He then received one-half the Sacred Host, and turning to the king, offered him the remaining half, bidding him to follow his example, if he held himself to be guiltless. Henry refused the ordeal, doubtless because he did not dare to risk the penalty, and was glad enough to escape from the presence of the pope, a humble penitent. This ended Henry's career of humiliation. It was followed by a period of triumph. On leaving the castle of Canossa he found the people of Lombardy so indignant at his cowardice, that their scorn induced him to break the oath he had just taken, gather an army, and assail the castle, in which he shut up the pope so closely that he could neither proceed to Augsburg nor return to Rome. This siege, however, was not of long continuance. Henry soon found himself recalled to Germany, where his enemies had elected Rudolf, Duke of Swabia, emperor in his stead. A war broke out, which continued for several years, at the end of which Gregory, encouraged by a temporary success of Rudolf's party, pronounced in his favor, invested him with the empire as a fief of the papacy, and once more excommunicated Henry. It proved a false move. Henry had now learned his own power, and ceased to fear the pope. He had strong support in the cities and among the clergy, whom Gregory's severity had offended, and immediately convoked a council, by which the pope was again deposed, and the Archbishop of Ravenna elected in his stead, under the title of Clement III. In this year, 1080, a battle took place in which Rudolf was mortally wounded, and the party opposed to Henry left without a leader, though the war continued. And now Henry, seeing that he could trust his cause in Germany to the hands of his lieutenants, determined to march upon his pontifical foe in Italy, and take revenge for his bitter humiliation at Canossa. He crossed the Alps, defeated the army which Matilda had raised in the pope's cause, and laid siege to Rome, a siege which continued without success for the long period of three years. At length the city was taken, Wilprecht von Groitsch, a Saxon knight, mounting the walls, and making his way with his followers into the city, aided by treachery from within. Gregory hastily shut himself up in the castle of St. Angelo, in which he was besieged by the Romans themselves, and from which he bade defiance to Henry with the same inflexible will as ever. Henry offered to be reconciled with him if he would crown him, but the vigorous old pontiff replied that, "He could only communicate with him when he had given satisfaction to God and the church." The emperor, thereupon, called the rival pope, Clement, to Rome, was crowned by him, and returned to Germany, leaving Clement in the papal chair and Gregory still shut up in St. Angelo.