Sixth Crusade
The excommunicated Emperor Frederick II, without fighting, negotiated with Sultan al-Kamil of Egypt to receive Jerusalem for ten years.
Giovanni Villani , Chronica, 14. Jahrhundert, Biblioteca Apostolica Vaticana, Rom Cod. Chigi L VIII 296, fol. 75r. · Public domain · Source
Frederick II had delayed so long that the pope excommunicated him, and he reached Acre in 1228 still under the ban. Knowing Arabic and at home in Islamic culture, he made a treaty at Jaffa in February 1229 with al-Kamil, who was then at odds with his relatives in Syria: Jerusalem, Bethlehem and Nazareth were returned, while the Muslim shrines on the Temple Mount (Haram al-Sharif) stayed in Muslim hands.
He crowned himself in the Church of the Holy Sepulchre and was condemned on both sides. Jerusalem was sacked by Khwarazmian troops in 1244 and never returned to crusader rule.