Frederick had demonstrated that his overriding priority was the defence, consolidation and expansion of the Hohenstaufen Empire. These were not uncommon concerns for a medieval monarch. The same burdens of crown rule had impacted upon the crusading careers of Henry II and Richard I of England and Philip Augustus of France. Indeed, from one perspective, Frederick’s dedication and determined ambition were commendable. But in the wake of the Fifth Crusade, the new emperor came under mounting pressure to make good his vows and enter the war for the Holy Land. This compulsion derived in part from public opprobrium, but it was driven most forcibly by the papacy. Honorius III was desperately concerned to renew the campaign for Jerusalem’s recovery and assuage his own guilt over the Damietta expedition’s dismal outcome. He also recognised that Frederick, now having encircled the Papal States, posed a clear threat to Roman sovereignty. The crusade might be a useful and effective means of controlling this potential enemy.

Stupor mundi

Frederick II was one of the most controversial figures in medieval history. In the thirteenth century he was lauded by supporters as stupor mundi (the wonder of the world), but condemned by his enemies as the ‘beast of the apocalypse’ today historians continue to debate whether he was a tyrannical despot or a visionary genius, the first practitioner of Renaissance kingship. A paunchy, balding figure with bad eyesight, physically Frederick was rather unprepossessing. But by the 1220s, he was the Christian world’s most powerful ruler: emperor of Germany and king of Sicily.

It has sometimes been suggested that Frederick had a distinctly unmedieval and enlightened approach to governance, religion and intellectual life, and that he brought this revolutionary perspective to the business of crusading, transforming the holy war and Outremer’s fate with a wave of his mighty hand. In reality, Frederick was not quite so radical, either as a monarch or as a crusader. Through his upbringing in Sicily–with its own indigenous Arab population and long-established network of Muslim contacts–Frederick was familiar with Islam: he knew something of the Arabic language, retained the services of a loyal group of Muslim bodyguards and even possessed a harem. He also had an inquisitive mind, an avid interest in science and an absolute passion for falconry. But the notion of maintaining a cultured royal court was far from unique. The Iberian Christian kings of Castile were perhaps even more open to Muslim influence in this period. And Frederick was not always tolerant in his attitude to faith and Christian dogma, violently suppressing Sicilian Arab rebellion between 1222 and 1224 and opposing heretics within his realm.

Contemporaries and modern commentators alike have also alleged that the new Hohenstaufen emperor was distinctly disinterested in holy war. Yet, despite his failure to fight in the Fifth Crusade, Frederick would prove, in time, to be driven by an authentic commitment to the crusading cause. His approach to the struggle for dominion of the Holy Land was conditioned, however, by the firmly held belief that he was destined to extend his imperial authority across all Christendom. By leading a crusade, Frederick sought both to fulfil what he regarded as his natural obligation as a Christian emperor and to exercise his equally innate right to recover and rule the most sacred city of Jerusalem.²¹

Imperial crusader, Jerusalemite king

In the mid-1220s, Pope Honorius III repeatedly sought to bind Frederick to a new crusading pledge. Initially, the campaign was supposed to start in 1225, but by March 1224 the emperor was requesting a further delay because of the ongoing difficulty of maintaining order in Sicily. With the pope’s patience now all but exhausted, a new agreement was formalised at San Germano (in north-western Italy) in June 1225. The treaty contained a number of strict provisions: Frederick was to recruit an army of 1,000 knights and fund their deployment in the Holy Land for two years; in addition, he had to provide 150 ships to transport crusaders to the East and furnish the master of the Teutonic Order, Herman of Salza (a close Hohenstaufen ally), with 100,000 ounces of gold. Most critically, the emperor promised, on pain of excommunication, to set out on crusade by 15 August 1227. Frederick accepted these terms partly because of his own willingness and determination to initiate an eastern campaign, but also to win support within the Hohenstaufen realm for a crusade tax–a levy that was unpopular because many feared, on past form, that its proceeds would end up in the imperial treasury. By agreeing to the Treaty of San Germano, Frederick was signalling categorically that, this time, he would redeem his vows. The move earned him the backing of his subjects, but it also left him tied to a dangerously precise schedule.

By this time the emperor had begun to lay diplomatic foundations for his expedition to the Near East. This brought him into contact with two Levantine rulers–John of Brienne and al-Kamil–both of whom evidently believed that they could manipulate Frederick for their own advantage. They had not counted on his guileful skills as a politician and a negotiator; his remarkable ability to mix pragmatism with resolute force. In the early 1220s John of Brienne still claimed the title of ‘king of Jerusalem’ through his role as regent to his daughter Isabella II, but faced an uphill battle to assert his legitimacy against Outremer’s independent-minded Frankish barons, who by now had become particularly adept at using the laws and customs of the realm to limit royal authority. In 1223 John therefore agreed to a marriage alliance between Isabella and Emperor Frederick, imagining that Hohenstaufen backing would finally cement his own position as king. The union was duly formalised in November 1225 at a ceremony in Brindisi (southern Italy) attended by John and leading members of the Jerusalemite aristocracy. To John’s surprise and disgust, as soon as the wedding finished, Frederick asserted his own rights to direct rule over Frankish Palestine and browbeat the assembled Latin nobles into submitting to his authority. This manoeuvre left John of Brienne disgruntled and disenfranchised, but it also rewrote the rules of crusade leadership–setting the stage for the coming expedition to be directed by an individual who uniquely combined the offices of crusader, Hohenstaufen emperor and Jerusalemite king.

Frederick also established a dialogue with al-Kamil, the Ayyubid sultan of Egypt, around 1226, although it is not clear which side initiated communication. Al-Kamil seems to have been aware of the emperor’s planned expedition and, in order to diffuse any renewed threat to the Nile region, he proposed an unusual pact. Like his father al-Adil before him, the new sultan was far more interested in reaching diplomatic accommodations with the Franks–thereby safeguarding their shared commercial interests–than in waging a bloody and disruptive jihad. Al-Kamil’s position as overlord of the Ayyubid confederation was also under threat in 1226. In the wake of the Fifth Crusade, relations with his brother al-Mu‘azzam, emir of Damascus, had soured, and al-Mu‘azzam had taken the rather drastic step of allying with the Khwarizmians–a band of ferocious Turkish mercenaries, driven out of Central Asia by the advent of the Mongols and now operating from northern Iraq. To balance this danger, al-Kamil invited Frederick to bring his armies to Palestine and, in exchange for a promise of aid against al-Mu‘azzam, offered to return Jerusalem to the Latins. To iron out the details of this groundbreaking agreement, the sultan dispatched one of his most trusted lieutenants, Fakhr al-Din, as an envoy to the Hohenstaufen court. There, he and Frederick treated together on amicable terms, and the emperor even knighted Fakhr al-Din as a sign of their friendship.²²