The Impact of Frederick II on the Crusading Movement

Bust thought to represent Frederick II

Oliver of Paderborn wrote in 1220 that 'the illustrious Emperor and King of Sicily is being eagerly awaited by the people of God for the happy consummation of the enterprise.' Oliver had helped preach the enterprise in question, the Fifth Crusade. He had witnessed its major engagements, from indecisive actions in the Holy Land to the bloody siege of Damietta, which had at last fallen. The Crusaders, including the papal legate Pelagius of Albano, were aware that the newly-crowned Emperor had taken the Cross. They regarded him as the Crusade's natural leader, who would come to lead them south against Cairo, thus depriving the Muslims of the riches of Egypt and facilitating the recovery of Jerusalem - a Jerusalem, as it was hoped, that would no-longer be vulnerable to incursions from the Nile. Seven years later Frederick did embark on Crusade, but by then he was excommunicate and on his way to becoming the object of crusades himself. Perhaps because he acted without Church backing, Frederick's Crusade and its achievements have been downplayed, and the extent of his impact on the movement has been under-appreciated. Frederick's career, meanwhile, also posed questions about the definition of Crusades and the papacy's role therein.

Frederick II of Hohenstaufen was the grandson of Frederick Barbarossa, and the heir to a Crusading tradition. With the near-fatal blow that the Byzantine Empire had suffered in 1204, and although Capetian France was on the ascent, there was no secular ruler who could so-credibly claim to have inherited the authority of the Caesars, and the leadership of Christendom. The papacy, however, made claims of its own to universal supremacy, increasingly involving itself in the temporal sphere. Conflict between Rome and the Holy Roman Empire had caused recurring strife within Europe, and had previously hampered the organization of Crusades. Frederick II was also heir to this unresolved power-struggle, played out primarily in Italy.
In the years when Frederick was coming of age, though the Crusading movement retained popularity, it was becoming tarnished. The cause had met with such setbacks that troubadours expressed disgust with the quarrelling rulers of Christendom, and even with God, for allowing the failures. The Third Crusade had concluded disappointingly, and Richard I's subsequent experience indicated that the 'peace of God' was a defunct notion. Afterwards Pope Innocent III had inaugurated an era of crusades against Christians, preaching against Markward of Anweiler. It therefore cannot be said that Crusading, because of Frederick, was grafted to the political situation in Italy although as a result of the hostility between the papacy and Frederick the phenomenon would resurface. The politicisation may be traced to Innocent III, who enshrined the papacy's claim to temporal authority in central Italy and to suzerainty over the Kingdom of Sicily. Innocent established the precedent for the later pontiffs who would assert these territorial claims, and declare crusades against Frederick and his heirs.

In 1202-04, the Fourth Crusade was diverted by Venetians interests towards the attacks on Zara and Byzantium. Innocent's initial displeasure was mollified by the installation of Latin clergy in Constantinople, and by a share of the spoils. Five years later he sent Crusaders against the Albigensians. Despite his avowed desire to see Jerusalem recovered, Innocent's projects hardly advanced that aim, instead seeing Christian regions ravaged. It is hard to imagine much real idealism motivating the perpetrators of these atrocities; certainly those on the receiving end doubted it. Many besides felt that an authentic Crusade should focus on Jerusalem. Tellingly, the Templars and Hospitallers avoided active participation in the controversial crusades. The transformation, even so, had taken place from crux transmarine to crux cismarina. Even before Frederick's era, the Crusades had rebounded into Christendom.

The Fifth Crusade was also Innocent III's conception, though he died before its commencement. It was an opportunity to put Crusading back on course. However, this campaign too was misdirected, focussing, ultimately, on the conquest of Egypt. The Crusaders beset Damietta and in November 1219, after a costly siege, captured it. To the consternation of some, Pelagius refused peace proposals from Sultan al-Kamil, who offered to return all of Palestine apart from two castles beyond the Jordan. Pelagius delayed in Damietta throughout 1220, waiting for Frederick. (He also hoped for deliverance from the mythical Prester John- garbled reports of Chingis Khan's advance having fuelled false expectations). The delay was costly, and in the meantime Frankish Palestine also lay vulnerable. Even so the Muslims feared the loss of Egypt as a result of the Crusaders' presence, and felt beset on two fronts, with the Mongols encroaching into Mesopotamia. Ibn al-Athir may have been melodramatic to predict doom- Egypt had lost only one city- but if he truly reflected Muslim anxiety at that juncture then Frederick's arrival might indeed have precipitated the collapse of Ayyubid power. Frederick's earliest impact on the Crusades, then, was as the leader who never materialised.

The Crusaders' delay allowed the Ayyubids to regroup. Frederick did send an advance force under the pugnacious Ludwig of Bavaria, who arrived in June 1221. The decision was made to advance south, despite the approaching inundation. Near Mansourah, the expedition was bottlenecked beside the rising Nile, and trapped 'like fish in a net' after the Egyptians opened a channel behind them. Surrounded by water and enemies, the Christians had to exchanged Damietta for their lives. Their comrades in Damietta complied with the terms, despite the arrival of fresh imperial forces under Henry of Malta; thus the venture failed. Allegedly Frederick had forbidden negotiation with the Muslims until his arrival, a factor in Pelagius's seeming stubbornness. Whether or not Frederick was indirectly responsible for this debacle, he evidently bore some of the recriminations. (Honorius III was also criticized for supporting Pelagius's stance.)

Frederick had been detained first by affairs in Germany then by a rebellion in the Sicilian mountains. That the rebels were irredentist Muslims did something to excuse his failure to embark. Frederick was evidently still seen as the leading hope for Crusading. It has been said that he was an unusual Crusader, being the product of his mother's cosmopolitan inheritance, where Byzantine and Islamic cultural influences persisted. This may be so but Bohemond and Tancred had hailed from similar regions, and this had hardly compromised their credentials. Frederick clearly felt no animus against the Muslim, per-se but rather considered them people he could treat with. Although he had been ruthless in putting down the Sicilian Muslim revolt, and forced many to relocate to Apulia, he allowed them to practice their faith there, isolated in Lucera, where they settled to become dependable subjects. Frederick placed such trust in them that when he finally did embark on Crusade he took Muslim bodyguards- a departure from the norm, although some of Sicily's Norman rulers had also enlisted 'Saracen' guards.
In March 1223, leaders of the Latin East, including John of Brienne and representatives of the Military Orders, met Frederick at Ferentino. They decided to postpone the planned Crusade for two years. The delegates also decided to offer Frederick the hand of John's daughter Yolande of Jerusalem. Honorius supported this arrangement, hoping it might augment Frederick's Crusading interests. The marriage took place in 1225, linking the Emperor to the dynasty that had dominated the Crusades. Frederick at once asserted his authority over the Latin East, marginalizing his father-in-law. Frederick continued to delay his departure until the birth of an heir, who would cement his position. Conrad's birth (though overshadowed by Yolande's death) gave Frederick a personal incentive to recover Jerusalem, his son's birthright. There were grounds to hope, therefore, that Frederick would put the Crusade back on track, an intention he affirmed at San Germano. Rome probably had a vested interest in making Frederick commit to the new Crusade that went beyond concern for his soul and the recovery of Christ's patrimony.

The curia was keen to have Frederick absent on a long campaign as his presence in Italy seemed to threaten Rome's own position and thwarted its ambition to dominate the peninsula. Rome's underlying agenda was to prise the kingdom of Sicily from the northern Empire. Perhaps, though, some in the curia began to fear that this might become harder should Frederick succeed and win prestige as a Crusader. Thus forces within the curia may have plotted subversive action even as Frederick built his fleet.
News of Frederick's preparations, meanwhile, motivated al-Kamil of Egypt to send his envoy to Palermo. Fakhr al-Din returned reports of a cultivated European ruler who esteemed Islamic culture. The envoy and the emperor became friends and a correspondence commenced also between Frederick and al-Kamil . Perhaps at this time the notion dawned in the East that here was a Westerner whom Egypt could do business with, and perhaps use. Even before Frederick embarked, the tacit understanding was reached that al-Kamil would cede Jerusalem in exchange for assistance against his rebellious brother, al-Muazzam of Damascus. Although Franco-Arab alliances were nothing new, this level of collusion between a Sultan and a Crusade was unprecedented. For Frederick, though, it was all a means of achieving Jerusalem. If the Holy Places could be regained with minimal bloodshed then all the better. Augustinian doctrine, after all, supposed war to be a last resort. True, some Christian minds had become so warped that Holy warfare seemed an end in itself, surpassing the stated objectives of the given campaign. However even St Bernard had conceded that the Infidel was only to be slain when there was no other option. He would have been obliged to condone Frederick's expediency.

Frederick embarked in 1227 but was forced back by illness. Pope Gregory IX (a Conti like Innocent III and likewise a rigid papal supremacist) excommunicated Frederick, ostensibly for this latest in a series of delays. Actually Gregory was using this to justify a wider campaign against the imperial position. In 1288, unreconciled, Frederick left for the Holy Land. Thousands of others accompanied him, indicating that society did not necessarily deem a legitimate Crusade dependent on papal endorsement. The movement had a life of its own. This revelation may be considered part of Frederick's legacy, and surely embarrassed the papacy. It marked a distinct divergence between papal crusading, premised on the offer of indulgences, and popular Crusading, driven by lay devotion and the pilgrimage impulse. (The centrality of the papacy to Crusading in general may have been exaggerated by curia-centric historians. ) But for past Crusaders to have pre-empted Papal invitation was one thing, to Crusade under excommunication was another. Frederick's decision to proceed thus amounted to taking up the gauntlet in a battle of wills with Rome. It also meant that for the first time the curia would find itself actively out to undermine the efforts of Crusaders striving to recover Jerusalem. It had little choice, if it was not to rethink its doctrines, for the Crusade, under Frederick, seemed now a movement to invalidate rather than consolidate papal supremacy.

Frederick's initial impact in the Levant was inauspicious. His attempt to intimidate John of Beirut at a banquet at Limmasol backfired when John stood firm for the prerogatives of the Latin barons, despite the entry into the hall of imperial troops. This set the tone for later confrontations. Problems were caused less by Frederick's excommunication than by his presumption that he would receive automatic submission. Crossing to Tyre, Frederick received a warm reception from the Christian inhabitants. Templars and Hospitallers kissed his knees. Most were less concerned about his spiritual condition than they were grateful for the military support he brought. Frederick sent Rome notification of his arrival. The Eastern Latins hoped this would dispose Gregory to absolve Frederick, so that the Crusade could proceed conventionally. However Frederick had sent among the messengers Rainald of Spoleto, lord of lands claimed by the papacy, whom Gregory refused to see. The embassy achieved the opposite of the desired effect.

Refortification commenced at Caesarea and Joppa. Then, supplies having arrived, the Crusaders marched out to reclaim Jerusalem. Relations between Frederick and the Eastern Latins deteriorated when his unforgiven status became widely known. Moreover his autocratic style ruffled feathers, in a region used to a more corporate system of government. He became an enemy especially of the Templars, then under Peter de Montaigu. Matthew Paris recorded that they later sought Frederick's death, and sent a message to the Sultan revealing that Frederick would visit the River Jordan undefended where the Muslims could ambush him. The Sultan, in disgust, supposedly forwarded the Templars' message on to Frederick, complete with incriminating seal. Though it seems unlikely the Templars would actually have been so naive as to solicit the Sultan against Frederick this way, a Muslim source does attributes Frederick's reluctance to stay long in Jerusalem to fear of the Templars; clearly they became resolute opponents of his. He in turn disseminated propaganda against them, saying that they were secretly working against the Christian cause, because if the Crusades succeeded their calling would be redundant. This slur gained some currency, and would be repeated, supposedly, by Robert of Artois, during the Seventh Crusade, when attempting to goad the Templars into action at Mansourah. The persisting slur against the Templars was a less fortunate bequest of Frederick to the Crusading Movement. Perhaps it was remembered at the time of their suppression. After all, according to Frederick (if Paris accurately reflects imperial allegations), the Templars had stooped to betraying the pilgrims they once defended. Frederick went to the lengths of besieging them in Atlit. By this time he had already crowned himself in the Holy Sepulchre, after which the Patriarch Gerold, from Acre, had placed Jerusalem under interdict. It was all, indeed, 'hardly edifying'.

Frederick had entered Jerusalem supported by Teutonic Knights, German pilgrims and Sicilian and English bishops. Evidently the Church was not united in its opposition to him. Frederick, even knowing that the Pope had worked against his efforts, made a conciliatory speech during his coronation. He might have hoped that the Church would respond by lifting his excommunication and ending the farce. When the Church did the opposite, Frederick was furious. News of Gerold's interdict was delivered by the Archbishop of Caesarea, and it immediately ended the tenuous co-operation Frederick had established with the Military Orders. Gerold's action also made it clear that the Church presumed the authority to put any earthly location beyond the grace of God. Popes and Patriarchs could desanctify even Jerusalem. The interdict exposed the Church's view of it as just another place subject to ecclesiastical sanctions.

Jerusalem's sacred sites had been restored to Christian custody, as Frederick put it, almost miraculously. No one seemed more offended than the high clergy. The Church had attributed the failure of previous Crusades since the mid twelfth century to God's punishment for the sins of Christians (peccatis ecigentius). An impact of Frederick's success was to call this explanation into question, given that the Church was already portraying him as reprobate. Frederick's victory therefore caused problems to clerical commentators, challenging the moral rationale of Holy War. It certainly undermined the Church's control over Crusading as a penitential exercise, as the participants of Frederick's Crusade evidently felt that it had value even without the indulgences being on offer. This discrepancy of interpretation was something Frederick helped to expose.

One response to this problem for the papal faction was to pick holes in Frederick's achievement. It seemed Jerusalem could not be fortified, in accordance with the treaty, and the sacred precincts of the Temple, which Frederick toured in the company of his Muslim host, were to remain Islamic. Gerold thundered against Frederick, likening him to the Antichrist. He called Frederick's actions deplorable and detrimental to the cause of the Christian faith. He catalogued Frederick's misdeeds including coming excommunicated and mistreating the local nobility. Unilaterally, and after 'long and mysterious conferences' with the Muslims, Frederick had announced his truce, and had gone to Jerusalem with only the Sultan's word that it was to be surrendered. He had crowned himself in the Holy Sepulchre, although the Saracens still held the Temple, and although they 'proclaimed publicly the Law of Mohammed- to the great confusion and chagrin of the pilgrims.' Frederick had skulked out of Jerusalem despite the promise of the Military Orders that they would help him refortify it. Frederick was content with Jerusalem's nominal surrender, and had no care to make it secure. The main, underlying criticism was that Frederick trusted the Muslims. Few of the Patriarch's charges withstood scrutiny, for Islamic worship had continued previously in the Kingdom of Jerusalem without confounding the Christians, as the ever-diplomatic Hermann von Salza mentioned in a letter to a friendlier cardinal in Rome. Gerold himself was responsible for wrecking Frederick's rapprochement with the Military Orders. If Gerold's biggest complaint was that Frederick had pulled off only a partial success, than under the circumstances that was fatuous. Gerold represented an institution with ulterior motives for seeking to discredit Frederick; indeed papal mercenaries were besetting Frederick's lands even as he entered Jerusalem. So much, then, for the Peace of God.

The Sixth Crusade was successful, compromises and clerical maligning notwithstanding. Church-backed Crusades had poured out blood to no avail, whereas Frederick had gained all he had with barely a skirmish. He was well placed to claim divine vindication, and was not slow to. Jerusalem, Bethlehem and Galilee again lay within a recovering Christian enclave. It was a great diplomatic tour-de-force on Frederick's part that he had persuaded al-Kamil to make these concessions, especially given how little he offered in return. Moreover Frederick's policy of supporting Egypt against Damascus might have preserved these gains. It was only when certain Frankish factions (including the Templars under Armand de Perigord) sought to reverse this alignment that Jerusalem was again lost - ravaged by Khoresmians summoned by a panicked Cairo. The new Syrian alliance was of little worth and crumbled after la Forbie. This new disaster was less the result of Frederick's policy than of its abandonment.

Frederick II with a falcon. Frederick wrote a book on falcory

When discussing Frederick and the Crusades, it becomes superfluous to speak of irony. Other Crusaders had won admiration from the Saracens as worthy opponents, but none left such a good impression with the Muslims, or at least with Egypt's elite. Ibn Wasil recorded that Frederick was a ruler 'distinguished and gifted, a student of philosophy, logic and medicine and a friend of Muslims.' This legacy of admiration was confirmed by Jean de Joinville. In 1250, when Joinville was captured aboard a vessel on the Nile, the Saracen admiral asked if he happened to be related to Frederick of Germany. Joinville replied that he thought his mother was the emperor's first cousin '…whereupon the admiral remarked that he loved me all the more'.
Frederick's struggle with Rome had overshadowed the Sixth Crusade. Frederick himself was not entirely responsible for this, for while either side showed intransigence, Frederick was generally the more conciliatory. Rome could have absolved Frederick when he embarked for the east, when he arrived in Tyre and when he entered Jerusalem. Gregory personally might have had to swallow pride to do so but in reality the Church would have lost little face. It would have been seen to be acting magnanimously, for the general good of Christendom and the participants of the Crusade, and, moreover, according with divine will. It could also then have shared in the glory of the recovery of Jerusalem. Instead of attempting to sabotage that achievement the Church could have helped to consolidate it. It is unfortunate that the Curia was so ungracious. The papacy created a crisis for itself, and sacrificed its own credibility as a source of spiritual leadership. Its later crusades against Frederick and his heirs would prove yet costlier in this respect.

John of Brienne had been leading papal armies attacking Apulia. Frederick landed in Brindisi in June 1229, and by October had chased his erstwhile father-in-law back into papal territory. Rather than pushing his advantage, however, Frederick halted and sought peace. Hermann von Salza mediated, persuading a reluctant Gregory to absolve Frederick on 1 September 1230. Frederick subsequently helped the Teutonic Knights establish themselves as the vanguard of the ongoing Baltic Crusade. The birth of the Order's state in Prussia was to some extent another legacy of his. Hermann von Salza, meanwhile, continued endeavouring to preserve harmony between his two overlords. Relations between Frederick (who was engaged in war with the Lombard league) and Gregory remained strained and Hermann died on the same day that Frederick was again excommunicated (20 March 1239). By February 1240, Frederick was poised to enter Rome itself, and the Pope called a crusade against him. Afterwards, at the Council of Lyons, Innocent IV declared Frederick deposed, and prioritised an anti-Hohenstaufen crusade over Louis IX's projected Eastern expedition. Papal letters flew about detailing Frederick's 'manifold villainies' Innocent's propagandists also accused Frederick of impeding aid to Jerusalem, while Frederick countered that only papal hostility prevented him from succouring the Holy Land. Papal obstinacy over Frederick also hampered Louis's preparations.
Matthew Paris was critical of the anti-Hohenstaufen crusades, and of Innocent's demands for English funds and troops. Paris recorded how English Crusaders swore an oath to proceed to the Holy Land, and not to be diverted by Rome to fight in Greece or Italy, indicating grass-roots scepticism concerning papal policy. Another critic was the Venetian Marino Sanudo, who urged an end to the wars in Italy, seeing them as a major reason for eastern losses. Housley has argued that the Italian crusades were not viewed by most contemporaries as perversions of the Crusade ideal, or devaluing to indulgences. However he conceded that the popes who concentrated on these wars were criticized from many quarters. The view that these crusades were scandalous and detrimental to the cause of the Latin East can withstand such attempts at revisionism. Only those with political interests in the Guelf cause could have convinced themselves that these civil wars were remotely holy. That Rome was willing to resort to bribery, and to restrain the Inquisition in regions where it might jeopardise anti-Hohenstaufen alliances, moreover, perhaps shows willingness to compromise principles, and the shifting nature of alliances in these conflicts made it difficult to associate them with higher ideals.

Rome's exploitation of Crusading to serve its worldly interests was resisted by purist Crusaders. Richard of Cornwall's force in 1239 refused to have their vow to assist the Holy Land commuted, and would not be steered aside. Frederick indeed, backed Richard of Cornwall's Crusade of 1240 and might have supported the Seventh Crusade but for Innocent's hostility. Frederick was not without clerical supporters, either. In 1240, for example, the dean of Passau publicly preached the cross against the papal legate Adam von Bahem, who had been sent to discipline the pro-imperial clerics. Thus the 'anti-crusade' was born. It was not the last time Christians would proclaim holy war against each other. It seems a natural reaction, however; it would have been unreasonable for Frederick's supporters (themselves potential Crusaders) to accept Rome's invectives. Frederick, after all, could and did argue that as the restorer of Jerusalem, he and not the Pope had been the true instrument of God's will. The anti-Hohenstaufen crusade was one in a succession of political/territorial conflicts involving the papacy, which ultimately brought Crusading into disrepute. It is difficult, however, to see how Frederick could have avoided the conflict without allowing Rome to establish theocratic mastery over Europe. (Gregory had claimed in 1236 that the whole earth was subject to the judgement of the Apostolic See). Frederick died in 1250 passing into legend. As it was, the Church triumphed over his heirs, though in the process it bound itself to Capetian tyrants and ended up with similar problems as it had before.

Frederick's status as a Crusader has been underestimated. In a short time he did more for Latin Palestine than any Christian leader since Richard. Surpassing Richard, Frederick recovered Jerusalem, and did so peacefully, while the violent efforts of previous Crusaders had tended if anything to do more harm than good. Frederick's impact on the Crusades in the Holy Land was on balance positive, and may have been more so but for the Church's uncharitable behaviour. Later Frederick became the subject of papal crusades. The impact of these wars was universally negative, hampering support for Jerusalem, and causing widespread strife and division at a time when European unity was vital in order to maintain Crusading efforts and to confront the looming threat from the Mongols.

The premise of a Crusade was of a Holy War, and, from a curial standpoint, of papal authority on God's behalf to grant indulgences to the participants. Success or failure, however, depended on divine favour. All the later Crusades that embarked with papal blessing failed to achieve their objectives. Frederick's Crusade, which succeeded in spite of a papal curse, did achieve its material goals. This undermined the theology of Crusading as predicated by the clergy. Frederick's success also brought into focus that aspect of the Crusading movement that while still religious was more than a vehicle for upholding papal authority. Instead it subverted papal pretension. When it came to warfare in Europe (which Rome was prepared to wage at Jerusalem's expense) Frederick had no little justice on his side, and little choice but to resist an increasingly absolutist enemy.
There is a more positive aspect to Frederick's Crusading legacy. His 1229 arrangement with al-Kamil over Jerusalem set an example of compromise. It was a victory of diplomacy over force, and of humanity over bigotry. As David Abulafia has suggested, it points to the possibility of mutual tolerance between religious groups and coexistence as a way forward for the Holy Land. Although the treaty was born largely from political expediency, from a progressive point of view it was the finest moment in the history of the Crusades.

Bibliography
Primary Sources
Bernard of Clairvaux. 'In Praise of the New Knighthood':
Greenia, C. (trans.), Werblowsky, R.J.Z. (intro.), in Works of St Bernard of Clairvaux, vol. VII, treatises, 3.

Ibn al-Athir, Ibn Wasil &c.:
Gabrielli, F. (trans.) Arab Historians of the Crusades (London 1969).

Jean de Joinville, 'Vie de Saint Louis':
Shaw, M.R.B. (trans.), Joinville and Villehardoun, Chronicles of the Crusades (London 1963).

'L'Estoire d'Eacles Empereur':
Recueil des Hostoriens des Croisades. Historiens Oxidentaux, vol. 2, (Paris, 1844-59) pp. 436-42.

Matthew Paris, 'Chronica Majora':
Vaughan, R., (trans.) The Illustrated Chronicles of Matthew Paris: Observations of Thirteenth Century Life (Stroud, 1993).

Oliver of Paderborn, Patriarch Gerold, Frederick II, Roger of Wendover etc. :
Peters, E. (ed.) Gavin, G.J. (trans.) Christian Society and the Crusades 1198-1229: Sources in Translation including The Capture of Damietta by Oliver of Paderborn (Pennsylvania, 1948).

Philip de Novarre:
Philip de Novare: Les Gestes des Ciprois, No. 135-37, ed. Gaston Reynaud, (Geneva: Jules-Guillaumefick, 1887), 48-50, translated by James Brundage, The Crusades: A Documentary History, (Milwaukee, 1962), pp. 231-32

Secondary Works
Abulafia, D., Frederick II, A Medieval Emperor (London 2002).
_____., The Two Italies (Cambridge, 1977).
Aziz, M.A., 'La Croisade de l'Empereur Frédéric II et l'Orient Latin', Autour de la Première Croisade; Actes du Colloque de la Society for the Study of the Crusades in the Latin East (Clermont-Ferrand, 22-25 juin 1995). ed. M. Balard (Paris, 1996).
Barber, M., The New Knighthood (Cambridge, 1994).
Bartlett, R., The Making of Europe (London, 1993).
Billings, M., The Crusades (Stroud, 2000).
Forey, A., The Military Orders from the Twelfth to the Early Fourteenth Centuries (Basingstoke, 1992).
Hilenbrand, C., The Crusades: Islamic Perspectives (Edinburgh, 1999).
Jotischky, A., Crusading and the Crusader States (Harlow, 2004).
Lock, P., The Routledge Companion to the Crusades (London, 2006).
Kantorwicz, E. Frederick the Second (New York, 1931).
Maalouf, A., The Crusades through Arab Eyes (Paris, 1983).
Masson, G. Frederick II of Hohenstaufen, a Life (London, 1957).
Mayer, H.E., The Crusades, 2nd edition, trans. J. Gillingham (Oxford, 1988).
Nicholson, H., , The Knights Templar, a New History (Stroud, 2001).
Omran, M.S., 'Truces between Moslems and Crusaders (1174-1217 A.D.)' Autour de la Première Croisade, ed. M. Balard (Paris, 1996) p. 423-441.
Phillips, J., The Fourth Crusade ( London, 2005).
Powell, J.M., Anatomy of a Crusade 1213-1221. (Pennsylvania 1986).
Read, P.P., The Templars (London, 1999).
Riley-Smith, J.S.C., ed., The Oxford Illustrated History of the Crusades (Oxford, 1995).
_____, What Were the Crusades, (Basingstoke 2002)
Runciman, S., A History of the Crusades: the Kingdom of Acre and the Later Crusades (Cambridge, 1955).
Seward, D., The Monks of War (London, 1972).
Smith, C., Crusading in the Age of Joinville (Aldershot, 2006).
Tyerman, C., The Invention of the Crusades (London, 1998).
_____, God's War (London, 2006).
Van Cleeve, T.C., The Emperor Frederick II: Immutator Mundi (Oxford, 1972).

Journal Articles:
Throop, P.A., 'Criticism of Papal Crusade Policy in Old French and Provençal', Spectrum, vol 13, no. 4 (1938).

Weiler, B., 'Image and Reality in Richard of Cornwall's German Career', The English Historical Review, Nov 1998, pp.1111-1142.

Powell, J.M., 'Frederick II and the Church in the Kingdom of Sicily 1220-1224' Church History (1961) pp. 28-34.