
Defeated the Sassanid Persians, lost the Levant to Muslim conquest.
Compare Heraclius with another historical figure:
Heraclius led a revolt from Carthage against the usurper Emperor Phocas. He sailed to Constantinople, where supporters opened the gates. Phocas was captured and executed, and Heraclius was crowned emperor, ending a period of civil strife and military decline.
Heraclius personally led a multi-year campaign against the Sassanid Persian Empire, which had occupied much of Byzantine territory. He defeated Persian forces at the Battle of Nineveh in 627 and recovered the True Cross, restoring Byzantine prestige and ending the war.
Heraclius's forces were decisively defeated by the Rashidun Caliphate at the Battle of Yarmouk. This loss led to the permanent loss of Syria, Palestine, and Egypt to Muslim rule, drastically reducing Byzantine territory and marking the beginning of the Arab-Byzantine wars.
See how Heraclius stacks up against other historical figures