the time, large portions of its territory in the north lay in what today is Lower Saxony. Following the deposition of the Saxon duke Henry the Lion in 1180 and the subsequent belittlement of the duchy, Westphalia was elevated to a duchy in its own right by Emperor Barbarossa. The Duchy of Westphalia comprised only a small area south of the Lippe River. Modern Westphalia was a part of the Lower Rhenish–Westphalian Circle of the Holy Roman Empire, which comprised territories of Lower Lorraine, Frisia and parts of the former Duchy of Saxony. Early modern era As a result of the Protestant Reformation, there was no dominant religion in Westphalia. Roman Catholicism and Lutheranism were on a relatively equal footing. Lutheranism was strong in the eastern and northern parts with numerous free churches. Münster and especially Paderborn were considered 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". Prussia 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 French client Kingdom of Westphalia until 1813, when the kingdom was dissolved by the Russians. While this state shared its name with the historical region, it only contained a relatively small part of Westphalia, rather consisting of mostly Hessian and Eastphalian regions. Following to the Congress of Vienna, Prussia received a large amount of territories in the Westphalian region and created the Province of Westphalia in 1815. After in 1816, the former Duchy of Westphalia and the counties of Wittgenstein and in 1851 the condominium of Lippstadt had joined the province, Westphalia had received its modern territorial shape. In 1816, the governmental districts of Arnsberg, Minden and Münster were created. Modern Westphalia After World War II in 1946, the present state of North Rhine-Westphalia was created by the British military government from the former Prussian Province of Westphalia and the northern half of the former Prussian Rhine Province. The old governmental districts of 1816 stayed in place. When in 1947