Heraclius , a Roman emperor of the East, born in Cappadocia about A. D. 575, died early in 641. He was the son of Heraclius, exarch of Africa, and first appeared in a public capacity in 610, when his father sent him with a fleet to besiege Constantinople, and dethrone the tyrant Phocas. This enterprise he accomplished, and was himself chosen to fill the vacant throne. At the accession of Heraclius, the empire was in a deplorable condition. The barbarians of the north were laying waste its European provinces, while the Persians, under Chosroes H., were overrunning and ravaging those of the east. The first object of the new emperor was to protect his European dominions and to make provision for their future security. The king of the Avars having withdrawn from before Constantinople, after treacherously slaying or taking captive immense numbers of citizens who had come out to witness an interview between him and Heraclius, the latter allotted that part of Hlyricum bordering on the Adriatic and the Danube, which had been depopulated, to the Serbs and Croats, in order that they might serve as a barrier to his N. W. frontier.
Then, turning his attention eastward, as soon as he considered his army sufficiently disciplined to take the field, he placed himself at its head, and sailing from the Bosporus in 622, landed in Cilicia, and encamped on the plain of Issus, where he defeated a large Persian force. From Cilicia he fought his way into Pontus, and afterward returned to Constantinople. In the following spring he landed at Trapezus (Trebizond) with another army, whence, marching through the regions of the Caucasus, he penetrated into Media, forming alliances and destroying the temples of the Magi as he proceeded. This campaign was closed by a second brilliant victory over the Persians commanded by Chosroes in person. In 625 he invaded Mesopotamia, and returning through Cilicia, gained a third great victory over the Persians on the river Larus, where he slew with his own hand a gigantic barbarian whom all feared to encounter. The last campaign of this war was by far the most glorious. Constantinople was besieged by a great host of Persians and Avars, but instead of going to its relief Heraclius marched into the very heart of the Persian empire, overthrew the enemy in a great battle near Nineveh in December, 627, took Dastagerd, the favorite residence of Chosroes, and plundered the royal palaces in the vicinity of untold treasure.
In 628, Chosroes having been put to death by his son Siroes, the latter acceded to a treaty which closed the war and restored to Heraclius the provinces wrested from his predecessor. But at Edessa, as he was returning from the war, an ambassador from Mohammed summoned him to embrace the faith of the prophet. Heraclius made a treaty of amity with the Arabian potentate; but in a little time a war broke out between the Arabs and the eastern emperor, in which Syria, Palestine, and Egypt were wrested from the latter. Heraclius took no part personally in this contest, but spent his latter days in luxurious ease in Constantinople.