The first major Russo-Turkish War (1768–1774) began after Turkey demanded that Russia’s ruler, Catherine II the Great, abstain from interfering in Poland’s internal affairs. The Russians went on to win impressive victories over the Turks. They captured Azov, the Crimea, and Bessarabia, and under Field Marshal Pyotr Rumyantsev they overran Moldavia and also defeated the Turks in Bulgaria. The Turks were compelled to seek peace, which was concluded in the Treaty of Küçük Kaynarca. This treaty made the Crimean khanate independent of the Turkish sultan advanced the Russian frontier. Russia was now in a much stronger position to expand, and in 1783 Catherine annexed the Crimean Peninsula outright.