 Under Frederick II , a Sixth Crusade was launched , capitalizing on the ongoing internal strife between al @-@ Kamil of Egypt and al @-@ Mu 'azzam of Syria . Subsequently , al @-@ Kamil offered Jerusalem to Frederick to avoid a Syrian invasion of Egypt , but the latter refused . Al @-@ Kamil 's position was strengthened when al @-@ Mu 'azzam died in 1227 and was succeeded by his son an @-@ Nasir Dawud . Al @-@ Kamil continued negotiations with Frederick II in Acre in 1228 , leading to a truce agreement signed in February 1229 . The agreement gave the Crusaders control over an unfortified Jerusalem for over ten years , but also guaranteed Muslims control over Islamic holy places in the city . Although the treaty was virtually meaningless in military terms , an @-@ Nasir Dawud used it to provoke the sentiments of Syria 's inhabitants and a Friday sermon by a popular preacher at the Umayyad Mosque " reduced the crowd to violent sobbing and tears " . 
