The elder son of Joachim I, Joachim II was given the Old (Altmark) and Middle Marks of Brandenburg on his father's death in 1535. Although he remained a Catholic, he sympathized with the Reformation and tolerated Protestantism in his lands from 1539 on. His religious liberalism was rewarded when the Brandenburg estates twice paid his considerable debts. In the disputes between the Emperor and Germany's Protestant princes, Joachim tried to reconcile the two parties. He sided with Charles V during the wars against the Schmalkaldic League of Protestant princes. After the Protestant defeat at the Battle of Mühlberg (1547), he persuaded Philip the Magnanimous, landgrave of Hesse, to surrender and was instrumental in securing a pardon for John Frederick I the Magnanimous of Saxony, who had been condemned to death. Joachim supported the Augsburg Interim (1548) and played a major role at the negotiations leading to the Peace of Augsburg (1555), which reestablished peace in Germany between the warring religious factions. Finally, in 1569, two years before his death, he received the duchy of Prussia as a fief from King Sigismund II Augustus of Poland.