the Western empire to the Roman pontiff. A concluding scene shows Sylvester on horseback while Constantine humbly acts as his groom. By visualizing the past in this manner, the frescoes communicate a message about the proper relationship between the “two powers,” that is, between the spiritual authority of priests and the temporal might of secular rulers, embodied above all by popes and emperors. As the example of Constantine and Sylvester revealed, emperors should ultimately defer to popes, recognizing their superior form of sacerdotal sovereignty.1
Outside the walls of the chapel, when its frescoes were new, Christians faced a far more turbulent relationship between the chief representatives of the two powers: a violent division between Pope Innocent IV and the Hohenstaufen emperor, Frederick II. Contention between the papacy and the imperial ruler had begun under Innocent’s predecessor, Gregory IX, who excommunicated Frederick not once, but twice: for the first time in 1227, when the emperor failed to depart on crusade by an agreed-upon deadline, and again in 1239 (nine years after their previous reconciliation), when he was accused of various sins, crimes, and abuses of the church. The two had remained fiercely at odds when Gregory died in 1241. After his election one and a half years later, Innocent seemed poised to make peace with Frederick until negotiations between them collapsed and he fled to the city of Lyons. In July 1245, at the Council of Lyons, the pope deposed the Hohenstaufen ruler from his kingdoms and honors, a judgment rejected by the emperor as an illegal act of papal overreach into temporal affairs. Intensifying conflict between the two sides followed for years to come. In 1250, unrepentant and excommunicate, Frederick died while still warring with the pope. Returning to Italy, Innocent spent the remainder of his life fighting with Frederick’s heirs, until his own demise at Naples four years later.
Figure 1. The Donation of Constantine. Basilica of Santi Quattro Coronati, Rome. Getty Images.
Reading many of Frederick II’s modern biographers, one gets the unmistakable impression that Gregory and Innocent in turn shared a deep-seated desire to destroy the emperor, viewing him as the principal danger to the papacy’s territorial possessions on the Italian peninsula and their main competitor for universal sovereignty over Christendom.2 Although such histories of the Hohenstaufen ruler are in many cases decades old, they continue to cast a long shadow over Gregory and Innocent, in part due to the lack of recent book-length studies on the two popes.3 Perhaps not surprisingly, Frederick emerges as the clear protagonist in such works. While the emperor has enjoyed the reputation of being an iconoclast and a modern man born before his time, his papal opponents seem eminently “medieval” by comparison, that is to say, intolerant, narrow-minded, and determined to realize their theocratic aspirations at any cost. Desperate to eradicate Frederick, Gregory and Innocent squandered the church’s wealth, discredited the crusades by turning them against their foe, and damaged their office’s moral standing, setting the papacy on the slow road to decline and near ruin in the later Middle Ages.4
In this book, I retell and reevaluate the history of Gregory IX and Innocent IV’s combative relationship with Frederick II from a different perspective: that of the medieval public. To influence, restrain, and combat the reigning emperor, the two popes had to convince the Christian community about the legitimacy of their cause, including not only kings, archbishops, and other highly placed elites but also members of the lesser clergy and lay nobility, crusaders and mendicants, merchants and burgers, and parish priests and their parishioners, among others. The papal confrontations with the Hohenstaufen ruler took place not just on the level of high politics and diplomacy but also in city streets, ports, plazas, and other open spaces. The battles between the popes and the prince could be heard in the proclamation of excommunications, the preaching of sermons, or the contrary silences imposed by interdict. Chroniclers with their own stakes in the outcome memorialized the clash between the papacy and empire in their historical writings, leaving traces of wider reactions to the turmoil disrupting their society: the circulation of wild rumors, the clamoring of the people, and the awe caused by apocalyptic signs of a world in crisis. Nothing less than the fate of Christendom seemed to hang in the balance between the discordant two powers.
The point of this study is not to turn the tables on Frederick, making Gregory and Innocent into heroes of the story, the emperor into the villain. Scholars with confessional sympathies have tried this before with equally skewed results.5 In the pages below, however, I devote the majority of my attention to the means of communication, documentary culture, performances, and media that turned the papacy’s spiritual and sacramental authority into consequential forms of social and political action.6 While highlighting the papal side of the epoch-making struggles between the two powers, I also keep a close eye on Gregory and Innocent’s other shared commitments, including their widely publicized mandates to create peace in Christendom, to promote crusading, and to eradicate heresy from the church. Those projects for the common good of Christendom, as the two popes presented them, shaped their response to Frederick’s imperial reign, not the other way around. Ironically, perhaps, given the assumption of irreconcilable differences between him and the two popes, Frederick shared many of those same goals, albeit with his own ideas about how to realize them. In many ways, the popes and the prince disagreed so publicly and so violently because they agreed on so much.
By taking such an approach to the subject, this book seeks to restore a sense of contingency to the history of the thirteenth-century struggles between the papacy and empire, rather than viewing them as a more or less inexorable outcome of opposing political ideologies. Theoretically supreme in the theological and juridical realms, the bishops of Rome faced constant and unexpected challenges, constraints, and limitations to the enactment of their priestly sovereignty in the public realm. No one must have understood this better than Gregory and Innocent. Their contentious relationship with Frederick forced them to intervene in European politics and society in far-reaching and controversial ways, publicizing his excommunicate and eventually deposed status, attacking his reputation through propagandistic letters, deploying papal legates to act against his interests, declaring crusades against him, and transferring vast sums of ecclesiastical wealth to support the papacy’s allies against Frederick’s supporters. The results of those efforts remained imperfect and reliant upon forces that the popes could not easily or always control. Innocent, tellingly, was not on hand to see the frescoes of Sylvester and the deferential Constantine unveiled in Santi Quattro Coronati. He remained in exile at Lyons, unable to return to Italy for as long as Frederick lived and his allies dominated the road to Rome.
To a considerable extent, the history of Gregory IX and Innocent IV’s battles with Frederick II remains inextricably bound to the larger question of the medieval “papal monarchy.”7 The term papal monarchy is a compelling and evocative one, but in some ways misleading—even in the Middle Ages, popes did not rule like kings over the faithful. In its technical, juridical sense, the concept of the papal monarchy denotes the pope’s “fullness of power” (plenitudo potestatis) over the church and its offices, his position atop the ecclesiastical hierarchy and status as the final arbiter of canon law, able to grant dispensations, definitively settle disputes, and decide legal cases.8 Used in a more capacious formulation, accurately or not, the papal monarchy suggests the awesome ambitions of the medieval papacy to stand as the supreme sovereign of Christendom, asserting the ultimate superiority of the priesthood (sacerdotium) over temporal rulership (regnum). Starting with papal reform movement of the eleventh century, building momentum in the twelfth century, and peaking in the thirteenth, the papal monarchy from this vantage point instantiated the ambitions of popes, theologians, and canon lawyers to realize the papacy’s juridical authority over worldly princes of all kinds, thereby creating what has memorably been described as a hierocratic vision of the Christian political order.9
As will become evident through this book, theologically inflected legal concepts of sovereignty did indeed play a crucial role in the elaboration of papal claims to wield not just spiritual but also, in exceptional cases, temporal power
