When Charles was chosen German king he was obliged to make certain promises to the electors. Embodied in a _Wahlkapitulation_, as it was called, these were practically the conditions on which the new sovereign was allowed to take the crown, and the precedent was followed at subsequent elections. At the diet of Worms steps were taken to carry these promises into effect. By his _Wahlkapitulation_ Charles had promised to respect the freedom of Germany, for the princes looked upon him as a foreigner. He was neither to introduce foreign troops into the country, nor to allow a foreigner to command German soldiers; he must use the German language and every diet must meet on German soil. An administrative council, a new _Reichsregiment_, must be established, and other reforms were to be set on foot. The constitution and powers of this _Reichsregiment_ were the chief subject of difference between Charles and the princes at the diet. Eventually it was decided that this council should consist of twenty-two members with a president named by the emperor; but it was only to govern Germany during the absence of the sovereign, at other times its functions were merely advisory. The imperial chamber was restored on the lines laid down by Bertold of Mainz in 1495 (it survived until the dissolution of the Empire in 1806), and the estates undertook to aid the emperor by raising and paying an army. In April 1521 Charles invested his brother Ferdinand, afterwards the emperor Ferdinand I., with the Austrian archduchies, and soon afterwards he left Germany to renew his long struggle with Francis I. of France.
While the emperor was thus absent great disturbances took place in Germany. Among Luther's friends was one, Ulrich von Hutten, at once penetrated with the spirit of the Renaissance and emphatically a man of action. The class to which Hutten and his friend, Franz von Sickingen, a daring and ambitious Rhenish baron, belonged, was that of the small feudal tenants in chief, the _Ritterschaft_ or knights of the Empire. This class was subject only to the emperor, but its members lacked the territorial possessions which gave power to the princes; they were partly deprived of their employment owing to the suppression of private wars, and they had suffered through the substitution of Roman law for the ancient feudal laws and customs. They had no place in the constitution or in the government of Germany, and they had already paralysed the administration by refusing to pay the taxes. They were intensely jealous of the princes, and it occurred to Hutten and Sickingen that the Reformation might be used to improve the condition of the knights and to effect a total change in the constitution of the Empire. No general reform, they maintained, either in church or state, could be secured while the country was divided into a number of principalities, and their plan was to combine with all those who were discontented with the existing order to attack the princes and to place the emperor at the head of a united nation. Sickingen, who has been compared to Wallenstein, and who doubtless hoped to secure a great position for himself, had already collected a large army, which by its very presence had contributed somewhat to the election of Charles at Frankfort in 1519. He had also earned renown by carrying on feuds with the citizens of Worms and of Metz, and now, with a view to realizing his larger ambitions, he opened the campaign (August 1522) by attacking the elector of Trier, who, as a spiritual prince, would not, it was hoped, receive any help from the religious reformers. For a moment it seemed as if Hutten's dream would be realized, but it was soon evident that it was too late to make so great a change. Luther and other persons of influence stood aloof from the movement; on the other hand, several princes, including Philip, landgrave of Hesse, united their forces against the knights, and in May 1523 Sickingen was defeated and slain. A few weeks later Hutten died on an island in the lake of Zürich.