Gregory felt himself by stern necessity compelled to compass the destruction of the Hohenstaufen,” Ernst Kantorowicz writes. “He seized the first opportunity of compelling the foe to fight.” Others offer similar appraisals. For Gregory, who “knew little of conciliation or peace,” Thomas Van Cleve claims, “the crusade per se was far less important than it had been to Honorius III. It was, indeed, secondary to a much more ambitious goal: the complete triumph of the papacy over the Empire in the struggle for predominance in Christendom.” Or, as David Abulafia puts it, Gregory was “keen to indicate from the start the absolute primacy of his office over that of the emperor…. With his election, cooperation between the pope and emperor gave way to the idea of the subordination of emperor to pope.”2
And yet, judging by Gregory’s repeated declarations and actions, the crusade mattered immensely to his conceptualization of the papal office, forming a public red line between him and the emperor. After generations of summoning crusades, the Roman church had invested vast amounts of spiritual, political, and material capital in the unrealized goal of defeating the so-called Saracens and securing the holy places once and for all. As seen above, during his time as a cardinal legate, Hugolino dei Conti had devoted himself to the project of freeing Jerusalem. As pope, he became responsible for crusading at an especially critical juncture in its history, when disappointment and anxiety about crusading failures reached new levels due to the collapse of the Fifth Crusade. As his predecessor Honorius had warned Frederick and other notable figures on more than one occasion, the Christian people “murmured,” “clamored,” and made “public complaints” about the failure of their leaders to take up the business of the cross and work together to free Christ’s patrimony. Now Gregory faced those same outcries. The need to find a solution to Jerusalem’s captivity had never been greater, or at least, not so acute since the recapture of the city by Salah al-Din two generations earlier.3
In the ensuing struggle between the pope and the prince, communicating the causes and significance of their confrontation to the wider community created its own kind of battlefield, a means to isolate and pressure one’s opponent by denying him moral and material support. Letters from the papal curia and imperial chancery circulated around Christendom, each side trying to generate sympathy for its cause.4 Outside of official channels, rumors spread about the pope’s decision to excommunicate the emperor and about the sensational events of Frederick’s crusade. Once in motion, the confrontation between the two men escalated in ways that neither side could have anticipated, as a shockingly violent battle unfolded for control of the Regno. For contemporaries, these events provoked consternation and amazement, a sense of calamity in their world and uncertainty about how to restore the proper balance between the two powers.
Figure 2. A lead papal bull of Pope Gregory IX. Courtesy of the Portable Antiquities Scheme.
The Delayed Crusade
By the time of Gregory’s election as pope, Frederick’s crusading plans had undergone many twists and turns since he had renewed his solemn vow in Hugolino’s presence seven years earlier.5 These developments set the stage for his subsequent confrontation with the pope. After Frederick’s imperial coronation in 1220, Honorius III had set and reset deadlines for his passage, threating him with excommunication if he failed to leave but reluctantly granting him extensions when circumstances—such as a rebellion by his Muslim subjects on the island of Sicily—forced him to delay his departure.6 The pope even helped to broker a marriage between Frederick and Isabella of Brienne, daughter of John of Brienne, the Latin king of Jerusalem.7 Frederick’s vow, Honorius reminded him, represented more than a private commitment: it was a public obligation that had been renewed on multiple occasions before lay and clerical witnesses. On 25 July 1225, in the presence of two papal legates—Jacob Guala, cardinal priest of San Silvestro e Martino, and Pelagius, cardinal bishop of Albano and former legate on the Fifth Crusade—Frederick had yet again “publicly” renewed his crusading vow at San Germano by swearing on the Gospels and setting a departure date for mid-August two years later. This time his solemn vow included the crucial stipulation that his failure to fulfill its terms would automatically trigger his excommunication and the interdict of his lands.8
Immediately after his election, Gregory also turned his attention to another major piece of unfinished business from Honorius’s papacy: enforcing a peace agreement between the emperor and the Lombard League, an alliance of northern Italian cities, including Milan, Brescia, Mantua, Treviso, Padua, Piacenza, and Bologna, that opposed the Hohenstaufen ruler’s rights in the region.9 This political protest had turned violent in 1226, when the members of the league blocked Frederick’s planned imperial assembly at Cremona, which had been called to reform the empire, eradicate heresy, and pursue the business of the Holy Land.10 If, however, the rebellious Lombards expected papal intervention on their behalf, they must have been disappointed. Honorius’s commitment to the crusade trumped an alignment of interests between Rome and the Lombard League. The pope and his representatives repeatedly signaled their support for Frederick, who invoked his protected status as a sworn crusader against the Lombards’ “illicit conspiracy.”11 By January 1227, Honorius had formulated written oaths for the Lombards to swear, sign, seal, and forward to all of the concerned parties, including Frederick. Both sides had to commit to keep the peace and forego any further “rancor” toward the other, to restore all captives from their recent fighting, and to revoke all bans and other measures passed during their confrontation.12 The Lombard cities also agreed to provide four hundred soldiers for a period of two years as a contribution to the upcoming crusade. The rectors of the league dragged their feet and did not return the signed agreements by the required February deadline. Honorius had to write to them weeks later, insisting that they send the required documents and expressing skepticism about their lame excuse that one of their envoys had dropped the pages into the water during their transport, rendering them illegible. The pope died shortly after sending this letter.13
His successor took immediate steps to secure the terms of this agreement, being committed to the idea that peace among Christians represented a necessary first step toward a successful crusade. On 27 March, Gregory resent Honorius’s final letter to the Lombard rectors with minor changes, demanding that they send the promised “form of peace” (forma pacis) to him and the emperor as quickly as possible. Failing to do so might give Frederick a reason to delay his departure for the Holy Land, thereby provoking the anger of “God and men” against the Lombards. A few weeks after that, he wrote to the rectors again, observing that several signatures and seals were missing from the letters once they had arrived. For this reason, he had not forwarded the incomplete set of documents to the emperor. In writing and in verbal instructions given to the letter’s bearer, he insisted that the rectors should send new versions of the documents with all of the appropriate seals. They also needed to ready the soldiers they were supposed to contribute in support of the upcoming crusade, as required by the terms of the recent peace agreement. If necessary, the archbishop of Milan would compel them to fulfill their obligations by ecclesiastical censure.14
In April, the pope announced the successful resolution of the conflict between Frederick and the Lombards to the archbishop of Cologne and prelates throughout Germany, calling upon them to instruct all of the sworn crusaders in their dioceses to ready themselves for the upcoming passage overseas. Crusade preachers, authorized by Honorius before he died, had been laying the groundwork for the campaign for months. Like every crusade before it, appeals for this latest expedition drew more enthusiasm from some corners of Europe than others, as the expedition faced shortages of manpower and financial means, stragglers, and reluctant crusaders. English monastic histories such as the Waverley Annals remember an outpouring of enthusiasm in England for this armed journey to the holy places, recording that people “inspired and strengthened by apostolic letters and advisements, signed and armed besides by the virtue and wood of the holy cross, desired to go forth to avenge the injuries done to God by the enemies of the Christian name.” In his Flowers of History, the
