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
History of the Lands of the Bohemian Crown (1526–1648) German territory. Czechs fought on all sides: most of the rebellious Czech generals joined Protestant armies; Albrecht of Wallenstein was the most prominent Czech defector to the imperial cause. Bohemia served as a battlefield throughout the war. Prince Bethlen Gabor's Hungarian forces, reinforced by Turkish mercenaries, fought against the emperor and periodically devastated Slovakia and Moravia. Protestant German armies and, later, Danish and Swedish armies, laid waste the Czech provinces. Cities, villages, and castle fortresses were destroyed. Lusatia was incorporated into Saxony in 1635. In 1648 the Treaty of Westphalia confirmed the incorporation of the Bohemian Kingdom into the Habsburg