Constantine IV

Constantine IV took the throne in 668 with the Byzantine Empire reeling from decades of defeats and internal chaos. The Arabs had been advancing almost without check since the 620s, swallowing Syria, Egypt, North Africa. When they laid siege to Constantinople itself, he held the walls and broke them — a rare reversal that steadied an empire on the edge of collapse. He used the breathing room to settle a theological fight that had torn Byzantium apart for decades: in calling the Sixth Ecumenical Council, he ended the monothelitism controversy. He died on 10 July 685, after seventeen years in po…