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 Grimnitz Sweden refused to hand over the duchy. An agreement was reached to partition the duchy into a Swedish and a Brandenburgian part in the Peace of Westphalia (1648), which was put into effect in the Treaty of Stettin (1653). Treaty of Grimnitz The Treaty of Grimnitz (26 August 1529) was the final settlement of a long-standing dispute between the House of Pomerania and the House of Hohenzollern regarding the legal status and succession in the Duchy of Pomerania. It renewed and amended the Treaty of Pyritz of 1493. With some formal caveats, the House of Pomerania received the Duchy of