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. Sickingen's rising.