Guiscard, however, was not the man to rest content with the position he had won, or to interpret his obligation of vassalage as an obligation of obedience. He was soon in the field again, pushing up the west coast to Amalfi and up the east into the Abruzzi, taking no great pains as he went to distinguish the lands of St. Peter from the lands of others. The Pope began to ask himself what he had secured by the alliance, and a definite break was soon followed by the excommunication of the Norman leader. By this time the papal see was occupied by Gregory VII, who as Hildebrand had long been the power behind the throne under his predecessors, the greatest, the most intense, and the most uncompromising of the Popes of the eleventh century; yet even he failed to bend the Norman to his will. Fearing a combination with his bitterest enemy, the Emperor Henry IV, he finally made peace with Guiscard, and in the renewal of fealty and investiture which followed, the recent conquests of the Normans were expressly excepted. No great time elapsed before the Pope was forced to make a desperate appeal for Norman aid. After repeated attempts Henry IV got control of Rome, shut up Gregory in the Castle of Sant’ Angelo, and installed another Pope in his place, who crowned Henry emperor in St. Peter’s. Then, in May, 1084, Guiscard’s army came. The emperor made what might be called ‘a strategic retreat’ to the north, the siege of Sant’ Angelo was raised, and Rome was given over to butchery and pillage by the Normans and their Saracen troops. Fire followed the sword, till the greater part of the city had been burned. Ancient remains and Christian churches such as San Clemente were ruined by the flames, and quarters like the Cælian Hill have never recovered from the destruction. The monuments of ancient Rome suffered more from the Normans than from the Vandals. Unable to maintain himself in Rome without a protector, Gregory accompanied his Norman allies southward as far as Salerno, now a Norman city, where he died the following year, protesting to the last that he died in exile because he had “loved justice and hated iniquity.” The year 1085 also saw the end of Robert Guiscard. Sought as an ally alike by the emperors of the East and of the West, he had begun three years earlier a series of campaigns against the Greek empire, seizing the ports of Avlona and Durazzo which were then as now the keys to the Adriatic, and battling with the Venetians by sea and the Greeks by land until his troops penetrated as far as Thessaly. He finally succumbed to illness on the island of Cephalonia at the age of seventy, and was buried in his Apulian monastery of Venosa, where Norman monks sang the chants of Saint-Évroul over a tomb which commemorated him as “the terror of the world”:-- Hic terror mundi Guiscardus; hic expulit Urbe Quem Ligures regem, Roma, Lemannus habent. Parthus, Arabs, Macedumque phalanx non texit Alexin. At fuga; sed Venetum nec fuga nec pelagus.[64]