John is the first ruler of Trebizond for whom we know more than a few incidents and hints; there is enough information to compose a connected narrative of the first part of his reign. The chronicle of Michael Panaretos, which is often terse and even cryptic, is relatively full for John's reign, and external sources add further details to Panaretos' account. Emperor John II faced many challenges to his rule, which partly explains his marriage to the daughter of the Byzantine emperor Michael VIII Palaiologos.