuania, and Kingdom of Poland. In 1663, the pro-Russian Cossack Ivan Bryukhovetsky became hetman of left-bank Ukraine while Pavlo Teteria came to rule over right-bank Ukraine under Polish suzerainty. The wars between the left and right banks resulted in "the Ruin" and ultimately Russia's assertion of control over left-bank Ukraine in 1667 and 1686. In 1721, Russia abolished the Cossack Hetmanate, and left-bank Ukraine lost its autonomy.