Pope Innocent III Summons The Fourth Lateran Council
The message of the crusade was preached in France by Robert of Courçon; however, unlike other Crusades, not many French knights joined, as they were already fighting the Albigensian Crusade against the heretical Cathar sect in southern France.
In 1215 Pope Innocent III summoned the Fourth Lateran Council, where, along with the Latin Patriarch of Jerusalem, Raoul of Merencourt, he discussed the recovery of the Holy Land, among other church business. Pope Innocent wanted it to be led by the papacy, as the First Crusade should have have been, in order to avoid the mistakes of the Fourth Crusade, which had been taken over by the Venetians. Pope Innocent planned for the crusaders to meet at Brindisi in 1216, and prohibited trade with the Muslims, to ensure that the crusaders would have ships and weapons. Every crusader would receive an indulgence, including those who simply helped pay the expenses of a crusader, but did not go on crusade themselves.
By processions, prayers, and preaching, the Church attempted to set another crusade afoot, and the Fourth Council of the Lateran (1215) formulated a plan for the recovery of the Holy Land. In the first phase, a crusading force from Austria and Hungary joined the forces of the king of Jerusalem and the prince of Antioch to take back Jerusalem. In the second phase, crusader forces achieved a remarkable feat in the capture of Damietta in Egypt in 1219, but under the urgent insistence of the papal legate, Pelagius, they then launched a foolhardy attack on Cairo in July of 1221. The crusaders were turned back after their dwindling supplies led to a forced retreat. A night-time attack by the ruler of Egypt, the powerful Sultan Al-Kamil, resulted in a great number of crusader losses and eventually in the surrender of the army. Al-Kamil agreed to an eight-year peace agreement with Europe.
Wikipedia: Fifth Crusade
Wikipedia: Fourth Council Of The Lantern