The Fifth Crusade (1217–1221) was an attempt to take back Jerusalem by first conquering the powerful Muslim state in Egypt.
In spring 1213, Pope Innocent III issued the papal bull Quia maior, calling all of Christendom to join a new crusade. The kings and emperors of Europe, however, were preoccupied with fighting among themselves. Innocent did not want their help because previous crusades led by kings (the Second Crusade and the Third Crusade) had failed in the past. He ordered processions, prayers, and preaching to help organize the crusade, as these would involve the general population, the lower nobles, and knights.
The message of the crusade was preached in France by Robert of Courcon ; however, unlike other Crusades, not many French knights joined, as they were already fighting the Albigensian Crusade aganist the heretical Cathar sect in southern France.
In 1215 Innocent III called 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. Innocent wanted this crusade to be under the full control of the papacy, as the First Crusade was supposed to have been, in order to avoid the mistakes of the Fourth Crusade, which had been taken over by the Venetians. 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 himself.
Oliver of Cologne had preached the crusade in Germany, and Emperor Frederick II attempted to join in 1215. Frederick was the last monarch Innocent wanted to join, as Frederick was the only one capable of challenging the authority of the Papacy (and would do so in the years to come). Innocent, however, died in 1216. He was succeeded by Pope Honorius III, who barred Frederick from participating, but organized crusading armies led by Leopold VI of Austria and Andrew II of Hungary. They left for Acre in 1217, and joined John of Brienne, nominal king of Jerusalem, Hugh I of Cyprus, and Prince Bohemund IV of Antioch to fight against the Ayyubids in Syria. In Jerusalem, the walls and fortifications were demolished to prevent the Christians from being able to defend the city if they should reach it and take it. Muslims fled the city, afraid that there would be a repeat of the bloodbath of the First Crusade in 1099. The Ayyubids, however, were not interested in fighting. Nothing came of this, and Andrew, Bohemund, and Hugh returned home in 1218. Later in 1218 Oliver of Cologne arrived with a new army, and with Leopold and John they discussed attacking Damietta in Egypt. To accomplish this they allied with Kay Kaus I , the Seljuk Sultan of Rum in Anatolia, who attacked the Ayyubids in Syria in an attempt to free the Crusaders from fighting on two fronts.
In June of 1218 the crusaders began their siege of Damietta, and despite resistance from the unprepared sultan al-Adil, the tower outside the city was taken on August 25. They could not gain Damietta itself, and in the ensuing months diseases killed many of the crusaders, including Robert of Courcon. Al-Adil also died and was succeeded by Al-Kamil. Meanwhile, Honorius III sent Pelagius of Albano to lead the crusade in 1219. Al-Kamil tried to negotiate a peace with the crusaders, but Pelagius would not accept these offers. In August, Francis of Assisi, then a subordinate of Pelagius, tried to open negotiations with al-Kamil and Pelagius, but had no success. By November, the crusaders had worn out the sultan's forces, and were finally able to occupy the port.
Immediately the papal and secular powers fought for control of the town, with John of Brienne claiming it for himself in 1220. Pelagius would not accept this and John returned to Acre later that year. Pelagius hoped Frederick II would arrive with a fresh army, but he never did; instead, after a year of inactivity in both Syria and Egypt, John of Brienne returned, and the crusaders marched south towards Cairo in July of 1221.
By now al-Kamil was able to ally with the other Ayyubids in Syria, who had defeated Kay Kaus I. The crusaders march to Cairo was disastrous; Al-Kamil simply flooded the Nile, cutting the crusaders' access to the roads, and then surrounded them, forcing Pelagius to agree to a peace. In September al-Kamil retook Damietta, and the crusaders left for home, having failed to accomplish anything of importance in their three years in Egypt.