The Sixth Crusade (1228–1229), also known as the Crusade of Frederick II, was a military expedition to recapture Jerusalem and the rest of the Holy Land. It began seven years after the success of the Fifth Crusade and involved very little actual fighting. The diplomatic maneuvering of the Holy Roman emperor and king of Sicily, Frederick II, resulted in the Kingdom of Jerusalem regaining some control over Jerusalem for much of the ensuing fifteen years as well as over other areas of the Holy Land. Frederick II's negotiations and power-sharing agreement and negotiation with envoys from al-Malik Al-Kamil of Egypt, which led to a shared Christian-Muslim governance situation in Jerusalem, made this Crusade different from the others. Frederick II carried out his maneuvers in 1228 while under excommunication from the Church by Pope Gregory IX.
Western Europe after the Fifth Crusade
The Fifth Crusade ended in 1221, having failed to gain any more influence in the Near East. Frederick II, Holy Roman emperor, never joined the campaign, despite his vow to do so. The forces he sent to Egypt arrived too late to make a difference in the debacle, partially due to the lack of effective leadership. They would have to wait for many more years for Frederick's actions. When Pope Innocent III died in 1216, his successor Honorius III did not immediately hold Frederick to his vow, but reminded him that the Christian world had waited for his action. However Gregory IX, the successor to Honorius, who became pope in March 1227, took a more hardline stance against the emperor. In Syria and Egypt, the Ayyubids were engaged in civil strife, in which the sultan al-Kamil fought against many of his brothers and other relatives. The sultan had yet to withdraw his offer of territory in exchange for peace that had been made during the Fifth Crusade, and Frederick would eventually accept this deal.
Frederick II and the Papacy
The failure of the Fifth Crusade was a devastating blow to Christendom. Of all the European sovereigns, only Emperor Frederick II was in a position to regain Jerusalem after the loss. Frederick was, like many of the 13th-century rulers, a serial crucesignatus. When he was formally crowned as King of Germany at Aachen on 15 July 1215, he astonished the crowd by taking the cross and calling upon the nobles present to do the same. Twenty years separated the crusader vows of Emperor Henry VI and his son Frederick and it is unclear whether the father's German Crusade of 1197 impacted the son's objectives for the Fifth Crusade.
The emperor again took the vow when he was re-crowned in Rome by the pope on 22 November 1220. At the same time, Frederick's oldest son, Henry, took the title of king of the Romans, and Frederick's wife, Constance of Aragon, was crowned empress. A year later, Honorius III reminded Frederick that he had not fulfilled his vow, and in December 1221, sent Nicola de Chiaromonte, cardinal-bishop of Tusculum, to confer with Frederick. They returned to Veroli in April 1222 to confer with the pontiff. A strategy meeting for the next Crusade did not happen until March 1223 at Ferentino and included the pope and emperor, plus John of Brienne, Latin patriarch Ralph of Mérencourt, the masters of the military orders, and many others. Frederick again vowed to go on Crusade in addition to signing an agreement with the errant Thomas of Celano, negotiated by Thomas of Aquino. But neither this nor the one signed two years later at San Germano assured Frederick's departure.
A new date was set for the expedition of 24 June 1225. At the same time, Frederick, widowed since June 1222, planned a strategic wedding. After the retreat of the Crusaders from Egypt in 1221, John of Brienne returned to Acre. He hoped to find a suitable husband for his daughter Isabella II of Jerusalem, then just 9 years of age. Leaving Odo of Montbéliard as bailli of the kingdom, he travelled to Italy, accompanied by Patriarch Ralph and Hospitaller master Guérin de Montaigu. In Apulia, he met with Frederick II and arranged for the marriage of Isabella II to the emperor. The pope gave his blessing, and it was John's understanding that he remain regent until 1226. When John left Italy, marrying Berengaria of León in 1224, he entrusted Hermann of Salza to conclude the arrangements for the wedding of his daughter.
Once again, preachers were sent throughout Europe to gain support for a new crusade, this time to be led by Frederick. Despite readying transport ships, the situation did not look good to meet the target date. Hermann of Salza and Ralph of Mérencourt were sent to the pope to apprise him of the situation. That would be one of the patriarch's last official acts, as he died in late 1224, succeeded by the bishop of Valence, Gérold of Lausanne. Honorius III sent cardinal bishop Conrad of Porto as papal legate to Germany, urging the clergy there to continue to pursue the crusade. The pope also urged Louis VIII of France to join Frederick, and to resolve his quarrel with Raymond VII of Toulouse. None of these efforts were fruitful and all were convinced that the timetable set at Ferentino was unachievable. The pope while at Rieti agreed to a delay on 18 July 1225, just days before the deadline and ten years after Frederick had originally committed to a crusade.
Agreement of San Germano
The Agreement of San Germano of 25 July 1225, signed at present day Cassino, was between Frederick II and Honorius III. A Dominican named Guala de Roniis was responsible for the negotiations. Frederick promised to depart on the Crusade by 15 August 1227 and remain for two years. During this period, he was to maintain 1000 knights in Syria, provide transport for additional forces, and provide Rome with 100,000 ounces in gold in the care of Hermann of Salza, John of Brienne and the patriarch. These funds would be returned to the emperor once he arrived at Acre. If, for any reason (including his death), he did not arrive, the money would be employed for the needs of the Holy Land. He also promised that if he went on Crusade that he would lead. After the agreement was signed, Guala became Bishop of Brescia. Based on the terms of the agreement, Frederick's forces ceased to occupy portions of the pontifical states. Moreover, all papal possessions in the Kingdom of Sicily were to be restored to the pope.
Frederick attested to the terms at the high altar with his hand on the Gospels. Apostolic legate Rainald of Urslingen, the duke of Spoleto, swore "on the soul of the emperor" that the agreement would be upheld under the pain of excommunication. In a letter to the pope, Frederick reiterated the terms and accepted the ban in the event the Crusade did not happen. He had committed himself beyond all retreat.
Situation in Italy
After agreeing with Honorius to launch a Crusade before 1228, Frederick summoned an imperial Diet at Cremona, the main pro-imperial city in Lombardy. The main arguments for holding the Diet would be to continue the struggle against heresy, to organize the crusade, and to restore the imperial power in northern Italy, long usurped by the numerous communes located there. Those assembled responded with the reformation of the Lombard League, which had already defeated the emperor Frederick I in the 12th century, and again Milan was chosen as the league's leader. The Diet was cancelled as well as the Truce of Constance. The situation was stabilized only through a compromise reached by Honorius between Frederick and the league. During his sojourn in northern Italy, Frederick also invested the Teutonic Knights with the territories in what would become East Prussia, starting what was later called the Northern Crusades.
King of Jerusalem
Frederick II desired to go to the Holy Land as king of Jerusalem. He married John of Brienne's daughter Isabella II by proxy in August 1225 at Acre, presided over by Giacomo, the bishop of Patti. In accordance with her father's wishes, she was crowned queen of Jerusalem a few days later at Tyre. Frederick sent fourteen galleys for her, under the command of admiral Henry of Malta, pardoned since his role at the disaster at Mansurah during the Fifth Crusade. They were formally married at Brindisi on 9 November 1227.
John and Frederick's relationship became frayed, as Frederick claimed the kingship of Jerusalem. John had allegedly been given assurances that he would be king of Jerusalem for the rest of his life. According to one version, John got into a disagreement with his new son-in-law because Frederick seduced a niece of Isabella who was her lady-in-waiting. In the other version of the chronicle, John often chastised his son-in-law, concluding that John wanted to seize Sicily for his nephew Walter IV of Brienne. Frederick declared that John had lost his claim to the kingdom when Isabella married him. He proclaimed himself king of Jerusalem for the first time in December 1225, taking the crown at a special ceremony at Foggia.
John of Brienne left for Rome, where Honorius sympathized with him, and ignored Frederick's claims. Balian of Sidon, Simon of Maugastel, the archbishop of Tyre, and the other Jerusalemite lords who had escorted Isabella to Brindisi acknowledged Frederick as their lawful king. Notably, these did not include the Ibelins. Nevertheless, the law––the Assizes of Jerusalem––required that the monarch be a resident of the kingdom. Frederick's first royal decree was to bestow new privileges upon Hermann of Salza and the Teutonic Knights, placing them on equal footing as the Templars and Hospitallers. Thomas of Aquino, the emperor's long-time advisor, replaced Odo of Montbéliard as bailli of the kingdom.
Financing the Crusade
In November 1222, John of Brienne arrived at Brindisi, the first king of Jerusalem to visit Europe, with multiple objectives. The treasury of the kingdom was depleted and additional funds were badly needed. He also wanted to ensure that future crusades were not hampered by the divided leadership shown in Egypt, and that the kingdom would lead such efforts. John's pleas for support at the courts of England and Spain were for naught, and the pledge he received from Philip II of France on his death-bed was from an account already allocated to the Holy Land. Henry III of England did eventually implement a levy but it is not clear that much was made from the voluntary contributions.
The conciliar decree Ad Liberandam published at the Fourth Lateran Council in 1215 formed a system of public financing of Crusades. The disbursements from the papal camera formed essential aid to the crusade movement, although the monies collected by individual crucesignati remained important. While some of these funds went directly to local Crusaders, by 1220, Innocent III had consolidated distribution. Frederick did not benefit from this, and from 1221 to 1228 there was limited ecclesiastical impost directed toward his planned Crusade. The funds for this imperial Sixth Crusade would have to be raised by the emperor. The gold sequestered after San Germano was quickly spent due to the delay of the crusade, and Frederick implemented a levy on Sicily beginning in 1228. He also gained financial support from Cyprus and as his new role as king of Jerusalem, but the lack of funds contributed to the small size of the Crusader army.
Ayyubids after 1221
The defeat of the Crusaders in the Fifth Crusade was a joint effort of the brothers al-Kamil, al-Mu'azzam and al-Ashraf. After 1221, al-Mu'azzam returned to Damascus, suspicious of his brothers and their motivations. In June 1222, he conducted an expedition against Guy I Embriaco to enforce the truce, and unsuccessfully attacked his cousin al-Nasir Kilij Arslan, emir of Hama, and later occupying Ma'arrat al-Numan and Salamiyah. Al-Mu'azzam was forced to halt his siege of Hama and to surrender his other conquests by order of al-Kamil. He then formed an alliance with Gökböri, a former general of Saladin's, possibly at the request of the sultan al-Nasir, against his brother al-Ashraf.
Another brother, al-Muzaffar Ghazi, had been installed at Mayyafariqin and Akhlat, losing Akhlat to al-Ashraf after revolting against him. Ghazi joined the rebellion of al-Mu'azzam's, which was quickly suppressed by al-Ashraf and the Alleppine forces. Again attacking at Homs, al-Mu'azzam was restrained by threats from al-Kamil. Now opposing both of his well-positioned brothers, al-Mu'azzam reached out to disaffected members of the sultan's Egyptian forces, challenging the sultan to come to Syria if he dared. Against al-Ashraf, he enlisted the aid of the Khwarazmians under the shah Jalal al-Din Mangburni to attack Diyar Bakr.