Crusade that came close to achieving it's objective, but failed due to the intransigence of Cardinal Pelagius, the papal legate. Frederick II of Germany promised to lead the crusade, but in the event did not take part, and when the crusaders first arrived in the Holy Land, they came under the command of John of Brienne, king of Jerusalem. Jerusalem itself was at this point under Egyptian control, and the crusader plan was to attack Egypt in order to force the hand over of key areas of Palestine. Early in 1218, the crusade finally moved, landing at Damietta, to find themselves facing Malik al-Kamil, the son of the sultan, and a future sultan himself, with perhaps 70,000 men, twice the number of crusaders. However, the crusaders were able to invest Damiette, which held out for a year and a half, only falling in November 1219. Meanwhile, Cardinal Pelagius had arrived, and in the absence of Frederick insisted on taking command of the crusade. The crusaders had been reinforced, and now numbered 46,000 men. By now it was clear that the Egyptians were prepared to negotiate, but in 1221 Pelagius decided to march on Cairo, through the inundation of the Nile, and the heat of summer. The crusaders finally came to a halt in July 1221 near Mansura, their path blocked by the Ashmoun Canal. At this point, the crusaders had a chance to gain their objective - the Egyptians offered to surrendered Jerusalem, and other Christian sites in Palestine, in return for the return of Damietta. Much to the dismay of John of Brienne, Pelagius demanded more land, and while negotiations dragged on and then failed, the Egyptians moved against the crusaders supply line to Damietta, while an attempt to cross the Ashmoun canal failed. Having had the chance to gain Jerusalem, the crusaders were now forced to accept Egyptian terms, surrendering Damietta in return for a few relics, of little value to the Moslem Egyptians, and safe passage back to the coat.