Dnieper Ukraine
The Ottoman Empire, which had previously been involved in Ukrainian affairs by Bohdan Khmelnytsky, now under the leadership of Sultan Mehmed IV and his Grand Vizier Ahmed Köprülü, interpreted the Ukrainian disorder as an opportunity for its own expansion in the region. The Commonwealth's friend, Tatar Khan Mehmed IV Giray was removed in 1666 and Petro Doroshenko, the Cossack hetman of right-bank Ukraine, seeking the threatened by the Polish-Russian negotiations unity of Ukraine, accepted Ottoman suzerainty. In fall of 1666, the Tatars eliminated the Commonwealth military units present in Dnieper Ukraine, but the 1667 sejm reduced the country's army to 20,000 nevertheless.