Heraclius (hĕrəklĪˈəs, hĭrăkˈlēəs) [key], c.575–641, Byzantine emperor (610–41). The son of a governor of Africa, he succeeded the tyrant Phocas, whom he deposed and had executed. In the early years of his reign Avars and Bulgars threatened, attacking even Constantinople, and the Persians conquered Syria, Palestine, and Egypt. In three costly campaigns (622–28) Heraclius recovered the provinces from the Persians, but they fell (629–42) to the Muslim Arabs. He sought to reconcile the Monophysites with the Orthodox Church; this attempt led to the compromise of Monotheletism, which was rejected by both sides. Heraclius began the reorganization of the empire into military provinces ( themes ). He was succeeded briefly by his son Constantine III and then by his grandson Constans II.