The War of the Keys (1228–1230) was the first military conflict between Frederick II, Holy Roman Emperor, and the Papacy. Fighting took place in central and southern Italy. The Papacy made strong gains at first, securing the Papal States and invading the Kingdom of Sicily, while Frederick was away on the Sixth Crusade. Upon his return, he defeated the papal forces, forcing Pope Gregory IX to begin peace talks. After drawn-out negotiations, the treaty of San Germano terminated the conflict with no territorial changes.
The causes of the conflict lay in conflicting papal and imperial claims in central Italy, Frederick's failure to fulfill his agreement to lead a crusade on schedule and his supposed mistreatment of the Sicilian church. The emperor was excommunicated before he left on his crusade in June 1228. His representatives, with or without his permission, entered territory claimed by the Papacy and Gregory responded with war. His aim was to take Sicily, which was a fief of the church, back from Frederick.
Gregory raised troops and funds internationally, from as far afield as Portugal and Sweden. He sent two armies under the command of John of Brienne into the disputed territory in late 1228 and another army into the Kingdom of Sicily in January 1229. The war was going in his favour as late as May, but he was running low on funds and troops. The strategy of denying the ports to Frederick failed. The return of the emperor in June quashed the rumours spread by papal agents that he was dead and caused a rapid reversal of fortunes. The sieges of Sulmona and Capua were lifted by September and by October most of the kingdom had been recovered. Negotiations were opened in November and the active phase of the war ended.
Principal sources
The principal sources on the war are in Latin. The Chronica of Richard of San Germano, which has a pro-imperial stance, is one of the most important narrative sources. The biography of Gregory IX in the Liber censuum provides a valuable pro-papal narrative. Other important chronicles are Roger of Wendover's Chronica sive flores historiarum and the Chronicon of Aubry of Troisfontaines. From a crusader perspective the war is covered in the Colbert–Fontainebleau Eracles and the Chronicle of Ernoul and Bernard the Treasurer.
There are three north Italian chronicles that cover the war from the contrasting perspectives of the pro-papal Guelphs and pro-imperial Ghibellines. From the Guelph perspective are the contemporary Annales placentini guelfi of Giovanni Codagnello and the Chronicon faventinum, while the Ghibelline perspective is represented in the slightly later Annales placentini gibellini. Even the Guelph chronicles, however, do not exactly toe the papal line. They generally view the war as the fault of Frederick for refusing to respect papal territory, but do not blame the emperor for delaying his crusade.
The most important documentary source is the register of Gregory's letter's, which are edited in the Monumenta Germaniae Historica. Letters to and from Frederick also survive, including two of his that were copied into an Arabic chronicle, the Taʾrīkh al-Manṣūrī of Ibn Naẓīf al-Ḥamawī. For the peace negotiations, the letters to and from Cardinal Thomas of Capua are a critical source.
An important source for contemporary critical attitudes towards the pope's war is the work of the troubadours, lyric poets writing in Old Occitan.
Background and causes
The main points of contention between Frederick and the Papacy were the crusade and the Papal States. Frederick had vowed several times in public ceremonies to lead a crusade to the Holy Land on pain of excommunication. Yet Pope Honorius III had granted him many delays. Frederick finally sailed from Apulia in August 1227, but almost immediately turned back, claiming illness. Gregory IX was not prepared to accept another delay. He accused Frederick of faking his illness (although the Guelph annals accept the excuse). On 10 October 1227, Gregory excommunicated Frederick. The Annales placentini guelfi identifies the harm Frederick's delay caused the crusaders who had gathered in Apulia as one of the causes of the war.
In March 1228, Gregory renewed the excommunication and ordered Frederick to stop attending religious services. Otherwise, Gregory would absolve his subjects of their oaths of fealty to him and confiscate the Kingdom of Sicily, which was a papal fief since 1059. The popes also claimed that the march of Ancona and duchy of Spoleto belonged to them, but Frederick refused to relinquish imperial control. He appointed Rainald of Urslingen as duke of Spoleto.
In November 1225, Frederick II had married the thirteen-year-old queen Isabella II of Jerusalem, thus depriving her father, John of Brienne, of the regency. Although John refused an offer to lead the Lombard League in its rebellion against Frederick while Isabella was alive, the queen died in May 1228. Still excommunicated, Frederick II left on the Sixth Crusade at the end of June. Gregory did not recognize the expedition as a crusade. With no reason any longer to keep on good terms with Frederick, John accepted command of the papal army preparing to invade Sicily. The absence of the emperor on crusade provided the perfect opportunity and, in August, Gregory released both Frederick's imperial and Sicilian subjects from their oaths of obedience. Gregory intended to replace Frederick as emperor. Although Frederick believed that Gregory also wanted to replace him on the Sicilian throne with one of his pliable young sons, the pope intended to dissolve the kingdom and rule it directly through papal governors.
The war against Frederick began while he was still in the east. In March 1229, he signed a treaty with the Ayyubid sultan al-Kāmil by which he took control of Jerusalem and brought his crusade to a successful conclusion. In July, Gregory published an encyclical denouncing the treaty and Frederick as un-Christian.
Papal war planning
Gregory's call for support, both in men and money, was international. He issued a bulletin to his legates and commanders on 1 December 1228 detailing his plans for raising troops and funds.
Forces
Sources generally refer to the pope's forces as the "papal army" or "army of the lord pope". Gregory himself called it the "army of the church" (exercitus ecclesie) and in one instance the "army of Christ". Richard of San Germano describes the papal army as "enemies bearing the sign of the keys" (clavigeros hostes) and clavesignati ('key-signed'), a play on crucesignati (cross-signed), which was the common term for crusaders. These are references to the insignia of the keys that appeared on the papal banners. The keys were also apparently sewn onto clothing over the breast in imitation of the cross borne by crusaders. The conventional name "War of the Keys" is a reference to this insignia. It has been favoured by scholars "because it embodies the quasi-crusade status of the campaign".
The papal army contained both knights and infantry. It was mostly raised in the Papal States and in Tuscany. These, however, could not supply a large enough army for Gregory's purposes, and so he sought to raise troops abroad. He sent requests throughout the Holy Roman Empire: to the German princes, to the Lombard League and to the Republic of Genoa. He also came to employ many mercenaries from France, England and Spain. Bishops Milo of Beauvais and Hugh of Clermont brought troops from France. That a few Germans heeded the pope's call is known from the fact that Frederick later pardoned them. Gregory was still trying to raise troops as late as June 1229, when he asked the infante Peter of Portugal to bring knights to Italy to fight Frederick. The army of 1228 was deployed in three units against Ancona, Spoleto and the Campania. On 21 December 1228, when Gregory wrote to King Eric XI of Sweden requesting financial aid, he confirmed that his forces were already divided into three armies.
The papal commanders were John of Brienne, Cardinal Giovanni Colonna, Cardinal Pelagius of Albano and the papal chaplain Pandulf of Anagni, acting as papal legate. John is sometimes seen as the overall commander of the papal forces, but this is not clear from the sources. He was joined by his nephew, Walter IV of Brienne, who claimed the principality of Taranto and the county of Lecce in the Kingdom of Sicily. His northern army facing Ancona had the more urgent task, but the southern army facing Sicily under Pandulf seems to have been the main force. The southern army was drawn mainly from the Papal States. It also contained many Sicilian exiles and was even captained by two, counts Thomas of Molise and Roger of Aquila. These two armies are easily identified through the sources. They are the second and third, but of the first army mentioned by the pope no details or names of commanders have come down.
Finances
The bulletin of 1 December 1228 contains the earliest reference to papal fundraising for a war against Christians. Since Gregory did not initially call a crusade against Frederick, he could not offer indulgences to those who took part in the war or gave money. The use of direct taxation to fund a papal army was a "first of its kind". He levied tithes, the so-called "crusade tenth", from France, England, Wales, Scotland, Ireland, Denmark, Sweden, northern Italy and eastern Europe. In France, the remainder of a five-year levy first collected in 1225 for the Albigensian Crusade of 1226 was set aside for the new war after the crusade ended with the treaty of Paris in April 1229. In total, about 100,000 livres tournois were received from France. The tithe was successfully collected in northern Italy and eastern Europe, possibly in Sweden, but not in England or Scotland.
According to Roger of Wendover, the tithe was strongly resisted in England. He says that the pope levied the tithe on all the "moveable property" in the kingdom, both secular and ecclesiastical. Stephen of Anagni was named collector (and possibly legate) for England, Scotland and Ireland on 23 December 1228. King Henry III of England called an assembly of the realm for April 1229 at which Stephen read out the papal letters. There were public protests against the exactions. When it became clear that Henry III would not interfere with Stephen's mission, the higher nobility simply refused to pay. According to Roger, Gregory rewarded Henry by blocking the election of Walter d'Eynsham as archbishop of Canterbury. To meet the pope's demands, many prelates pawned their plate and their vestments, fearing Stephen's power to excommunicate nonpayors or those who defrauded the Holy See. Stephen was also empowered to demand that clergy swear oaths on the Gospels that they had paid their share and to affix their seals to the records of payment. According to William of Andres, the total collected in England was 60,000 marks. Gregory was still waiting for it in June 1229. There was also resistance to the tithe in Scotland. According to the Scotichronicon, when Stephen attempted to execute his commission in Scotland in early 1229, he was denied entry by King Alexander II.
Lombard League
The north Italian cities of the Lombard League were Gregory's most natural allies against Frederick. Records of the deliberations of the rectors of the league concerning the War of the Keys do not survive. Examples of such deliberations, however, do appear in the Dictamina rhetorica of Guido Faba of Bologna, composed around 1230. They likely reflect actual debates. The rectors met with the pope in September 1228 and agreed to supply troops to defend the church.
The troops sent were not as many as Gregory had requested or perhaps as they had promised, nor as fast. If the details in the Dictamina rhetorica are accurate, the league promised 500 knights by January 1229. In February 1229, Gregory renewed his appeal through the legate Goffredo of San Marco. The Annales placentini guelfi confirms that the troops were delayed. According to the Annales placentini gibellini, the cities collectively supplied 300 knights to Giovanni Colonna. The specific contributions of two cities are known. The Annales placentini guelfi records the late arrival of 36 from Piacenza in March 1229 and the Chronicon faventinum records that Faenza contributed 27 knights. Nevertheless, Gregory complained that the league's troops were deficient in money, weapons and horses. He was still demanding the fulfillment of the league's obligations in May 1229.
The Annales placentini gibellini records that the north Italian troops began returning home after learning of Frederick's landing at Brindisi in June 1229. This is confirmed by a letter of Gregory's of 26 June. The pope also confirmed shortfalls in their wages. On 13 July, Gregory demanded three more months of service from those troops that had already arrived. He also demanded reinforcements and money under pain of excommunication. He forwarded to the rectors the dispatches of John of Brienne and Giovanni Colonna, sealed with the papal bull, to demonstrate the army's desperation. The Lombard cities, however, were by then distracted by their own civil war, which culminated in the battle of San Cesario in August 1229.
Germany
Gregory IX sought to depose Frederick II as Holy Roman Emperor and engineer the election of a new emperor. Roger of Wendover records that the pope sent letters to the German princes to justify that Frederick "be cast down from the imperial dignity". He cites a letter to Duke Leopold VI of Austria dated 18 July 1229. These plans had to be abandoned, however, when among the German princes only Duke Louis I of Bavaria showed any interest in going to such an extreme.