https://en.wikipedia.org/wiki/Medieval_Christian_views_on_MuhammadDuring the Early Middle Ages, the Christian world largely viewed Islam as a Christological heresy and Muhammad as a false prophet. By the Late Middle Ages, Islam was more typically grouped with heathenism and Muhammad viewed as inspired by the devil. A more relaxed or benign view of Islam only developed in the modern period, after the Islamic empires ceased to be an acute military threat to Europe, see Orientalism.
The earliest documented Christian knowledge of Muhammad stems from Byzantine sources, written shortly after Muhammad's death in 632. With the Crusades of the High Middle Ages, and the wars against the Ottoman Empire during the Late Middle Ages, the Christian reception of Muhammad became more polemical, moving from the classification as a heretic to depiction of Muhammad as a servant of Satan or as the Antichrist, who will be suffering tortures in Hell.
Interesting article. Much more:
https://en.wikipedia.org/wiki/Medieval_Christian_views_on_Muhammad
