His courage had its reward. Margrave Albrecht 'had separated from his allies and was pursuing a wild career of murder and sacrilege in Franconia, where he dreamt of carving a secular duchy out of the Bishops' spiritualities; in six weeks he extorted nearly a million crowns by way of ransom. Maurice failed in his attack on Frankfort, where he lost one of his ablest lieutenants by the death of George of Mecklenburg. The advance of Henry II had been checked by the valour of Strassburg; Charles had released John Frederick, and with a little help the Ernestine Wettin could raise a storm which would drive his cousin from Saxony; while Hans of Custrin would willingly join in the fray in return for a share of the Albertine lands. Conscious that the nation was not really behind him and that he would lose his all by defeat, Maurice reluctantly yielded to Charles' demand that the religious question should be left to a Diet. Margrave Albrecht roughly refused to accept the peace; and when Maurice marched to help Ferdinand against the Turks, many of his troops mutinied and took service with Albrecht. The Margrave's disgust was not due to zeal for the Protestant faith, but to the fact that Maurice had played both hands in the game and reduced his partner to a dummy. Fortune seemed to be turning and Charles thought of refusing to ratify the treaty, delayed the liberation of Philip of Hesse, and returned to his schemes for creating a friendly league and securing the Empire for his son. He appeared to have learnt and forgotten nothing, but his advisers were more amenable. Queen Maria opposed these plans, Ferdinand denounced them, and the fear lest his obstinacy should drive his brother into Maurice's arms induced Charles to submit and sign the Treaty of Passau.
Reluctantly the Emperor surrendered for the moment his dynastic projects and assumed the part of the champion of Germany against the French invader. Emerging from Villach and journeying by way of Augsburg, where he could not refrain from once more overthrowing the democratic government and expelling some of the more obnoxious preachers who had returned in Maurice's train, Charles appeared on the Rhine determined to wrest Metz, Toul, and Verdun from the French. Metz was the key of the situation, and it had been amply provisioned and skilfully fortified by the Duke of Guise. On the last day of October, 1552, the siege was formally opened, and Charles strengthened his forces by an unscrupulous alliance with Albrecht Alcibiades. The Margrave's brutalities had roused all Franconia against him and he had been forced to flee to the Court of Henry II; but Court life had no attractions for him, and the French King hesitated to entrust so doubtful an ally with important commands. So Albrecht escaped, captured the Duke of Aumale, and with this peace-offering came into Charles' camp. His terms were the imperial sanction of his spoliation of the Bishops of Würzburg and Bamberg. "Necessity knows no law," wrote Charles to his sister, as he struck his bargain with the worst law-breaker in
