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
Stralsund Treaty of Stettin (1630), the town became one of two major Swedish forts in the Duchy of Pomerania, alongside Stettin (now Szczecin, Poland). After the war, the Peace of Westphalia (1648) and the Treaty of Stettin (1653) made Stralsund part of Swedish Pomerania. Lost to Brandenburg in the Battle of Stralsund (1678), it reverted to Sweden in the Treaty of Saint-Germain-en-Laye (1679). In the Great Northern War in 1715 Charles XII led the defence of Stralsund for a year against the united European armies. Stralsund remained under Swedish control until the Battle of Stralsund (1807), when Napoleon Bonaparte's army occupied