Charles V. summoned a Diet to meet at Augsburg (1547), where he hoped that a permanent understanding might be secured. A document known as the /Augsburg Interim/, prepared by Catholic theologians in conjunction with the Lutheran, John Agricola, was accepted provisionally by both parties. The doctrines were expressed in a very mild form, though not, however, altogether unacceptable to Catholics. Protestants were permitted to receive communion under both kinds; their married clergy were allowed to retain their wives; and it was understood tacitly that they might keep possession of the ecclesiastical property they had seized. The /Augsburg Interim/, as might have been anticipated, was displeasing to both parties. Maurice of Saxony, unwilling to give it unconditional approval, consulted Melanchthon and others of his school as to how far he might accept its terms. In their reply they distinguished between matters that were essential and those that were only of secondary importance. The latter might be accepted unreservedly in obedience to the orders of the Emperor. In regard to doctrines, they were willing to compromise on the question of justification and good-works, to accept the sacraments, including confirmation and Extreme Unction, the Mass with the addition of some German hymns, and in a certain sense the jurisdiction of the bishops. Such concessions were a distinct departure from Luther's teaching and would have been impossible had he been alive. The relations between the Pope and the Emperor took a more friendly turn when the General Council was transferred from Bologna to Trent (1551). The Protestant princes, invited to send representatives, declined at first, but in a short time several of them agreed to accept the invitation. Safe conducts were issued for their representatives by the Council in 1551 and again in 1552. Even the Wittenberg theologians were not unfavourably disposed, and Melanchthon was actually on his way to Trent. But suddenly Maurice of Saxony, who had assembled a large army under pretext of reducing Magdeburg, and had strengthened himself by an alliance with several princes as well as by a secret treaty with Henry II. of France, deserted the Emperor and placed himself at the head of the Protestant forces. When all his plans were completed he advanced suddenly through Thuringia, took Augsburg, and was within an inch of capturing the Emperor who then lay ill at Innsbruck (1552). At the same time the French forces occupied Lorraine. Charles, finding himself unable to carry on the struggle, opened negotiations for peace, and in 1552 the Treaty of Passau was concluded. Philip of Hesse was to be set at liberty; a Diet was to be called within six months to settle the religious differences; in the meantime neither the Emperor nor the princes should interfere with freedom of conscience; and all disputes that might arise were to be referred to a commission consisting of an equal number of Protestant and Catholic members.