The Russo-Turkish War of 1735–1739 between Russia and the Ottoman Empire was caused by the Ottoman Empire's war with Persia and continuing raids by the Crimean Tatars. The war also represented Russia's continuing struggle for access to the Black Sea. In 1737, the Habsburg monarchy joined the war on Russia's side, known in historiography as the Austro-Turkish War of 1737–1739. Russian diplomacy before the war By the outbreak of the Russo-Turkish war, Russia had managed to secure a favorable international situation by signing treaties with the Persian Empire in 1732–1735 (which was at war with the Ottoman Empire in 1730–1735) and supporting the accession to the Polish throne of Augustus III in 1735 instead of the French protégé Stanislaw Leszczynski, nominated by pro-Turkish France. Austria had been Russia's ally since 1726. The course of the war in 1735–1738 The casus belli were the raids of the Crimean Tatars on Cossack Hetmanate in the end of 1735 and the Crimean Khan's military campaign in the Caucasus. In 1736, the Russian commanders envisioned the seizure of Azov and the Crimean Peninsula. In 1735, on the eve of the war, the Russians made peace with Persia, giving back all the remaining territory conquered during the Russo-Persian War (Treaty of Ganja). On 20 May 1736, the Russian Dnieper Army (62,000 men) under the command of Field Marshal Burkhard Christoph von Münnich took by storm the Crimean fortifications at Perekop and occupied Bakhchysarai on June 17. Crimean khans failed to defend their territory and repel the invasion, and in 1736, 1737 and 1738 Russian expeditionary armies broke through their defensive positions, pushing deep into the Crimean peninsula, driving the Tatar noblemen into the hills and forcing Khan Fet’ih Girey to take refuge at sea. They burned Gozlev, Karasubazar, the khan's palace in the Crimean capital, Bakhchysarai, and captured the Ottoman fortress at Azov. Khans Kaplan Girey and Fat’ih Girey were deposed by the Ottoman sultan for their incompetence. However, 1737 to 1739 were notable plague years and all sides of the conflict were crippled by disease and unsanitary conditions. Despite his success and a string of battlefield victories, the outbreak of an epidemic coupled with short supplies forced Münnich to retreat to Ukraine. On 19 June, the Russian Don Army (28,000 men) under the command of General Peter Lacy with the support from the Don Flotilla under the command of Vice Admiral Peter Bredahl seized