Gregory’s pursuit of heresy did not stop with the city of Rome. Later that year, while collecting still outstanding debts from the War of the Keys from communities in Campagna, he took action against the lords of the commune of Miranda, who were known by “public infamy” to be “supporters of heretics, violators of public roads, forgers of papal bulls, and counterfeiters of coins.” After a siege of the town undertaken with allies from Rieti, Alatrin, a papal chaplain and rector of the duchy of Spoleto, met with Miranda’s leaders and other witnesses called by a herald to the Church of Saint Mary in Terni. He received their surrender on the pope’s behalf, taking the commune under the direct lordship of the Roman church.66 In September 1231, Gregory issued the first of several warnings to Ezzelino da Romano, the father of the young warlord by that same name, calling him a “public protector” of heretics and causing an “enormous scandal in the general church.” The pope recounted his personal meeting with the senior Ezzelino years before, during his legation in Lombardy in 1221, which led to a tearful scene when Ezzelino deceitfully declared his devotion to the church and hatred for the “heretical depravity.” Gregory gave him two months to appear at the curia to answer for such charges and show his obedience to the church’s commands. Otherwise, the pope would call upon the faithful to take actions against him, including occupying his lands and seizing his goods.67 The Roman pontiff’s support for the preachers of the Great Devotion—whose message of peacemaking included sermons against heresy and, on occasion, the burning of heretics—might have stemmed in part from his interest in opposing heresy through cities and communities of northern Italy.68
As the occupant of the Apostolic See, the pope’s duty to oppose heresy extended beyond the Papal States and Italy. In principle, it reached throughout the universal church, wherever heretics might be lurking among orthodox Christians. In 1231, Gregory forwarded copies of both his and the Roman senator’s antiheretical edicts to other communities outside of Italy, calling upon prelates to publicize solemnly their contents once a month in their dioceses and to make sure that local secular judges and officials implemented and enforced those regulations.69 The pope’s widely circulated calls for action against heretics, bulls like Illi humanis generis and Vox in Rama, painted a vivid portrait of heretical communities gathered in secret for foul rites, such as holding orgies, worshipping black cats, being visited by a diabolic “pallid man,” and tossing the Eucharist in the privy after mass, among other foul deeds.70 To prosecute the war on heresy, Gregory, rather than just relying upon poorly trained or lukewarm local bishops, authorized figures such as the Premonstratensian canon Conrad of Marburg to take the lead in searching for heretical communities. Above all, he turned again to the mendicant orders, the Franciscans and especially the Dominicans, whose commitment to fighting heretics had started with their founder.71 Although the papal curia did not direct the daily activities of their investigations, such inquisitors publicly embodied papal authority, displaying letters and “written mandates” bearing the seal of the Apostolic See that empowered them to act in towns, cities, and parishes throughout Europe.72
As part of this campaign against heresy, Gregory publicly validated the antiheretical measures promoted by Frederick II, which were enshrined in the emperor’s coronation oath and the Constitutions of Melfi. Richard of San Germano describes how the emperor sent his marshal and the archbishop of Reggio to seek out Patarenes in Naples in February 1231, at the same time that Pope Gregory had discovered them in Rome. In 1232, the emperor issued additional bans against heretics in Lombardy and the Regno along with legislation for the suppression of heresy in Germany, relying much like the pope on members of the Dominican order to abolish the “new and unheard-of infamy of heretical depravity” that had arisen there.73 Proclaiming his own duty to destroy heretics, Frederick turned to the language of the two swords to elaborate how the empire and the church worked as separate but complementary entities for the defense of the faith. Writing directly to Pope Gregory, he celebrated how the “heights of heavenly counsel” had ordained the “priestly dignity” and “royal rank” for the rule of the world, disposing the spiritual sword to the one and the material sword to the other for the correction of errors in a time of growing malice and superstition among men. In each region of the Regno, he specified, a bishop would team up with an imperial justiciar to investigate possible heretics, keeping careful records of their findings. Just as the pope summoned the secular arm to assist the church, Frederick called upon the Roman pontiff, through his prayers and advice, to support his efforts against the “insanity of heretics,” together turning the “judgment of both swords, whose power is given to you and us by divine foresight” against those who “arrogantly assume glory for themselves from their perverse dogma, in contempt of the divine power against the mother church.”74
Gregory, in turn, celebrated the emperor’s role in such “pious work,” noting that both the material and spiritual swords had to work together to eradicate the heretical threat. This included groups like the Stedingers, rebellious peasants in the diocese of Bremen whose secret machinations had burst into the open when they attacked clergy, refused to pay tithes, and destroyed churches, causing a “scandal” in Germany. Channeling the language, symbols, and material and spiritual benefits of crusading, and following in the footsteps of his predecessor Innocent III, who had declared the Albigensian Crusade against supposed Cathars, Gregory authorized the preaching of armed campaigns against such enemies of the faith. In addition, the pope promised the same remission of sins to those who took up the cross to combat heretics as those going overseas and taking them under the special protection of the Apostolic See like other crusaders.75 Sending a version of Vox in Rama to Frederick in 1233, the Roman pontiff called upon the emperor specifically to destroy such enemies through the power given to him and avenge the injuries done to Christ the Lord. “Stand forth for the eradication of that depraved and perverse people, who cast so many insults at the living God,” Gregory exhorted the emperor, asking him to assure that the princes of Germany would take up the sword and wipe out the “ferment” of heretical depravity.76
Much like the crusades, the fight against heresy enabled a public conjuncture of the papal and imperial offices. During their period of reconciliation after the War of the Keys, Gregory and Frederick found themselves in a position to turn their energies toward the suppression of heretics, whose crimes threatened the Roman church and empire together and therefore constituted a form of treason. At the same time, again much like the crusades, the alignment of church and empire against heresy went only so far. Under certain circumstances, the pope and emperor could pivot and accuse each other of failing to defend the faith from heretics, a lapse in the duty of their office. In July 1233, praising Frederick’s diligent opposition to heresy in the Regno, the pope felt it necessary to warn him about the scandal he might cause and the damage he might do to the imperial dignity if he burned rebels against his authority under the pretense of punishing heretics.77 Years later, complaining about rampant heresy in Lombardy, the emperor would accuse the pope of favoring and protecting heretics rather than suppressing them. During the course of Frederick’s first excommunication, Gregory had hinted of the possibility that the emperor might himself be guilty of heresy by despising the Roman church’s “power of the keys,” a charge difficult