Heraclius was born to an Armenian family from Cappadocia. His father was a skilled general and later Exarch of Africa, and Heraclius too rose quickly through the ranks after joining the army. In 608 AD both Heraclii renounced their loyalty to Emperor Phocas, who had usurped the throne from Maurice six years earlier, and in 610 the younger Heraclius seized Constantinople by stealth and was acclaimed Emperor by the people and the senate.
The most immediate task was to settle the war against the Persians who, during the crisis, had captured Mesopotamia and Syria. Over the next 15 years the Persian Emperor, Khusrau, also conquered Egypt and the Holy Land and penetrated far enough into Anatolia to lay siege to Constantinople itself in 626. However, the failure of the siege fatally weakened the Persian army, allowing Rome to reconquer all the lost territories by the year 628.
The next few years were spent rebuilding and reorganising. In 630 Heraclius received a letter from the Patriarch of Alexandria informing him of the success of Islam among the Arabs, and barely a month later he received another letter from the Prophet Muhammad himself. This second message emphasised Islam's strict monotheism and invited the emperor to convert - intriguing him enough that, two years later, he himself journeyed to Arabia to witness Muhammad's teachings for himself.
Conversion to Islam
Heraclius journeyed in disguise, arriving in Mecca in time to witness Muhammad's Farewell Sermon, immediately after which he professed his belief in Muhammad's prophethood. After the Prophet died, Heraclius revealed himself and quickly set about forming alliances and learning more about Islam. It was at his urging that Ali pressed his claim to the Caliphship. In 633 he returned to Constantinople after arranging for hundreds of missionaries to do their work in Syria and Egypt, and once back in the capital he called for an Ecumenical Council of the Church in order to debate the Islamic question.
The Council narrowly voted to recognise Islam as the sole orthodox doctrine, but its decision provoked a schism within the Church and triggered uprisings across the Empire. From 635-638 Heraclius fought a vicious civil war against his own brother, Theodorus, and his victory secured the place of Islam in Romania for a generation. Almost simultaneously, he was forced to intervene in Arabia to halt the Persian war machine that was trying to reestablish its hegemony over the eastern coast..
The immense costs of fighting two wars at once, so soon after the 26-year-long war with Persia that had ended less than a decade before, crippled the Empire for years and rendered it unable to prevent the West from breaking away.
Heraclius' last years were relatively peaceful, though he did not live long enough to solve the financial crisis. He died in 641 and was succeeded by his eldest son, Constantine III.