Duchy of Prussia

The Duchy of Prussia (Herzogtum Preußen, Księstwo Pruskie, Prūsijos kunigaikštystė) or Ducal Prussia (Herzogliches Preußen; Prusy Książęce) was a duchy in the region of Prussia established as a result of secularization of the Monastic Prussia, the territory that remained under the control of the State of the Teutonic Order until the Protestant Reformation in 1525. The duchy became the first Protestant state when Albert, Duke of Prussia formally adopted Lutheranism in 1525. It was inhabited by a German, Polish (mainly in Masuria), and Lithuanian-speaking (mainly in Lithuania Minor) population. In 1525, during the Protestant Reformation, in accordance to the Treaty of Kraków, the Grand Master of the Teutonic Knights, Albert, secularized the order's prevailing Prussian territory (the Monastic Prussia), becoming Albert, Duke of Prussia. As the region had been a part of the Kingdom of Poland since the Second Peace of Thorn (1466), King of Poland Sigismund I the Old, as its suzerain, granted the territory as a hereditary fief of Poland to Duke Albert per the Treaty of Kraków, a decision that was sealed by the Prussian Homage in Kraków in April 1525. The new duke established Lutheranism as the first Protestant state church. The capital remained in Königsberg (modern Kaliningrad). The duchy was inherited by the Hohenzollern prince-electors of Brandenburg in 1618. This personal union is referred to as Brandenburg-Prussia. Frederick William, the "Great Elector" of Brandenburg, achieved full sovereignty over the duchy under the 1657 Treaty of Wehlau, confirmed in the 1660 Treaty of Oliva. In the following years, attempts were made to return to Polish suzerainty, especially by the capital city of Königsberg, whose burghers rejected the treaties and viewed the region as part of Poland. The Duchy of Prussia was elevated to a kingdom in 1701. As Protestantism spread among the laity of the Teutonic Monastic State of Prussia, dissent began to develop against the Roman Catholic rule of the Teutonic Knights, whose Grand Master, Albert, Duke of Prussia, a member of a cadet branch of the House of Hohenzollern, lacked the military resources to assert the order's authority.