Evidently Cardinal Borromeo was stimulating his suffragans to increased zeal and activity and when, in 1566, he came to reside in Milan, his ardor for the extermination of heresy grew apace, whether through his own convictions or through the impetuous urgency of the new Inquisitor-Pope, St. Pius V, whose aim was to subject the whole Christian world to the Holy Office.[250] There is a curious memorandum drawn up by Borromeo, detailing the matters to be enquired into in episcopal visitations, which shows that the persecution of heresy, the efficiency of the Inquisition, the avoidance of communication with heretics and the observances of the faith were regarded by him as the points of first importance.[251] In 1568 he was suddenly summoned to Mantua as the most fitting person to put the Inquisition there into working order. The duke, Guillelmo Gonzaga, was liberally inclined and had long given trouble to the Holy Office. Pius V, soon after his accession, in 1566, had been moved to pious wrath by his refusal to send to Rome two heretics for trial. A threat to bring him to terms by open war failed and Pius would have proceeded to extremities, had he not been dissuaded by the other Italian princes.[252] He contented himself with sending orders to the inquisitor there, Fra Ambrogio Aldegato, to clear the city of heretics, who were numerous, but the frate was old; he shrank from the struggle and, pleading age and infirmity, he asked to be relieved. Pius gave him the bishopric of Casale and extended over Mantua the jurisdiction of Fra Camillo Campeggio, styled Inquisitor-general of Ferrara, who had doubtless been selected as a man of vigor for that post, in view of the encouragement to the reform given not long before by Renée de France, the Duchess of Ferrara. The new inquisitor was not favorably regarded by Gonzaga, who interfered with the public penances and abjurations imposed by him, who was slack in obeying his commands to make arrests and who even allowed suspected heretics to escape. Campeggio was more earnest than respectful in his remonstrances and mutual ill-will increased until, on Christmas night of 1567, some sons of Belial slew two Dominicans who had doubtless been overzealous in aiding the inquisitor. No active efforts were made to detect the assassins; some higher authority was evidently needed and Pius V, by a brief of February 12, 1568, ordered Cardinal Borromeo to go there with all speed, to bring the duke to obedience and to sit with the inquisitor in the trial of cases. Borromeo lost no time in obeying the mandate and, on his arrival he gave the duke to understand that the pope’s determination was unalterable; he would rather see all Dominicans cut to pieces, and all Dominican convents burnt, than that heresy should go unpunished in Mantua. It required resolute action for there were heretics high-placed in both Church and State; a company of sbirri had to be borrowed from Bologna, but Borromeo succeeded in breaking down all