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
War of the Spanish Succession was reliant on the so-called "Maritime Powers" (England and the Dutch Republic) and also a higher priority for them. By formalising religious divisions within the Empire, the [[Peace of Westphalia|1648 Peace of Westphalia]] weakened its integrity and by 1700, the larger German states were pursuing their own policies. [[Electorate of Bavaria|Bavaria]] allied itself with France while as King of Poland, [[Augustus II the Strong|Augustus of Saxony]] was fully occupied by the [[Great Northern War]]. To gain [[Frederick I of Prussia|Frederick of Prussia]]'s support, Leopold recognised him as King, with Prussia made an equal member of the Grand Alliance. [[George I