The loss of the tower was a great shock to the Ayyubids, and the sultan al-Adil died soon thereafter. He was succeeded as sultan by his son al-Kamil. Further offensive action by the Crusaders would have to wait until the arrival of additional forces, including legate Pelagius with a contingent of Romans. A group from England arrived shortly thereafter. By February 1219, the Crusaders now had Damietta surrounded, and al-Kamil opened negotiations with the Crusaders, asking for envoys to come to his camp. He offered to surrender the kingdom of Jerusalem, less the fortresses of al-Karak and Krak de Montréal, guarding the road to Egypt, in exchange for the evacuation of Egypt. John of Brienne and the other secular leaders were in favor of the offer, as the original objective of the Crusade was the recovery of Jerusalem. But Pelagius and the leaders of the Templars and Hospitallers refused. Later, Francis of Assisi arrived to negotiate unsuccessfully with the sultan. In November 1219, the Crusaders entered Damietta and found it abandoned, al-Kamil having moved his army south. In the captured city, Pelagius was unable to prod the Crusaders from their inactivity, and many returned home, their vow fulfilled. Al-Kamil took advantage of this lull to reinforce his new camp at Mansurah, renewing his peace offering to the Crusaders, which was again refused. Frederick II sent troops and word that he would soon follow, but they were under orders not to begin offensive operations until he had arrived. In July 1221, Pelagius began to advance to the south. John of Brienne argued against the move, but was powerless to stop it. Already deemed a traitor for opposing the plans and threatened with excommunication, John joined the force under the command of the legate. In the ensuing Battle of Mansurah in late August, al-Kamil had the sluices along the right bank of the Nile opened, flooding the area and rendering battle impossible. Pelagius had no choice but to surrender. The Crusaders still had some leverage as Damietta was well-garrisoned. They offered the sultan a withdrawal from Damietta and an eight-year truce in exchange for allowing the Crusader army to pass, the release of all prisoners, and the return of the relic of the True Cross. Prior to the formal surrender of Damietta, the two sides would maintain hostages, among them John of Brienne and Hermann of Salza for the Franks side and