The dynasty that ruled the eastern Roman empire from 610 to 711, destroyed Persia, lost the east to the Arab conquests, and turned a Latin empire into a Greek one.
The dynasty came to power by revolt from the far edge of the empire. Heraclius the Elder was exarch of Africa, governing from Carthage, and in 608 he rebelled against the emperor Phocas, who had seized the throne in 602 by murdering Maurice and had since presided over military collapse.
His son sailed for Constantinople and deposed Phocas in 610. The family was of Armenian descent and had made its career in the provincial military aristocracy rather than at court, which is a pattern that recurs through Byzantine history: the capital changes dynasty when a frontier general decides it should.
What Heraclius inherited was a war he was losing. Persia held Syria and Palestine, Jerusalem fell in 614, and Egypt — the grain supply — was gone by 619.
From 622 Heraclius campaigned in person for six years, striking into Armenia and the Persian heartland instead of defending the lost provinces. In 626 the capital held against a combined Avar and Persian siege while he was away in the east, and in December 627 he destroyed the Persian field army at Nineveh.
Khosrow II was deposed and executed within two months, the conquered provinces were returned, and the True Cross went back to Jerusalem in 630. It was the most complete victory the empire had won in centuries.
It was also the most expensive. Both empires had spent a generation and their treasuries on the war, and both were left too weak to resist what came next.
Arab armies entered Syria in the mid-630s and the empire could not hold them. Syria, Palestine and Egypt were lost within a decade, and by the reign of Constans II the frontier had settled on the Taurus mountains, where it stayed for three hundred years.
Constans II responded by moving west, taking his court to Syracuse in Sicily in 663 — a decision that looks like abandonment from Constantinople and like strategy from the Mediterranean, and which ended with his murder in his bath in 668.
The dynasty's greatest defensive achievement came under his son. Constantine IV held Constantinople through the first sustained Arab attempt on the city between 674 and 678, and the campaign saw the first recorded use of Greek fire — the weapon that would save the city again in 717.
Justinian II took the throne in 685 at sixteen and lost it in 695, when he was deposed, had his nose slit — a mutilation intended to disqualify him permanently — and was exiled to the Crimea.
He came back. In 705 he retook Constantinople with Bulgar help and reigned a second time, wearing a gold nose, and spent six years pursuing the people who had deposed him.
He was killed in 711 and his young son with him, ending the line. The empire then went through six emperors in six years, until a provincial general named Leo took the throne in 717 with an Umayyad army already marching on the capital.
The Heraclians presided over the transformation that separates the eastern Roman empire from Byzantium as historians usually mean it. Greek replaced Latin as the language of state, the imperial title changed from Augustus to Basileus, and the provincial system began to be reorganised into the themes that would defend Anatolia for centuries.
The territorial record is brutal: the dynasty inherited an empire holding Syria, Palestine, Egypt and North Africa and left one that held none of them. What it did leave was a state that had survived losing them, which no contemporary would have predicted in 640.
Greek fire, the themes, and a capital that had learned it could be held against anything are the three inheritances the Isaurians used to stop the Arab conquests at the walls in 718.