Note 191 — A NARRATIVE OF ITALIAN TRAVELS IN PERSIA.
Eugene Armand Roy translation
Calo Johannes, or Black John, brother of David, last Christian Emperor of Trebizond, was of the noble family of the Comneni, which became extinct with them. Trebizond was taken in 1461 by Mahomet II, Sultan of the Turks. Uzun Hassan had married Despina while still Prince of Diarbekr, before he had gained the throne.