Heraclius (ca. 575-641) was Byzantine emperor from 610 to 641. Ascending the throne when the empire seemed on the point of dissolution, he saved it from its immediate foes and gave it new institutional and cultural direction.

Born in Cappadocia, Heraclius was apparently of Armenian origins. His father, Heraclius, was a leading general under Emperor Maurice and became exarch (viceroy) of North Africa. When the regime of the usurper Phocas (602-610) degenerated into chaos, dissident elements in Constantinople urged the elder Heraclius to seize the throne; but the old exarch sent his son instead. The rebellion succeeded in overthrowing Phocas and enthroning Heraclius in October 610.

Because of Phocas's mismanagement, Heraclius faced a seemingly impossible situation. The Slavs and the Avars had overrun the Balkans and threatened anew the empire's remaining European territories. Meanwhile, the Sassanid king of Persia, Chosroes (or Khusru) II, began a war of conquest against the empire's...