The casus belli were the raids of the Crimean Tatars on Cossack Hetmanate (Ukraine) in the end of 1735 and the Crimean khan's military campaign in the Caucasus.The war also represented Russia's continuing struggle for access to the Black Sea. In July 1737, Austria entered the war against the Ottoman Empire, but was defeated a number of times, amongst others in the Battle of Banja Luka on 4 August 1737, Battle of Grocka at 18, 21–22 July 1739, and then lost Belgrade after an Ottoman siege from 18 July to September 1739. With the imminent threat of a Swedish invasion, and Ottoman alliances with Prussia, Poland and Sweden, forced Russia to sign the Treaty of Niš with Turkey on 29 September, which ended the war. The peace treaty granted Azov to Russia and consolidated Russia's control over the Zaporizhia. For Austria, the war proved a stunning defeat. The Russian forces were much more successful on the field, but they lost tens of thousands to disease. The loss and desertion figures for the Ottomans are impossible to estimate.