However, Russian expansion 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 in 1709 (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 the Ottoman victory at the Pruth River Campaign of 1710–1711. The subsequent Treaty of Passarowitz signed on 21 July 1718, brought a period of peace between wars. However, the Treaty also revealed that the Ottoman Empire was on the defensive and unlikely to present any further aggression in Europe.