The Muslims were not then driven back out of France; in fact, they remained in Narbonne and Septimania for another 27 years, but eventually they pulled back across the Pyrenees, solidifying their control of the Iberian Peninsula. And as we all know, the Christians of Spain did not quietly acquiesce in that Muslim conquest, but spent 770 years slowly liberating themselves from the Muslims, in what entered history as the Reconquista.

The final victory over the Muslims came with the conquest of Grenada in 1492. The Christians of Europe in the medieval period were keenly aware of the loss of all that vast territory, peopled by Christians, which Muslims had seized in Spain, North Africa, and the Middle East, and knew, too, that Arab armies were elsewhere on the move, pushing eastward against the Persians of the Sasanian Empire and threatening Byzantium. The Christians of Europe were constantly reminded of an ever-present threat of Islam, as reports would reach them of new Muslim victories.

And Muslim slavers raided Christian shipping in the Mediterranean, and attacked villages along the coasts not only of that inland sea, but also in the Atlantic, along the east coast of France and as far north as the Netherlands. Those raiders even reached Ireland and, in 1627, on one occasion, a Muslim raiding party even got as far north as Iceland. (To be precise, there were actually two simultaneous raiding parties in Iceland, one from Algiers, and one from Sale, in Morocco).

Those North African raiders came to be known as the Barbary Pirates; they became a real menace to Christian ships and seamen in the Mediterranean, and growing Western naval power, including especially that of the young American Republic, finally put paid to these Barbary Pirates in the early 19th century. During all those years of an ascendant Islam, the Europeans consoled themselves with stories of a fabulous kingdom of Nestorian Christians that existed on the other side of the Muslim domains. The powerful Christian king who ruled over this mysterious domain was known as Prester John.

The legend of Prester John lasted, in the collective European imagination, from the 12th to the 17th centuries. His mythical realm was first placed in India, both because that fabulous land had already established itself in European minds as full of wonders, and because of the reports, often exaggerated, of the evangelical successes of Nestorian Christians in that distant country.

Later, when the Mongols arrived in the West, and under Hulegu Khan conquered Baghdad in 1258, where they destroyed not just the city but the Abbasid Caliphate, Europeans imagined that Prester John’s kingdom was not in India, but to be found somewhere in Central Asia, among those same Mongols who, because they were known not to be Muslims, were assumed to be Christians (the Europeans in this period had hardly heard of Buddhists), and therefore as potential allies of Europe’s Christians against the ever-threatening Muslims.

And finally, after the Europeans discovered that the Mongols had converted to Islam, Prester John was moved yet again, in the fertile imaginations of Europeans, now to Africa, where it was reported by Portuguese explorers that his Nestorian Kingdom was established in Ethiopia, for that land, too, was famous as a Christian kingdom that, amidst so many lands to which Islam had spread and where Islam now dominated, had managed to hold out.