The unexpected turn which the war had taken in Saxony was not Charles' only trouble. Paul III had been alarmed by the Emperor's progress, which had been more rapid and complete than he expected, and at the end of six months, for which he had promised his contingent, he withdrew it. The material loss was slight, but the whole aspect of the war was altered. Charles could scarcely now profess to be fighting for submission to Pope and council, for the council in March transferred itself, after violent altercations with the Spanish bishops and imperial envoys, to Bologna. Rome rejoiced at the successes of John Frederick. In the late French war the Turks had figured as the Pope's friends and had spared his shores; it now seemed possible that the Lutherans might be the Pope's allies. It was certain that, if time were given, the Pope's defection would stimulate the active hostility of France. Charles must have done with the rebellion, and that quickly.
Tortured by gout and fearing that his forces would prove inferior to the Saxons, Charles moved painfully from Nordlingen to Regensburg and thence to Eger, where he was joined by Ferdinand, Maurice, and the electoral prince of Brandenburg. Spending Easter at Eger, he crossed the Saxon frontier on April 13, 1547, with eighteen thousand foot and eight thousand horse. Ten days of incessant marching brought him within touch of the Elector, who was guarding the bridge of Meissen. John Frederick had foolishly frittered away his forces in Saxon and Bohemian garrisons. He now burned the bridge and retired down the Elbe to Muehlberg, hoping to concentrate his scattered forces under the walls of Wittenberg, while his bridge of boats would keep open communications with the left bank.
Charles was too quick for the ponderous Elector. He marched at midnight on April 23-24, and at 9 a.m. reached the Elbe, nearly opposite Muehlberg. As the mist cleared, Alba's light horse descried the bridge of boats swinging from the farther bank, and a dozen Spaniards, covered by an arquebuse fire, swam the river with swords between their teeth, routed the guard, and brought the boats across. Meanwhile Alba and Maurice found a ford by which the light horse crossed with arquebusiers en croupe. Charles and Ferdinand followed, with the water up to the girths, the Emperor pale as death and thin as a skeleton. The Elector, after attending his Sunday sermon, was enjoying his breakfast; he made no attempt to defend his strong position on the higher bank, but withdrew his guns and infantry, covering the retreat in person with his cavalry. The bulk of the imperial forces had crossed by the bridge of boats, and the day was passed in a running rear-guard action. It was a long-drawn sunset, and not till between six and seven did Alba, as ever making sure, deliver his decisive attack. The Saxon horse had turned fiercely on the pursuing light cavalry some nine miles from Muehlberg, and then the imperialists, striking home, converted the retreat into a headlong flight. More than a third of the Saxon forces were left upon the field; the whole of their artillery and baggage train was taken. John Frederick regained his timid generalship by his personal bravery. Left almost single-handed in the wood through which his troops retired, he slashed at the Neapolitan light-horsemen and Hungarian hussars who surrounded him, but at length surrendered to Ippolito da Porto of Vicenza, who led him, his forehead streaming with blood, to Charles.
Of the interview between the Emperor and his enemy there are several versions, but none inconsistent. "Most powerful and gracious Emperor," said the Elector, vainly endeavoring to dismount, "I am your prisoner." "You recognize me as Emperor now?" rejoined Charles. "I am to-day a poor prisoner; may it please your majesty to treat me as a born prince." "I will treat you as you deserve," said Charles. Then broke in Ferdinand, "You have tried to drive me and my children from our lands."
The evidence as to the angry scene seems conclusive. Charles had been twenty-one hours in the saddle; he had been exasperated by the insolence of the Princess, who had addressed him as "Charles of Ghent, self-styled Emperor." Yet his harsh reception of a wounded prisoner contrasts unpleasantly with the generosity which his biographers have ascribed to him.
Muehlberg was little more than a skirmish, and yet it was decisive. In a far more murderous battle the imperialists were beaten. The forces of the maritime towns had compelled Eric of Brunswick to raise the siege of Bremen, and on his retreat had defeated him near Drakenberg with a heavy loss. But victories belated or premature do not turn the scale against an opportune success. The sole result of the battle was to delay the Landgrave's surrender a little longer. Philip had sworn to die like a mad-dog before he would surrender his fortresses, but he yielded ultimately without a blow. He found discontent rife among his nobles; he was threatened alike from the Netherlands and by the Count of Buren; for months he wavered between capitulation and resistance. Arras assured the nuncio that he was a scoundrel and a coward; that he had implored Maurice to intercede, first for all Lutheran Germany, then for John Frederick and himself, and finally for himself alone. "See what men these are," added the Bishop later. "Philip has even offered to march against the Duke of Saxony; he is a sorry fellow and of evil nature: he is such a scoundrel that his majesty cannot trust him in any promise that he may make, for he has never kept one yet."
The imperial minister's judgment upon the Landgrave was too severe. He long struggled for honor against fear, and, but for his son-in-law, Maurice's influence might have made a better fight. Maurice had from the first striven to detach Philip from John Frederick, while in turn he was expected by the Landgrave to strike in for a free Germany and a free gospel against the Hungarian hussars and the black Spanish devils. When the two Lutheran leaders parted in November, 1546, on no good terms, Philip warned his son-in-law that the Elector was on the march against him, but begged to intercede with Charles for a general peace. Maurice would have no peace with his Ernestine cousins, but offered to use all his influence on behalf of Philip, who must hasten to decide, for Buren was "on his legs" and the Emperor was an obstinate man. From this moment the Landgrave's irresolution was piteous; the negotiations crippled all enterprise, and yet he could not persuade himself to abandon his ally, although the natural expiry of the League of Smalkald on February 27, 1547, gave him a tolerable pretext. Maurice waxed impatient at the recurring hesitation, at the perpetual amendment of all suggested terms: Philip could not bargain with Charles as though he were a tradesman; he need have no fear for religion, but he must make it clear to the Emperor and Ferdinand that he was against John Frederick. Then came the defeat of Muehlberg, which at least relieved Philip from obligations to his late ally. It was now the surrender of his fortresses and his artillery that he could not stomach, and the victory of Drakenberg raised his once martial ardor to a final flicker.
The flicker died away, and at length Philip yielded to the pressure of Maurice and Joachim of Brandenburg. Charles insisted on unconditional surrender, but promised the mediators that punishment should not extend to personal injury or perpetual imprisonment—this only, however, on their pledge that Philip should not be informed of these limitations. It was agreed that he should dismantle his fortresses with one exception, surrender his artillery, and pay an indemnity, but that his territory should remain intact and its religion undisturbed.
With Philip's surrender the war seemed virtually at an end. Magdeburg, indeed, still held out, for fear of falling again under its Catholic Hohenzollern Archbishop. There was no reason to believe that the city would prove more courageous than its fellows. Charles did not dare spend his four thousand Spaniards in the assault, but in this case extravagance would have proved to be economy. When he knew his subject, his opinion was usually well founded; he had little knowledge, however, of North Germany, and confused Magdeburg with Ulm or Augsburg. It were better for Charles had his Spaniards been decimated on its parapet than that they should lord it in security over the churches and taverns of Southern Germany.
Apart from his two last mistakes, in the campaign against the league, Charles, whether as a soldier or statesman, is seen at his best. When once the drums beat to arms there was an end to irresolution. He had that reserve of energy upon which an indolent, lethargic nature can sometimes at a crisis draw. The Netherlands seemed threatened from east to west; yet in perfect calm he ordered his agitated sister Mary to watch her frontiers, but to send every man and gun that could be spared under Buren to the front. Taking advantage of his enemies' delays, he made with greatly inferior forces the forward move on Ingolstadt, and was there seen under heavy fire "steady as a rock and smiling." Racked by gout he now sought sleep in his litter behind a bastion, now warmed his aching limbs in a little movable wooden room heated by a stove. In the cold, wet November, when generals and ministers fell sick, and soldiers of every nationality deserted, he resolutely rejected expert advice to withdraw into winter quarters. He would not give his enemies, he said, the least chance of outstaying him. All success, wrote the Marquis of Marignano, was due to the Emperor's resolution to keep the field. Charles vexed the fiery Buren by shrinking from a general engagement, because he knew that his combinations would break up the league without the risk of a battle. But when once danger really pressed, ill as he was, he marched across Germany, and followed fast upon the Elector's heels until he tripped and took him.