 1466 and 1525 arrangements by kings of Poland were not verified by the Holy Roman Empire, as well as the previous gains of the Teutonic Knights, were not verified.The Teutonic Order lost eastern Prussia when Grand Master Albert of Brandenburg-Ansbach converted to Lutheranism and secularized the Prussian branch of the Teutonic Order in 1525.Albert established himself as the first duke of the Duchy of Prussia and a vassal of the Polish crown by the Prussian Homage.