[7] 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 Raoul of Mérencourt, the masters of the military orders, and many others.

Leaving Odo of Montbéliard as bailli of the kingdom, he travelled to Italy, accompanied by patriarch Raoul of Mérencourt and Hospitaller master Guérin de Montaigu.

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.

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.

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.

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.

At this point, al-Kamil began exploring peace with the West, dispatching the emir Fakhr ad-Din ibn as-Shaikh to meet Frederick II (see below).

[30] The initial phase of the Crusade was a complex endeavour involving multiple deployments, negotiations with the Ayyubids, a delay of the departure of Frederick due to illness, a subsequent excommunication, and, finally, arrival of the emperor at Acre.

The sultan sent the emir Fakhr ad-Din ibn as-Shaikh to Frederick asking him to come to Acre for discussions, offering return of much of the Holy Land to Christian control in exchange for military support against his brother al-Mu'azzam at Damascus.

Fakhr ad-Din reportedly was somewhat amazed when he reached Palermo and discovered that Frederick spoke Arabic, had admiration for Muslim society and contempt for Rome.

[39] Frederick responded by sending his bailli and trusted advisor Thomas of Aquino and Berardus de Castacca, archbishop of Palermo, to meet with al-Kamil.

The bishop is reported to have continued on the Damascus to negotiate with al-Mu'azzam who, rejecting the overture, attempted to make peace with the younger Ayyubid brother al-Ashraf.

In his circular letter announcing the excommunication, Frederick was branded a wanton violator of his sacred oath taken many times, at Aachen, Veroli, Ferentino, and San Germano, and was held responsible for the deaths of Crusaders at Brindisi.

This revelation changed the balance of power, and Frederick dispatched Richard Filangieri, marshal of the Kingdom of Sicily, to Syria with 500 knights to augment to force already there as he prepared for a departure in the spring of 1228.

The fleet was under the command of admiral Henry of Malta, and clergymen Berardus de Castacca, Nicolò dei Maltraversi, Marino Filangieri, and Giacomo of Patti, now archbishop of Capua, accompanied him.

[49] Guérin de Montaigu, master of the Hospitallers who had helped convince the pope to break the truce with the Muslims, refused to accompany Frederick as an excommunicate.

[49] The Kingdom of Cyprus had been an imperial fief since the emperor Henry VI, Frederick's father, had accepted the homage of Aimery of Lusignan and made him king on the eve of the German Crusade in 1196.

[54] Frederick II arrived in Acre on 7 September 1228 and was received warmly by the Templars, Hospitallers and clergy, but denied the kiss of peace due to his excommunication.

He yielded to pressure and made overtures to the pope, sending Henry of Malta and archbishop Marino Filangieri to announce his arrival in Syria and to request absolution.

But Gregory IX had already made up his mind, sending word to the Latin patriarch and masters of the military orders that the emperor's ban still held, despite his arrival.

[55] When Frederick and his companions arrived at Acre, John of Ibelin went immediately to Beirut to ensure that the city could withstand an imperial attack, returning to face the Haute Cour.

He gave nominal commands to faithful adherents—Hermann of Salza, Odo of Montbéliard, Richard Filangieri—in order for Crusaders to avoid jeopardizing their positions in the eyes of the curia.

[58] Frederick hoped that a token show of force, a threatening march down the coast, would be enough to convince al-Kamil to honor a proposed agreement that had been negotiated some years earlier.

In January 1229, Frederick received notice that John of Brienne, serving the curia as rector of a Patrimony of Saint Peter,[59] had taken San Germano and was threatening Capua.

Hermann of Salza approached Gérold with a proposal of reconciliation, but the patriarch saw only deceit, trying to prevent Frederick's entry into Jerusalem by threatening excommunication of the army and placing the city under interdict.

[68] Still wearing his crown, Frederick proceeded to the palace of the Hospitallers where he met with the English bishops and members of the military orders to discuss the fortifications of the city.

Frederick obtained from the pope relief from his excommunication on 28 August 1230 with the Treaty of San Germano, and he returned to the Hospitallers and the Templars the goods confiscated in Sicily.

On the Muslim side, al-Kamil himself was pleased with the accord, but Arabic sources referred to the treaty as "one of the most disastrous events of Islam," laying the blame solely with the sultan.

[73] The ten-year expiration of Frederick's treaty with al-Kamil caused Pope Gregory IX to call for a new crusade to secure the Holy Lands for Christendom beyond 1239.

In the Ayyubid camp, the treaty allowed the sultan al-Kamil and his brother al-Ashraf to focus their energies into defeating their nephew an-Nasir Dā’ūd, emir of Damascus, capturing his capital city in June 1229.