But at the critical moment Protestantism arose in Germany, marking a cleavage between the knightly leaders and the emperor. To knights like Ulrich von Hutten and Franz von Sickingen the final break in 1520 between Martin Luther and the pope seemed to assure a separation of Germany from Italy and the erection of a peculiar form of German Christianity about which a truly national state could be builded. As a class the knights applauded Luther and rejoiced at the rapid spread of his teachings throughout Germany. On the other hand, Charles V remained a Roman Catholic. Not only was he loyally attached to the religion of his fathers through personal training and belief, but he felt that the maintenance of what political authority he possessed was dependent largely on the maintenance of the universal authority of the ancient Church, and practically he needed papal assistance for his many foreign projects. The same reasons that led many German princes to accept the Lutheran doctrines as a means of lessening imperial control caused Charles V to reject them. At the same Diet at Worms (1521), at which the Council of Regency had been created, Charles V prevailed upon the Germans present to condemn and outlaw Luther; and this action alienated the knights from the emperor. [Sidenote: The Knights' War, 1522-1523] Franz von Sickingen, a Rhenish knight and the ablest of his class, speedily took advantage of the emperor's absence from Germany in 1522 to precipitate a Knights' War. In supreme command of a motley army of fellow-knights, Franz made an energetic attack upon the rich landed estates of the Catholic prince-bishop of Trier. At this point, the German princes, lay as well as ecclesiastical, forgetting their religious predilections and mindful only of their common hatred of the knights, rushed to the defense of the bishop of Trier and drove off Sickingen, who, in April, 1523, died fighting before his own castle of Ebernburg. Ulrich von Hutten fled to Switzerland and perished miserably shortly afterwards. The knights' cause collapsed, and princes and burghers remained triumphant. [Footnote: The Knights' War was soon followed by the Peasants' Revolt, a social rather than a political movement. For an account of the Peasants' Revolt see pp. 133 ff.] It was the end of serious efforts in the sixteenth century to create a national German state. [Sidenote: Failure of German Nationalism in the Sixteenth Century]