Suleiman II shrewdly appointed Köprülü Fazıl Mustafa Pasha as his Grand Vizier on 25 October 1689, leading to the reconquest of Belgrade in 1690. Even so, when Russian Empire joined an alliance of European powers, the Ottomans lost the support of their Crimean vassals, who were forced to defend themselves from Russian invasion. Under Köprülü's leadership, the Ottomans halted an Austrian advance into Serbia and crushed an uprising in Macedonia and Bulgaria until Köprülü Fazıl Mustafa Pasha was killed in the Battle of Slankamen by Austrian forces.