 Al @-@ Kamil proclaimed himself sultan in Cairo , while his brother al @-@ Mu 'azzam claimed the throne in Damascus . Al @-@ Kamil attempted to retake Damietta , but was forced back by John of Brienne . After learning of a conspiracy against him , he fled , leaving the Egyptian army leaderless . Panic ensued , but with the help of al @-@ Mu 'azzam , al @-@ Kamil regrouped his forces . By then , however , the Crusaders had seized his camp . The Ayyubids offered to negotiate for a withdrawal from Damietta , offering the restoration of Palestine to the Kingdom of Jerusalem , with the exception of the forts of Mont Real and Karak . This was refused by the leader of the Fifth Crusade , Pelagius of Albano , and in 1221 , the Crusaders were driven out of the Nile Delta after the Ayyubid victory at Mansura . 
