The Russo-Turkish War 1722-23
The Russo-Turkish War was the result of the Russian effort to gain Azov and Crimea as a first step towards dominating the Black Sea.
In several successful raids the Russians broke the resistance of the Crimean Khanate, crossed the Dniester into Moldavia and in 1739 marched as far as the Moldavian capital, which they captured.
The Austrian Habsburg Monarchy entered the war in 1737 on the Russian side to get its share, but was forced to make peace with the Ottomans at the separate Treaty of Belgrade, surrendering Northern Serbia and Northern Bosnia, and allowing the Ottomans to resist the Russian push toward Istanbul.
In return, the Sultan acknowledged the Habsburg Emperor as the official protector of all Ottoman Christian subjects.
The Austrian pullout, and the threat of a Swedish invasion, forced Russia to accept peace, giving up its claims to Crimea and Moldavia, being allowed to build a port at Azov but not to build fortifications there or have any fleet in the Black Sea.