John II Komnenos, Emperor of the Romans

John II Komnenos (9th January 1113-15th April 1180) was Roman Emperor from January 1152 until his death, although he had served as co-Emperor to his father Manuel and grandfather Isaac  from the age of four. He was the fifth member of the House of Komnenos to rule as Emperor. John was initially succeeded by his grandson Michael, but civil war soon broke out between various of his relatives, notably his wife, Theodora of Hungary.

A religious man, John claimed much of the credit for the ecclesiastical achievements of the Eighth Ecumenical Council in 1150, which he largely presided over. Despite a personal distaste for war, John's reign was without doubt the most violent since that of Basil II, involving rebellious generals, uprisings by local populations in Europe, and the armed conquest of Hungary and much of Palestine. John's wars great increased the size and prestige of the empire, but were very costly, and seem to have brought an end to the period of economic growth that characterised his father's reign.

War and turmoil took its toll on John, who died a madman. His reign, despite its outward successes, was almost immediately followed by further upheval for which John's policies were probably largely responsible.