PRESTER JOHN: A legendary Christian king of Asia, who in the twelfth century was supposed to have conquered the Mohammedans in a bloody battle and to have protected the crusaders. Bishop Otto of Freising, followed by Alberic, in his chronicle for 1145, relates that a bishop of Gabula told Pope Eugene III. of a Nestorian king and priest named Presbyter Johannes, who ruled "beyond Persia and Armenia," the double office being due to a confusion of kam ("priest") with khan ("prince"). In his chronicle on 1165, moreover, Alberic states that Prester John, "the king of the Indians," sent letters to various Christian rulers, especially to Manuel of Constantinople and the Roman Emperor Frederick. Influenced by rumors of such a king, Alexander III. sent his physician in ordinary in search of the monarch, directing his letter, dated at Venice Sept. 27, 1177, "to the king of the Indians, the most holy of priests," but the messenger disappeared without leaving a trace.

A new epoch for the legend began with the Dominican and Franciscan missions to the East after 1245. The majority of reports agreed that Prester John no longer lived but had fallen in battle with Genghis Khan, the chief authority for this form of the legend being the Franciscan Wilhelmus Rubruquis. On Jan 8, 1305, the archbishop of Peking, John of Monte Corvino (q.v.), told of a King George of the Nestorian sect, a descendant of the famous Prester John of India. This monarch had ruled in a land called Tenduch, twenty days distant, had become a convert to the Roman Catholic faith, and, after receiving minor orders, had ministered in his royal robes. This king, termed by Marco Polo the sixth after Prester John, had died in 1299. The fall of the Mongol dynasty in China in 1368 put an end to the missions in the East, but the way was already prepared for the third, or African, phase of the legend by the vague use of the term "India" and the accounts of a Christian kingdom of "Abascia" in middle India. This transfer from Asia to Africa was aided by the similarity of the names of the Abchases in the Caucasus (also called Abasi and Abassini) and the Abyssinians. The Roman Catholic Jordanus, bishop of Quilon in southern India, called the king of Ethiopia simply John. Envoys of this monarch appeared in Europe c. 1400, and when the Portuguese undertook to voyage to the East Indies, they were encouraged in great part by the fame of the realm of Prester John, and when they found the Christians of St. Thomas in Malabar, they fancied that region a Christian kingdom.

A careful study of medieval travels led to the identification with Prester John of Unk Khan, whom Rubruquis and others had declared to be the brother of a Nestorian King John, who had ruled over the Naymans, but had gained the throne of the Catai or Caracatai after the death of Coir Khan. Others saw in the Tibetan Lama an apostate descendant of the mythical king, and still others brought the so-called Christians of St. John into the discussion. In 1839 M. A. P. Avezac-Macaya investigated the legend of Prester John (Recueil de voyages et de memoires publié par la Société de Geographie, IV., 547-654), and identified the Coir Khan of Rubruquis with the Ghaur Khan, the founder of the kingdom of Qara-Khithay, who was a Buddhist, but apparently had many Nestorian subjects. This prince, called Yeliu Tashe by the Chinese, was succeeded in 1136 by his son Yeliu Yliei, and in 1155 by his grandson Tchiluku. In 1208 the latter made the Nayman Prince Kushluk his son-in-law, only to meet his death at the hands of his thankless protégé, who in his turn was killed in 1218 by Genghis Khan. Rubruquis took the title Ghaur Khan as a proper name, fused the first three princes into one, and finally gave ground to the confusion with Unk Khan, who was killed by Genghis Khan fifteen years before Kushluk.

According to Gustav Oppert Ghaur Khan or Kor Khan was changed by phonetic laws to Yor Khan, which was corrupted through the Hebrew Yohannan, and the Syriac Yuhanan into Johannes. It is a historic fact, moreover, that Kushluk's wife, the daughter of the last Ghaur Khan, was a Christian, and that descendants of this royal family who later ruled in Tenduch were also Christians and ruled over a Christian population.