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 English chronicler Roger of Wendover pictures a “great motion throughout the world for the work of the cross,” especially among “the poor.” Authorized crusade preachers, bearing “written mandates” from the pope, did not have a monopoly on proclaiming the Lord’s wishes for a new crusade. Roger also describes a fisherman who saw a vision of Christ’s body with bloody wounds, pierced by the nails and lance from the crucifixion, who told everyone in the local marketplace about this miraculous sign.15
During the first few months of his papacy, therefore, Gregory’s desire to destroy Frederick seems nowhere in sight. Writing to the emperor on 22 July 1227, just before Frederick’s planned departure on crusade, Gregory struck a pastoral—if, perhaps, paternalistic—tone. The pope offered an exegesis of sorts on the five insignia of the Christian imperial office, including the relics of the cross and holy lance, the triple crown, the scepter for the right hand, and the orb for the left. All of these symbols served as reminders of Frederick’s duty and devotion to Christ: the cross, of the Lord’s suffering; the lance, of the blood that poured from his side; the triple crown, denoting grace, justice, and glory, of Frederick’s crowns in Germany, Lombardy, and the imperial one bestowed upon him by the pope; the scepter, of earthly power to punish the wicked; and the orb, of dispensing mercy. In closing, Gregory stressed his past affection for the emperor and his present concern for his eternal salvation. On the eve of Frederick’s planned departure for the Holy Land, the pope sought to valorize rather than undermine the imperial office, as long as its present occupant remembered the true nature of his calling in the service of the Lord.16
Various chronicles relate how a large crusading force gathered at Brindisi in July and August to await passage overseas. They also describe how the summer heat, spoiled food, and disease took a terrible toll on the soldiers camped outside the city. Some of the troops returned home, while others waited for transport as August turned into September. Frederick numbered among those who fell ill; Ludwig, landgrave of Thuringia, died of sickness. After an aborted attempt to set sail for Syria, the emperor