Coat of arms of the Latin Empire of Constantinople.
During the Fifth Crusade (1218–1221) he was a prominent figure. The legate Pelagius of Albano, however, claimed the command; and insisting on the advance from Damietta, in spite of John's warnings, he refused to accept the favourable terms of the sultan, as the king advised, until it was too late. After the failure of the crusade, King John came to the West to obtain help for his kingdom. In 1223 he met Pope Honorius III and the emperor Frederick II at Ferentino, where, in order that he might be connected more closely with the Holy Land, Frederick was betrothed to John's daughter Isabella, now heiress of the kingdom. After the meeting at Ferentino, John went to France and England, finding little consolation; and thence he travelled to Santiago de Compostela, where King Alfonso IX of Leon offered him the hand of one of his daughters and the promise of his kingdom. John passed over Alfonso's eldest daughter and heiress in favor of a younger daughter, Berenguela of Leon. After a visit to Germany he returned to Rome (1225). Here he received a demand from Frederick II (who had now married Isabella) that he should abandon his title and dignity of king, which, so Frederick claimed, had passed to himself along with the heiress of the kingdom. John avenged himself on Frederick, by commanding the papal troops which attacked southern Italy during the emperor's absence on the Sixth Crusade (1228–1229).
After this last feat of arms, which has perhaps been exaggerated by the Latin chroniclers, who compare him to Hector, Roland and the Maccabees, John died in the habit of a Franciscanfriar. An aged paladin, he was somewhat uxorious and always penniless, and a typical knight errant whose wanderings led him all over Europe, and planted him successively on the thrones of Jerusalem and Constantinople.