 In the same year he mediated between the Teutonic Grand Master Albert of Brandenburg and King Sigismund I of Poland, for the possession of Prussia, which eventually became the secular Duchy of Prussia in 1525, with Albert as its Duke but under Polish sovereignty.From 1523 Frederick II was a strong supporter of the Reformation and founded in 1526 the first Protestant University in Legnica; however, because of the controversies between Luther and Caspar Schwenckfeld, it wasn't until 1530 that the University finally opened.Despite his own conversion to Protestantism, Frederick II allowed his subjects to choose their own religion.