The portrayal of Saracens as quasi‐Jewish killers of Christ enables Christians not only to glorify those who defeat them in battle but also to inspire new military campaigns. The Muslim chronicler Izz al‐Din Ibn al‐Athir provides a vivid example of such rhetoric when recounting what happened after Muslim forces retook Jerusalem in 1187.

Ibn al‐Athir, perhaps drawing on firsthand knowledge, reports that the city’s patriarch aroused fellow Franks to avenge this loss by making a picture of Jesus that “portrayed Christ (peace be upon him) along with an Arab, depicted as beating him. They put blood on the portrait of Christ and said to the people, ‘This is Christ with Muhammad, the prophet of the Muslims, beating him. [Muhammad] has wounded and slain him.’”

Ibn al‐Athir inserts the customary Islamic honorific for Jesus, whom Muslims revere as a messenger of God, but provides no further editorial commentary: he trusts that his Muslim audience will recognize the preposterous nature of the allegation that Muhammad killed Christ. Preposterous though it is, this propaganda builds on longstanding Frankish rhetoric associating Muslims with Christ’s persecutors, and it provides powerful religious motivation for Christian warriors to avenge the maltreatment of their God.

Ibn al‐Athir credits this propaganda with raising “more men and money than there would be any way of counting” toward what academic historians call the Third Crusade; “even the women,” he emphasized, “answered the call in great numbers.” If Ibn al‐Athir is reliable, he provides valuable evidence regarding the broad impact of religious rhetoric designed to appeal to a specific subset of Christian society, namely fighting men.¹²

(Source.)