Constantine IV

Constantine IV (Greek: Κωνσταντῖνος, romanized: Kōnstantīnos; Latin: Constantinus; c. 650 – 10 July 685), called the Younger (Greek: ὁ νέος, romanized: ō Néos) and often incorrectly the Bearded (Greek: ὁ Πωγωνᾶτος, romanized: ō Pōgōnãtos) out of confusion with his father, was Byzantine emperor from 668 to 685. His reign saw the first serious check to nearly 50 years of uninterrupted Arab expansion, most notably his successful defence of Constantinople, and the temporary stabilization of the Byzantine Empire after decades of war, defeats, and civil strife. His calling of the Sixth Ecumenical Council saw the end of the monothelitism controversy in the Byzantine Empire; for this, he is venerated as a saint in the Eastern Orthodox Church, with his feast day on September 3.

Source: Wikipedia — https://en.wikipedia.org/wiki/Constantine_IV