The expedition was considered all the more necessary because the Pope had taken sides against the Emperor, and his legate had declared before the Reichstag that the Emperor derived his authority from the Pope. This aroused the indignation of the German knights, who haughtily declared that the Emperor occupied a free throne given to him by the free choice of the German princes; that the Church was dependent upon the Empire; and that the latter would not permit any usurpation of its authority. An armed force more numerous and better equipped than any previous one crossed the Alps.[12] The Milanese this time appeared to be conciliatory, for, at the Emperor’s summons, a delegation went to him and sought to justify their conduct. Their explanations, however, did not satisfy either the Emperor or the knights, still less the other Italian cities which had suffered. Milan was declared under the ban of the Empire, promptly besieged, and forced to surrender after making a gallant defence. It was compelled to take the oath of loyalty, give up its plunder, and promise to let its neighbors rest in peace. The Milanese were also ordered to build an imperial castle and send three hundred hostages to the Emperor’s camp. The nobles and dignitaries, barefooted and with halters about their necks, begged for clemency. Frederick decided that it was not enough merely to punish crimes already committed. Wisdom dictated precaution against their commission in future. He therefore summoned four of the most experienced law authorities and required them to investigate and settle what rights belonged to the Empire and what to the cities. He was willing to concede all the rights of the latter, but he demanded that the cities should take a solemn oath to respect the rights of the Empire. Everything now appeared settled and most of the German princes returned home with their followers; but Frederick was anxious for the future, and remained in Italy to watch the progress of events. His fears were justified, for the wildest confusion soon prevailed. Milan, encouraged by the Emperor’s complications with the Pope, secured the help of Crema[13] and other cities, and the struggle began anew. Crema was besieged by Frederick, but made a stout defence. The dreadful struggle lasted seven months before Crema was forced to surrender. Abandoned by its citizens, it was sacked and then destroyed.