Prester John. One of the most enduring tales of the Middle Ages was that of Prester John. It told of a Christian kingdom somewhere in Asia (or, later, Africa) that had been converted by and was ruled over by a benevolent theologian-king by the name of Prester John. Where and when the tale originated is not known, although some conjecture that it could have been associated with the legends of Saint Thomas's mission to India. However, soon after the Crusades were under way, the popularity of Prester John increased. The idea was that once the Holy Land was occupied and returned to Christianity, new Crusaders and explorers would be sent to seek out Prester John and unite his kingdom with the rest of Christendom. Later, when the Crusades proved to be unsuccessful, it was believed that Prester John would bring a military force to...