Westphalia to be Catholic. Osnabrück was divided almost equally between Catholicism and Protestantism. Parts of Westphalia came under Brandenburg-Prussian control during the 17th and 18th centuries, but most of it remained divided by duchies and other areas of feudal power. The Peace of Westphalia of 1648, signed in Münster and Osnabrück, ended the Thirty Years' War. The concept of nation-state sovereignty resulting from the treaty became known as "Westphalian sovereignty". After the defeat of the Prussian Army by the French at the Battle of Jena–Auerstedt, the Treaty of Tilsit in 1807 made the easternmost portion of today's Westphalia part of the
Treaty of Belgrade the autonomy of Kingdom of Serbia which had existed since 1718. This territory would await the next Habsburg-Ottoman war to be temporarily again included into the Habsburg Monarchy in 1788 with the help of Koča Anđelković. Treaty of Belgrade The Treaty of Belgrade, known as the Belgrade peace was the peace treaty signed on September 18, 1739 in Belgrade, Habsburg Kingdom of Serbia (today Serbia), by the Ottoman Empire on one side and the Habsburg Monarchy on the other, that ended the Austro–Turkish War (1737–39). This treaty ended the hostilities of the five-year Austro-Russian–Turkish War (1735–39), in which the Habsburgs