575-641. Byzantine emperor from 610. His reign marked the revival of the Eastern Empire. In 611 Persian attackers captured Edessa, Apamea, and Antioch. Heraclius fought the Persians throughout his reign, reorganizing his army for efficiency and establishing the “theme” as the empire's basic military and administrative unit. Antioch was his headquarters until about 636; the center of the empire survived despite the loss of Syria and Egypt to the Arabs. Fearing that Monophysitism in Syria, Armenia, and Egypt would bring support to the Persians by alienating the indigenous population from the central government, he tried to reconcile Monophysite and Chalcedonian views on Christology by proposing a Monothelite solution in 633: Christ had one divine human will. Sergius of Constantinople was his chief religious counselor (drawing on Cyril and Dionysius the Areopagite). This effort began as early as 628, when occupied territories were freed. Negotiations pivoted on Athenasius, Jacobite patriarch of Antioch, but he died in 631. Strong opposition to the plan focused in a monk named Sophronius, later patriarch of Jerusalem, and in Honorius of Rome.

See Ecthesis.