 Complete the following phrase:  In 1648, the peasants of Ukraine joined the Zaporozhian Cossacks in rebellion against PolandLithuania during the Khmelnytsky Uprising, because of the social and religious oppression they suffered under Polish rule. In 1654 the Ukrainian leader, Bohdan Khmelnytsky, offered to place Ukraine under the protection of the Russian Tsar, Aleksey I. Alekseys acceptance of this offer led to another 