By this time, Gregory had begun to look beyond such epistolary denunciations, legal threats, and “spiritual” weapons, extending papal sanctions into the realm of armed conflict with Frederick’s supporters on the Italian peninsula. Over the course of the winter, he started to coordinate the assembly of what chroniclers called a “papal army,” or the “army of the lord pope.” As the pope’s biographer describes his decision, “since the punishment of the spiritual sword did not chasten the sinner, overcome by necessity, the successor of Peter took the step of wielding the temporal sword.”67 Acting in his capacity as the lord of the Papal States, Gregory fielded this force with the help of John of Brienne, Frederick’s former father-in-law and a papal rector since 1227, along with John de Colonna, cardinal priest of Santa Prassede; Pelagius of Albano; and the papal chaplain Pandulf, who was “experienced” in military affairs. By the spring of 1229, this army, deployed as three smaller units, had pushed the emperor’s vassals and allies from Ancona, Spoleto, and Campagna and began advancing into the Regno.68
When they talk about it at all, historians typically call this conflict the War of the Keys, named after the symbol featured on the papal army’s banner. Discussions about this campaign typically revolve around the question of where it fits in the trajectory of so-called political crusades, in other words crusading campaigns called for the primary purpose of defending papal territories or subduing papal enemies within Europe.69 The general consensus seems to be that the War of the Keys was a kind of “half” or “quasi” crusade authorized by the pope, promoted much like a genuine crusade but lacking important elements of “true” crusading, including the promised remission of sins for combatants—at least not until the closing stages of the conflict—and the actual use of the cross as a martial sign.
Clearly, the difference between symbols such as the cross and the keys made an impression on contemporaries like Richard of San Germano, who describes in his chronicle a pitched battle between a “crusader army” (crucesignatorum exercitus), a designation for supporters of the emperor who had recently returned from Syria while still bearing their crosses, and the pope’s “keysader host” (clavigeros hostes).70 For contemporaries, however, the controversy caused by the War of the Keys did not revolve around the question of whether the battle against the emperor constituted a crusade or not. It centered on a different issue—whether the pope possessed the legitimate right to wield the “material sword” (gladius materialis), as well as the “spiritual sword” (gladius spiritualis). Recent generations of theologians and canon lawyers had debated the exegesis of the “two swords” (Lk 22:38): Did God bestow each sword directly to its bearer, the emperor and the pope, the principal representatives of the two powers? Or did God grant both swords to the pope, who then delegated the material sword to the emperor to wield in defense of the church? Canon lawyers, in their glosses, offered a wide variety of opinions on the matter. Regardless, in either scenario the pope did not wield the material sword directly—the power of armed force, coercion, and punishment—but delegated its use to secular rulers, lay people who were not constrained by the clerical prohibition of bloodshed.71
When Gregory called for the raising of a papal army, the political theology of the two swords moved from canon law commentaries into the public eye as the pope sought to secure material support for his campaign. Deploying the material sword in defense of the church did not come cheaply. Facing an insufficient supply of local troops from the papal patrimony, Gregory appealed for aid from communities, clergy, and rulers around Europe, including the king of Sweden, the rectors of the Lombard League, and the Portuguese prince, Peter. In his Flowers of History, Roger of Wendover describes how Gregory’s legate Master Stephen arrived in England to collect one-tenth of the kingdom’s “moveable property,” clerical and lay, “for his war undertaken against the Roman emperor.” Gregory’s “apostolic letters sent through various part of the world” enumerated the many reasons why he took this action, including all of Frederick’s misdeeds while on crusade, his plunder of the military orders’ properties in the Regno and overseas, his disregard for the church’s interdict, and more. “For these causes,” Roger writes, “the lord pope went to war against him, asserting it was just and necessary for the Christian faith for such a mighty persecutor of the church to be cast down from the imperial dignity.” During an assembly called by King Henry III at Westminster, Stephen, bearing Gregory’s “written authorization,” read the pope’s letters aloud, spelling out the papal demand for a special tax to sustain his war against the emperor.72 Some of these written appeals survive in a register of letters, charters, and other documents from Salisbury, revealing how the pope pitched his war against Frederick as the response to a “common danger,” insisting that a threat to the “head” of the church represented one to the “entire body.” For these reasons, Gregory wrote, “we have begun to exercise the temporal power, gathering many armies with ample stipends for this purpose, for such possessions ought not to be spared, when the church is universally and bitterly assailed.”73
These letters provide a striking example of the pope’s unique public standing as the figure who could call for armed Christian action on behalf of the entire church as a “common” enterprise and a shared responsibility, summoning leaders to defend “the papacy and Saint Peter’s regalia” and to fight “for the Lord under his commander Saint Peter” against the excommunicate emperor, who was a predator of churches, abuser of clergy, and friend to the infidels.74 Gregory’s unusual and to some extent unprecedented measures on behalf of the Apostolic See also remind us about the hard limits to the pope’s actual reach. Assembling such armies always represented an ad hoc logistical affair that was constrained by financial limits, insufficient numbers, and uneven enthusiasm from the vassals, friends, and family members who comprised a typical medieval army. Gregory’s papal army was no exception.75 Judging by the pope’s calls for the Lombards to fulfill their obligations to the church, the rectors of the league did not provide as much assistance as the pope would have liked. They did send troops, but not enough. Gregory also complained about their late arrival, about their lack of funds, arms, and horses, and about the fact that some of the levies were already planning to head home. He even forwarded them dispatches from the front lines, written by John of Brienne and John de Colonna and affixed with the papal bull, testifying to the desperate need for help.76
According to Roger of Wendover, the Apostolic See’s demands for a direct tax to pay for the papal army—the first of its kind—met with reluctance and public protest. Realizing that Henry III would not prevent the pope’s exactions, the English earls and barons emphatically refused to pay the tithe. After debating among themselves, the clergy decided to pay the demanded one-tenth, in part anxious about the legate Stephen’s express power to excommunicate those who refused to render the funds or colluded to commit fraud in their collection. The pope’s representative also had the right to demand that clerics swear an oath on the Gospels to make their payments, that they record the amounts on their “rolls” with seals affixed in testimony, and that they agree to censure anyone caught impeding the payments. Roger writes that the clerics in question had to pawn all sorts of sacred vessels and liturgical objects to meet the demands of such an unprecedented exaction. In this regard, the English clergy seemed less concerned with the pope’s right to fight a Christian emperor in defense of the church than they were with how he planned to pay for it.77
Others challenged and denounced Gregory’s decision to authorize armed force against the emperor. In a letter sent to Frederick during his stay in Syria, his bailiff Thomas of Acerra expressed astonishment that the pope, the emperor’s “public enemy,” had “decreed contrary to Christian law to vanquish you with the material sword, since, he says, he is unable to cast you down by the spiritual sword.” Thomas asserts that Frederick’s allies, especially among the clergy, could not believe that the “Roman pontiff could do such things, taking up arms against Christians, especially since the Lord said to Peter ‘put your sword in its scabbard, for all those who strike with the sword, shall perish by it.’ ” They wondered by what right the pope acted, excommunicating thieves, arsonists, and murders on the one hand and then turning his authority to such ends on the other.78 Chroniclers expressing