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 to prove and one that the pope did not openly pursue. When he excommunicated Frederick for the second time, this accusation would return with less reticence. For the time being, however, the two powers, wielding the spiritual and material swords, stood united against the common threat of heretical depravity in their midst.
War with the Romans
In May 1234, Frederick made a personal appearance before Pope Gregory, who was then staying at Rieti. During this meeting, they discussed the unsettled conditions overseas in the holy places, but they also spoke about more pressing business. According to the pope’s biographer, Fredrick came as a supplicant, bringing his son Conrad with him and seeking assistance against his other son, Henry, the king of Germany, who had rebelled against his father. Gregory likewise had reasons for welcoming Frederick. Much like the emperor, he faced his own problems with inside agitators who questioned his authority as the lord of the Papal States and bishop of Rome, in this case facing an uprising by the inhabitants of his own city. This meeting at Rieti set the stage for perhaps the most unexpected and understudied episode of public cooperation between Gregory and Frederick during the years after the peace of San Germano, as the two former opponents agreed to assist each other against their present enemies.78
Historians generally view this alliance as one of undisguised convenience: the pope aiding the emperor against his traitorous son, the emperor assisting the pope to wage war against his own city. This convergence of Gregory’s and Frederick’s interests, however, should not be dismissed as merely opportunistic. Much like the papal promotion of other common causes with the emperor, such as freeing Jerusalem and wiping out heresy, Gregory’s turn toward the “material sword” represented an advantage of the peace between the two powers. While the pope mobilized Christians to fight for the common cause of defending the Roman church’s liberty, Frederick could fulfill his imperial duty as that church’s primary defender. To some extent, the war with the Romans validated the harmony between two powers, even if the results of their cooperation fell short of papal expectations. At the same time, Gregory’s war against the Romans with imperial aid raised complaints about the pope’s use of ecclesiastical resources to field a “papal army” on the Italian peninsula. Much like the War of the Keys, the pope’s fight against the Christians of his own city did not sit well with everyone.
Gregory hardly represented the first pope to experience troubles with Roman aristocratic factions and communal government, a problem shared by generations of his papal predecessors. But as Peter Partner observes, his relations with the city were “notoriously bad.”79 As seen in the previous chapter, after the pope repeated Frederick’s sentence of excommunication in the basilica of Saint Peter in 1228, a mob had driven him and several cardinals out of the church and eventually out of the city. By the time that the Gregory and Frederick agreed to the Treaty of San Germano, the pope had more or less made peace with the citizens of Rome, who had been “assailing the churches of the City and harassing the Patrimony’s vassals with various burdens,” as the author of the pope’s vita describes the situation. He also claims that the flooding of the Tiber in winter 1230, clearly a punishment from God, convinced the Romans to change their wicked ways. However, problems persisted between the Roman pontiff and the Romans due primarily to the city government’s territorial ambitions in central Italy. In the spring of 1231, Roman forces attacked Viterbo, part of the papal patrimony, and seized the town of Monteforte, near Naples, the following summer, using it as a base to “subjugate the remainder of Campania to their dominion.” In June 1232, Gregory left Rome for Rieti, not only to escape the summer heat but also because of his growing tensions with the Romans.80
During this episode of conflict with the civil government of Rome, the pope turned to Frederick for help, seeking his assistance against the “pride of the Romans.” At Gregory’s request, the emperor took Viterbo under imperial protection in 1231 and tried to ensure that the Viterbans would cooperate with papal legates assigned to broker a peace agreement, Thomas of Capua and Raynald da Jenne. Throughout his correspondence with Frederick relating to this situation, Gregory emphasized the emperor’s role as the defender and advocate of the Roman church, who was responsible for protecting its rights, which were indelibly linked to those of the empire. At an especially evocative moment, he described his joy that the “imperial right hand” brandished the “triumphal
