The Russo-Turkish War of 1787–1792 involved an unsuccessful attempt by the Ottoman Empire to regain lands lost to the Russian Empire in the course of the previous Russo-Turkish War (1768–1774). It took place concomitantly with the Austro-Turkish War (1788–1791) In 1787, the Ottomans demanded that the Russians evacuate the Crimea and give up their holdings near the Black Sea, which Russia saw as a casus belli. Russia declared war on 19 August 1787, and the Ottomans imprisoned the Russian ambassador, Yakov Bulgakov. Ottoman preparations were inadequate and the moment was ill-chosen, as Russia and Austria were now in alliance. Accordingly, the Treaty of Jassy was signed on 9 January 1792, recognizing Russia's 1783 annexation of the Crimean Khanate. Yedisan (Odessa and Ochakov) was also ceded to Russia, and the Dniester was made the Russian frontier in Europe, while the Russian Asiatic frontier—the Kuban River—remained unchanged.