I apologise if this question has been asked before. I also admit that this (as well as most Muslim history) isn't my area of expertise, but, if Nur ad-Din hadn't died in 1174, could he have defeated Saladin and taken Egypt for himself as he had originally intended? The two men had already assembled their armies. In addition, especially if the fighting is drawn-out, the continued divide between Syria and Egypt could have given the Crusader states some needed breathing space.
Any thoughts?