Gregory soon found that he had gone too far—that the humiliation at Canosa could never be forgotten and could never even sleep until it was revenged. Compassion as well as interest moved many princes and prelates to gather round the fallen king, now that he was released from the ban of excommunication. Hildebrand was generally hated because of his political tyranny, and dreaded because of his ecclesiastical censures. The revolted princes of Germany were secretly encouraged by the pope to dispute the possession of the throne with Henry, which increased his perplexity, and prevented him from turning his arms against Rome. He prayed that Henry might never prosper in war, and, in the name and with the blessing of the apostles, he bestowed the kingdom of Germany on the rebel, Rudolph, duke of Swabia. The pope even ventured to prophesy that within a year Henry would either be dead or deposed; and, as if he knew the end from the beginning, he sent a crown to the future king, with an inscription, signifying that it was the gift of Christ to St. Peter, and of St. Peter to Rudolph. But he was soon proved to be a lying prophet as well as a lying priest, and the remorseless fomenter of civil war.
The king's strength gradually increased in spite of all the wicked and cruel plottings of Gregory. After years of the most terrible civil war and fearful bloodshed, the armies of Henry and of his rival, Rudolph, met once more on the bank of the Ulster, in October 1080. The engagement was long and obstinate, but the fall of Rudolph gave Henry the victory. He received his death-wound, it is said, from the lance of Godfrey, afterward the first king of Jerusalem; a saber-wound from another cut off his right hand. It is reported that the dying prince, looking on his dissevered hand, sorrowfully acknowledged, "With this hand I ratified my oath of fealty to my sovereign, Henry: the punishment is just; I have now lost life and kingdom." The king's adversaries being now discouraged and paralyzed, he determined on turning his forces against his most formidable and irreconcilable enemy. He crossed the Alps, entered Italy, and encamped under the walls of Rome.
The city having been well provisioned, the walls strengthened, and the loyalty of the Romans secured by the wealth of Matilda, Henry was more or less engaged for three years in blockading and besieging Rome; but in the summer of 1083 he gained possession of the guilty city. Gregory took refuge in the strong castle of St. Angelo, and a few of his partisans in their fortified houses. Henry was willing to come to terms with Hildebrand, and to accept the imperial crown from his hands. But the pope would hear of nothing but unconditional submission. "Let the king resign his dignity, and submit to penance," were the only terms of Gregory. The clergy—bishops, abbots, and monks, and the laity, entreated him to have mercy on the afflicted city, and come to terms with the king.
But all attempts at negotiation were fruitless; the inflexible pope despised alike supplications and threatenings. The absolute submission of Henry, and satisfaction to the church, were the lofty demands of the imprisoned pope. But Henry was no longer the deserted, the broken-spirited, suppliant at his feet, as at Canosa.