Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. John, surnamed Mystacon, "the mustachioed", was a prominent East Roman (Byzantine) general in the wars with Sassanid Persia during the reigns of Byzantine emperors Tiberius II (r. 578-582) and Maurice (r. 582-602). A native Thracian, John first appears in history as a general in Roman Armenia in 579, along with Cours. If not already holding the post of magister militum per Armeniam at that time, he had been elevated to it by 582, when he was named magister militum per Orientem by the newly-crowned Maurice.