 Al @-@ Adil aroused open hostility from the Hanbali lobby in Damascus for largely ignoring the Crusaders , having launched only one campaign against them . Al @-@ Adil believed that the Crusader army could not be defeated in a direct fight . Prolonged campaigns also involved the difficulties of maintaining a coherent Muslim coalition . The trend under al @-@ Adil was the steady growth of the empire , mainly through the expansion of Ayyubid authority in al @-@ Jazira and Armenia . The Abbasids eventually recognized al @-@ Adil 's role as sultan in 1207 . A Crusader military campaign was launched on 3 November 1217 , beginning with an offensive towards Transjordan . Al @-@ Mu 'azzam urged al @-@ Adil to launch a counter @-@ attack , but he rejected his son 's proposal . In 1218 , the fortress of Damietta in the Nile Delta was besieged by the Crusaders . After two failed attempts , the fortress eventually capitulated on 25 August . Six days later al @-@ Adil died of apparent shock at Damietta 's loss . 
