The progress of Gustavus Adolphus along the shores of the river Main to the towns of Frankfort and Mayence was a march of triumph. In capturing Mayence, the Swedes fought the Spanish allies of the emperor. The towns surrendered to violence or by their own consent. Gustavus Adolphus made their inhabitants pledge their fidelity to him and strengthened his power with the rich resources of the Frankish country. Then he turned against Maximilian of Bavaria. Tilly, who was to defend Bavaria, was again encountered and defeated at Lech. He was carried from the battle mortally wounded and died soon afterward. Gustavus Adolphus made his triumphal entry into Munich, with Frederic of the Palatinate at his side. The danger to the crown lands of the emperor was imminent. Wallenstein was the most famous of German generals. Reticent and secretive, he appeared to be unable to feel mercy. He was devoted to the secret doctrines of astrology, which in him had taken the place of religion. He cared naught for the cause of religious liberty or the fall of the German empire, looking only for occasions to satisfy his own ambition and the means of obtaining power and wealth. He had served the emperor, who had raised him to the dignity of a duke of Mecklenburg, but had been dismissed and deprived of his dignities at the time of the arrival of Gustavus Adolphus on German soil. His downfall was caused by complaints of his insolence and recklessness, made by Maximilian of Bavaria and other German princes. Wallenstein retired to Prague, at the castle of which town he surrounded himself with princely luxury and comfort, scheming for revenge. His plan was to join the enemies of the emperor. He approached Gustavus Adolphus for such purpose, before the battle of Breitenfeld, and was delighted to hear of the defeat of Tilly. Gustavus Adolphus seemed at first inclined to take up relations with Wallenstein, but at the point where an agreement was to be made he suddenly changed his attitude. The king probably hesitated to accept the services of a man who had no other aim than to satisfy his own ambition. The emperor was placed in a bad predicament, at the second defeat of Tilly, for want of an army to defend his lands and a commander to lead it. There was only one way out of the difficulty, and that was to pacify the mortally offended Wallenstein, and to persuade him to re-enter the service of the emperor. The emperor resigned himself to accept this humiliating condition, and Wallenstein agreed to resume command, but only at a high price. The name of Wallenstein was enough to bring thousands of warriors under the imperial banners, and Wallenstein was soon at the head of an army of sufficient proportions. His doctrine was that “the war should support itself,” according to which his soldiers were allowed to sack and plunder at will the countries through which they were passing. He cared naught for the recklessness of his subordinates, if they only showed blind obedience to him.