The Crimean Khanate was the first Muslim territory to slip from the sultan's suzerainty, when the Treaty of Kuchuk-Kainarji forced the Sublime Porte to recognize the Tatars of the Crimea as politically independent, although the sultan remained the religious leader of the Tatars as the Muslim caliph. This was the first time the powers of the Ottoman caliph were exercised outside of Ottoman borders and ratified by a European power. The Khanate retained this nominal independence, while actually being dependent on Russia, until Catherine the Great formally annexed it in 1783, increasing Russia's power in the Black Sea area.