He played a leading role in establishing the Protestant religion in Germany and in asserting German princely independence against Emperor Charles V. After becoming converted to Luther’s doctrines (1524), Philip turned Hesse into a Protestant state. He was active at the Diet of Speyer (1529), a subscriber to the Augsburg Confession (1530), and became a founder and leader of the Schmalkaldic League, an alliance of Protestant princes and cities (1531). He forfeited the loyalty of some of his followers by marrying bigamously (1540) and after his defeat in the Schmalkaldic War he was imprisoned by Charles V. He lived to see Lutherans achieve equality with Catholics under the Peace of Augsburg (1555).