Excerpts from Books and Wikipedia
"His rise to power began in 608, when he and his father, Heraclius the Elder, the exarch of Africa, led a revolt against the unpopular usurper Phocas. Heraclius's reign was marked by several military campaigns. The year Heraclius came to power, the empire was threatened on multiple frontiers. Heraclius immediately took charge of the Byzantine–Sasanian War of 602–628. The first battles of the campaign ended in defeat for the Byzantines; the Persian army fought their way to the Bosphorus but Constantinople was protected by impenetrable walls and a strong navy, and Heraclius was able to avoid total defeat. Soon after, he initiated reforms to rebuild and strengthen the military. Heraclius drove the Persians out of Asia Minor and pushed deep into their territory, defeating them decisively in 627 at the Battle of Nineveh. . . . Heraclius lost many of his newly-regained lands to the Muslim conquests. Emerging from the Arabian Peninsula, the Muslims quickly conquered the Sasanian Empire. In 634 the Muslims marched into Roman Syria, defeating Heraclius's brother Theodore. Within a short period of time, the Arabs conquered Mesopotamia, Armenia and Egypt." [Wikipedia]