Thus was destroyed in Florence the power of the heretics and of the Ghibellines. Ruggieri, for his steadfast courage, was rewarded, before the close of 1245, with the bishopric of Castro, and was succeeded as inquisitor by San Piero himself, whose indefatigable zeal allowed the heretics no rest. Many of them, recognizing the futility of further resistance, abandoned their errors; others fled, and when Piero left Florence he could boast that heresy was conquered and the Inquisition established on an impregnable basis; though Rainerio’s estimate of the Florentine Cathari, some years later, shows that it still had an ample harvest to reward its labors.[235] While Ruggieri, in the summer of 1245, was precipitating the conflict in Florence, Innocent IV., in the Council of Lyons, was passing sentence of dethronement on Frederic II. and trying to find some aspirant hardy enough to accept the imperial crown. Frederic laughed the sentence to scorn and easily disposed of his would-be competitors, but he was obliged to struggle hard to maintain his Italian possessions, and his death, December 13, 1250, relieved the papacy from the most formidable antagonist which its ambitious designs had ever encountered. Skilled equally in the arts of war and peace, untiring in activity, dismayed by no reverses, intellectually far in advance of his age, and encumbered with few scruples, Frederic’s brilliant abilities and indomitable courage had been the one obstacle in the papal path towards domination over Italy and the foundation on that basis of a universal theocratic monarchy. His son, Conrad IV., a youth of twenty-one, was scarce to be dreaded in comparison, though Innocent cautiously waited for a while in Lyons before venturing into Italy. After reaching Genoa, June 8, 1251, he addressed to Piero da Verona and Viviano da Bergamo a brief which shows that the intervening six months had not sufficed to dull the sense of rejoicing at the death of his great opponent, and that no more time was to be lost in taking full advantage of the opportunity. A dithyrambic burst of exultation is followed by the declaration that thanks to God for this inestimable mercy are to be rendered not so much in words as in deeds, and of these the most acceptable is the purification of the faith. Frederic’s favor towards heretics had long impeded the operations of the Inquisition throughout Italy, and now that he is removed it is to be put into action everywhere with all possible vigor. Inquisitors are to be sent into all parts of Lombardy; Piero and Viviano are ordered to proceed forthwith to Cremona, armed with all necessary powers; rulers who do not zealously assist them will be coerced with the spiritual sword, and, if this proves insufficient, Christendom will be aroused to destroy them in a crusade. This bull was followed by a rapid succession of others addressed to the Dominican provincials and to potentates, ordering strenuous co-operation, and the