The Two Cities, A Chronicle of Universal History
Inspired by civil unrest in Germany and written shortly after the fall of Edessa in 1143, Otto of Freising's Historia de duabus civitatibus has come to be known for providing an important early source on the figure of Prester John.
Oddly enough, this vital information is nothing more than an a recorded anecdote from 1145 that tells of a colleague of Otto's called Hugh of Jabala, a bishop from Lebanon, who was relaying news of a promising Nestorian Christian prince, Iohannes.
According to Otto, widely reputed to be a trustworthy historian, this Iohannes, hailing from the distant East of the Magi, had recently conquered Persia and headed West to assist crusaders in their defense of the Holy Land. Unfortunately, Otto relates, a flooded Tigris River prevented him from aiding his Latin Christian brethren.
Although this rumor spawned the centuries-long belief in an Eastern potentate capable of uniting Christendom, the initial account of an Eastern anti-Islamic leader was later revealed to refer to the deeds of the Qara Khitai, a nomadic Chinese tribe descending from Manchuria.
Nevertheless, despite historical mistranslation and Iohannes's failure to reach even Byzantium, this rumor helped set in motion a belated European recognition of the world beyond the Tigris, a world that remained controlled by a heterodoxically Christian sovereign.
From Slessarev, Prester John: The Letter and the Legend (pp. 27-28):
He [i.e. Hugh] related also that not many years before a certain John, a king and priest who dwells beyond Persia and Armenia in the uttermost East and, with all his people, is a Christian but a Nestorian, made war on the brother kings of Persians and Medes, called Samiardi, and stormed Ekbatana (the seat of their kingdom) of which mention has been made above.
When the aforesaid kings met him with an army composed of Persians, Medes and Assyrians a battle ensued which lasted for three days, since both parties were willing to die rather than turn in flight. Prester John, for so they are accustomed to call him, putting the Persians to flight with dreadful carnage finally emerged victorious.
He said that after this victory the aforesaid John moved his army to the aid of the Church in Jerusalem. But that when he had reached the river Tigris and was unable to transport his army across that river by any evidence he turned towards the north, where, he had learned, this stream was frozen over on account of the winter’s cold.
When he had tarried there for several years without, however, seeing his heart’s desire realized (the continued mild weather prevented it), and lost many of his soldiers because of the unfamiliar climate he was forced to return home.
It is said that he is a lineal descendent of the Magi, of whom mention is made in the Gospel, and that, ruling over the same peoples which they governed, he enjoys such great glory and wealth that he uses no scepter save one of emerald. Inflamed by the example of his fathers who came to adore Christ in his manger, he hand planned to go to Jerusalem but my reason aforesaid he was prevented—so men say. But enough of this.”
In analyzing this anecdote that arguably sparked the Prester John fever across Europe, Niayesh (p. 157) notes the structural "ambivalence" of Hugh's account, noting that his story was "caught half-way between the pagan past of classical authorities and the present of Christian Crusaders":
[Prester John] is vaguely located in extremo Oriente and is made to fight the long extinct nations of the Medes and Assyrians, rather than directly facing contemporary 'Saracens.' He beats them back to Ecbatana, which was the ancient capital of the the Medes vanquished and destroyed by Cyrus the Great in 550 BCE, i.e. about twelve centuries before Otto wrote his chronicle. As for the mysterious name of John's kingly adversaries, the 'Samiardi', it recalls the Persian 'Smerdis', name of the murdered brother of Cambyses, son and heir to Cyrus the Great.
Brewer edits and translates the relevant passages of the chronicle (pp. 43-45).
