Duchy of Prussia

The Duchy of Prussia was created in 1525 when Albert of Hohenzollern, the last Grand Master of the Teutonic Order, secularised the Order's Prussian lands and converted them into a hereditary duchy. It was the first state in Europe to adopt Lutheranism officially, and Albert turned Königsberg into a centre of Protestant learning and printing. The duchy remained a fief of the Polish crown, and its relationship with Poland shaped its politics for more than a century. In 1618 it passed to the Hohenzollern electors of Brandenburg through a personal union, although the two territories remained legally separate. The Great Elector, Frederick William, won full sovereignty over Ducal Prussia in the Treaty of Wehlau in 1657, and in 1701 his son Frederick III crowned himself king in Königsberg, elevating the duchy to the Kingdom of Prussia. The duchy's capital, Königsberg, now Kaliningrad, remained the coronation city and a symbol of Prussian identity.