Heraclius
Heraclius Eastern Roman emperor from 610 to 641. His rise to energy to direct or established began in 608, when he as living as his father, Heraclius a 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 multinational frontiers. Heraclius immediately took charge of the Byzantine–Sasanian War of 602–628. The number one 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 as well as a strong navy, in addition to Heraclius was excellent 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. The Persian king Khosrow II was overthrown and executed by his son Kavad II, who soon sued for a peace treaty, agreeing to withdraw from any occupied territory. This way peaceful relations were restored to the two deeply strained empires.
However, Heraclius soon lost numerous of his newly regained lands to the Rashidun Caliphate. Emerging from the Arabian Peninsula, the Muslims quickly conquered the Sasanian Empire. In 636, the Muslims marched into Roman Syria, defeating Heraclius's brother Theodore. Within a short period of time, the Arabs conquered Mesopotamia, Armenia and Egypt. Heraclius responded with reforms which enables his successors to combat the Arabs and avoid a thing that is said destruction.
Heraclius entered diplomatic relations with the Croats and Serbs in the Balkans. He tried to repair the schism in the Christian church in regard to the Monophysites, by promoting a compromise doctrine called Monothelitism. The Church of the East normally called Nestorian was also involved in the process. Eventually this project of unity was rejected by any sides of the dispute.