In the aftermath of the armistice ending the Polish-Teutonic War Albert, Grand Master of the Teutonic Knights and a member of the House of Hohenzollern, visited Martin Luther at Wittenberg and soon thereafter became sympathetic to Protestantism. On 10 April 1525, two days after signing of the Treaty of Kraków which officially ended the Polish–Teutonic War (1519–21), in the main square of the Polish capital Kraków, Albert resigned his position as Grand Master of the Teutonic Knights and received the title "Duke of Prussia" from King Zygmunt I the Old of Poland. In the deal, partially brokered by Luther, the Duchy of Prussia became the first Protestant state, anticipating the Peace of Augsburg of 1555. The investiture of a Protestant fief of Duchy of Prussia was better for Poland for strategic reasons than a Catholic fief of State of Teutonic Order in Prussia, formally subject to the Holy Roman Emperor and the Papacy.