The Peace of Augsburg was a treaty signe between Ferdinand, who replaced his brother Charles V as Holy Roman Emperor, and the forces of the Schmalkaldic League, an alliance of Lutheran princes, on September 25, 1555, at the city of Augsburg in Bavaria, Germany. It officially ended the religious struggle between the two groups and made the legal division of Christendom permanent within the Holy Roman Empire. In respect of the famous quote "Cuius regio, eius religio", derived from the document allowed German princes to select either Lutheranism or Catholicism within the domains they controlled, ultimately reaffirming the independence they had over their states. Families were given a period in which they were free to migrate to different regions of their desired religion.