Peace of Passau
In 1548, the victorious Charles forced the Schmalkaldic League to agree to the terms set forth in the Augsburg Interim. However, by the 1550s, Protestantism had established itself too firmly within Central Europe to be ended by brute force. A small Protestant victory in 1552 forced Charles to flee across the Alps to avoid capture; the heir Ferdinand (King of the Romans) signed the Peace of Passau, which granted some freedoms to Protestants and ended all of Charles' hopes of religious unity within his empire. Three years later, the Peace of Augsburg granted Lutheranism official status within the Holy Roman Empire and let princes choose the official religion within the domains that they controlled, according to the principle of "Cuius regio, eius religio".