Heraclius ruled the eastern empire from 610 to 641, took it to the brink of destruction and back, defeated Persia — and then lost everything he had won to the Arab conquests.
Heraclius came to the throne in 610 by overthrowing a usurper, and inherited an empire that was in the process of losing.
Persia held Syria, Palestine and Egypt; the Avars were in the Balkans; Jerusalem had fallen and the True Cross had been carried off. In 626 Constantinople itself was besieged from both sides at once.
He then did something no emperor had done for centuries: he took the field in person for six years and won the war outright. And within a decade of that victory, the Arab conquests took the east away permanently.
He was born around 575 into a family of Armenian descent, the son of the exarch of Africa, and grew up in the provincial military aristocracy rather than at court.
In 608 his father revolted against the emperor Phocas, who had seized power in 602 by murdering Maurice, and the revolt was run from Carthage.
Heraclius sailed to Constantinople in 610, deposed Phocas and had him executed. He inherited the war Phocas had provoked and no obvious means of fighting it.
The sources are thinner and more partisan than for Justinian, and much of what survives is panegyric — George of Pisidia wrote verse in his praise while the campaigns were still running, and later Byzantine writers treated him as a model Christian emperor.
What the record consistently shows is personal courage and an unusual willingness to campaign in person, which had not been normal imperial behaviour for two hundred years. He is described leading from the front and, at Nineveh, killing the Persian commander in single combat.
The later years read very differently. Illness, a marriage to his niece Martina that scandalised the church, dynastic anxiety, and then the Arab conquests undoing everything — the sources describe an old man who would not cross the Bosphorus by ship and had a bridge of boats disguised with branches. Whether that is illness, terror or invention is not recoverable.
The first decade was disaster. Antioch, Damascus and Jerusalem fell, the True Cross was taken to Ctesiphon, and by 619 Egypt — the empire's grain supply — was Persian.
From 622 Heraclius campaigned in person, striking into Armenia and the Persian heartland rather than defending the lost provinces directly, and funding the war partly on the treasure of the church.
In 626 Constantinople was besieged by the Avars from Europe and the Persians from Asia while he was away in the east. The walls and the fleet held, and the failure broke the coalition.
In December 627 he brought the Persian field army to battle near the ruins of Nineveh and destroyed it, then marched on the royal residence at Dastagird.
Khosrow II was overthrown by his own nobles and son in 628 and executed, and the peace that followed restored the pre-war frontier and the True Cross, which Heraclius returned to Jerusalem in 630.
It was, on paper, the most complete victory the empire had won in centuries.
It lasted about six years. Arab forces entered Syria from the mid-630s, and the empire — exhausted, its provinces devastated by twenty years of Persian occupation and reconquest — could not hold them.
Syria was lost, then Palestine, then Egypt. Heraclius took the True Cross from Jerusalem back to Constantinople rather than see it captured again, and died in 641 with the eastern provinces gone.
The empire that survived him was a different thing: smaller, Greek rather than Latin in its administration, and permanently defensive. He changed the imperial title from Augustus to Basileus, which is a fair marker of the transition.