As he was born to a reigning emperor, he had the status of a porphyrogennetos. John was a pious and dedicated monarch who was determined to undo the damage his empire had suffered following the Battle of Manzikert , half a century earlier. John has been assessed as the greatest of the Komnenian emperors.
John's campaigns fundamentally changed the balance of power in the east, forcing the Turks onto the defensive; they also led to the recapture of many towns, fortresses and cities across the Anatolian peninsula. In the southeast, John extended Byzantine control from the Maeander in the west all the way to Cilicia and Tarsus in the east. In an effort to demonstrate the Byzantine ideal of the emperor's role as the leader of the Christian world, John marched into Muslim Syria at the head of the combined forces of Byzantium and the Crusader states ; yet despite the great vigour with which he pressed the campaign, John's hopes were disappointed by the evasiveness of his Crusader allies and their reluctance to fight alongside his forces.
Under John, the empire's population recovered to about 10 million people. In particular little is known of the history of John's domestic rule or policies. The Latin historian William of Tyre described John as short and unusually ugly, with eyes, hair and complexion so dark he was known as 'the Moor '.
Both his parents were unusually pious and John surpassed them. Members of his court were expected to restrict their conversation to serious subjects only. The food served at the emperor's table was very frugal and John lectured courtiers who lived in excessive luxury. His speech was dignified, but he engaged in repartee on occasion. All accounts agree that he was a faithful husband to his wife, an unusual trait in a medieval ruler. Despite his personal austerity, John had a high conception of the imperial role and would appear in full ceremonial splendour when this was advantageous.
John was famed for his piety and his remarkably mild and just reign. He is considered an exceptional example of a moral ruler, at a time when cruelty was the norm. He is reputed never to have condemned anyone to death or mutilation. For this reason, he has been called the Byzantine Marcus Aurelius.
