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
League of the Rhine of the 1648 treaty of Westphalia, the treaty which had made the League possible by authorising the German princes, immediate vassals of the Emperor, to conclude alliances between themselves or with foreign states. On August 14, 1658, the League of the Rhine was formed by: The League fielded a force of 6000 to fight on the side of France and the Empire against the Ottomans, seeing action in the 1664 Battle of Saint Gotthard. The League was promulgated to last for three years, and this was later twice extended. It officially ended in August 1667, its end should in fact