Aside from the loss of the Banat and the temporary loss of Belgrade (1717–1739), the Ottoman border on the Danube and Sava remained stable during the eighteenth century. Russian expansion, however, presented a large and growing threat. Accordingly, King Charles XII of Sweden was welcomed as an ally in the Ottoman Empire following his defeat by the Russians at the Battle of Poltava of 1709 in central Ukraine (part of the Great Northern War of 1700–1721). Charles XII persuaded the Ottoman Sultan Ahmed III to declare war on Russia, which resulted in an Ottoman victory in the Pruth River Campaign of 1710–1711, in Moldavia.