While the Fourth Crusade turned its attention to Constantinople (1203), Islām had another fifteen years of truce, which enabled al-Malik al-‘Adil to unite his brother Saladin’s kingdom firmly under his own control and to organize as one empire the Ayyubid domains from Egypt to Mesopotamia. The new Crusade had its eyes on Egypt itself, as the heart of Muslim resistance at a time when the Mongol threat loomed in the East, soon to grow to its full, terrible stature. Ibn al-Athīr, with his usual breadth of vision, rises above the level of a local chronicler to consider the fate of Islām as a whole, and perceives the gravity of the double threat. He expresses it both in his dramatic description of the Mongol invasion and in this history of the Fifth Crusade, uniting in one cogent account the four years of the Egyptian campaign (1217-21). As a complement to Ibn al-Athīr’s account we include that of Ibn Wasil, an Ayyubid historian until recently almost inaccessible in his original form and therefore little studied.