History of the Crusades/The Sixth Crusade

Background
After the failure of the Fifth Crusade, the Papacy was unpleased with Frederick II, whose failure to commit and constant delays were considered to have caused the failure of the crusade. Frederick II married the daughter of the King of Jerusalem, and it seemed that he would finally go on a crusade 1227 but once again, he turned back. After this, Gregory IX excommunicated Frederick II for failing to commit to his crusading vows. Frederick however, was undeterred and was determined to gain Jerusalem over which he had a claim.

Events of the Crusade
Frederick II began his unsanctioned crusade in 1228 and sailed for Jerusalem. Frederick was deeply disliked by many of the crusaders in Acre, as the pope had declared him an enemy of the faith. Frederick negotiated with al-Kamil and there was very little fighting before a treaty was arrived at. Jerusalem was to be given to Frederick but the city was not to be fortified and Muslims were to be allowed to remain and have their own government as well as keep control over the mosques. Frederick entered Jerusalem crowned himself King of Jerusalem. The reception of the other crusaders toward Frederick was poor. He was seen to have only obtained a technical victory by consorting with the Muslims, and since Jerusalem was to remain defenseless, this was seen as a hollow victory. Although he was now King of Jerusalem, he was deeply unpopular among those who lived there.