Which crusade was led by Frederick II and recovered Jerusalem by treaty?

The Sixth Crusade was led by Frederick II and recovered Jerusalem through a treaty. Unlike most major Crusades, it achieved its central objective with diplomacy rather than a decisive battlefield victory.

Frederick, the Holy Roman Emperor and king of Sicily, negotiated with al-Kamil, the Ayyubid sultan of Egypt. Their agreement, known as the Treaty of Jaffa, was concluded in 1229. It returned Jerusalem, Bethlehem, Nazareth, and a corridor to the coast to the Crusaders, while leaving the city’s Muslim holy places under Muslim administration.

The expedition was unusual for another reason: Frederick was excommunicated by Pope Gregory IX when he departed, and the campaign involved very little fighting. Frederick’s claim to the crown of Jerusalem also came through his marriage to Isabella II, the kingdom’s heiress. The arrangement lasted only temporarily; Jerusalem was recaptured by Muslim forces in 1244. The Fifth Crusade had failed in Egypt, while the Seventh Crusade was led by Louis IX of France, not Frederick.