the college of cardinals received its first definite constitution as the electors of the Pope, Nicholas II held a council at the Norman hill-fortress of Melfi, attended by the higher clergy of the south and also by the two chief Norman princes, Richard of Aversa and Robert Guiscard. In return for the Pope's investiture of their lands, these princes took an oath of allegiance and fealty to the Holy See and agreed to pay an annual rent to the Pope for their domains; in Robert's oath, which has been preserved, he styles himself "by the grace of God and St. Peter duke of Apulia and Calabria and, with their help, hereafter of Sicily." As duke and vassal of the Pope, the cattle-thief of the Calabrian mountains had henceforth a recognized position in feudal society.
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
