And yet it was for precisely this end that Charles chiefly valued his authority. Immediately, acting independently of the pope, he made another effort to restore the confessional unity of Germany. The Diet of Augsburg [Sidenote: 1547-8] accepted under pressure from him a decree called the Interim because it was to be valid only until the final decisions of a general council. Though intended to apply only to Protestant states--the Catholics had, instead, a _formula reformationis_--the Interim [Sidenote: The Interim, June 30, 1548], drawn up by Romanist divines, was naturally Catholic in tenor. The episcopal constitution was restored, along with the canon of the mass, the doctrine of the seven sacraments, and the worship of saints. On some doctrinal points vagueness was studied. The only concessions made to the Reformation were the _pro tempore_ recognition of the marriage of the clergy and the giving of the cup to the laity. Various other details of practical reform were demanded. The Interim was intensely unpopular with both parties. The pope objected to it and German Catholics, especially in Bavaria, strongly opposed it. The South German Protestant states accepted it only under pressure. Maurice of Saxony adopted it in a modified form, known as the Leipzig Interim, in December 1548. The assistance rendered him by Melanchthon caused a fierce attack on the theologian by his fellow-Lutherans. In enforcing the Interim Maurice found his own profit, for when Magdeburg won the nickname of "our Lord God's pulpit" by refusing to accept it, Maurice was entrusted with the execution of the imperial ban, and captured the city on November 9, 1551. Germany now fell into a confused condition, every state for itself. The emperor found his own {130} difficulties in trying to make his son Philip successor to his Brother Ferdinand. His two former Protestant allies, Maurice and John von Kuestrin, made an alliance with France and with other North German princes and forced the emperor to conclude the Convention of Passau. [Sidenote: 1552] This guaranteed afresh the religious freedom of the Lutherans until the next Diet and forced the liberation of John Frederic and Philip of Hesse. Charles did not loyally accept the conditions of this agreement, but induced Albert, Margrave of Brandenburg-Culmbach, to attack the confederate princes in the rear. After Albert had laid waste a portion of North Germany he was defeated by Maurice at the battle of Sievershausen. [Sidenote: July 9, 1553] Mortally wounded, the brilliant but utterly unscrupulous victor died, at the age of thirty-two, soon after the battle. As the conflict had by this time resolved itself into a duel between him and Charles, the emperor was now at last able to put through, at the Diet of Augsburg, a settlement of the religious question. [Sidenote: Religious Peace of Augsburg, September 25, 1555] The principles of the Religious Peace were as follows: