Petronas was the Byzantine general who destroyed the army of the emir of Melitene at the Lalakaon in 863, the victory that turned the eastern frontier in the empire's favour.
Petronas belonged to the family that ran the empire in the middle of the ninth century: brother of the empress Theodora, brother of Bardas who governed as Caesar, and uncle of the emperor Michael III.
He held military command through the 850s and 860s, including the office of Domestic of the Schools, which put the central regiments of the army under him. His career is otherwise sparsely recorded, as most Byzantine generals' are.
In September 863 he destroyed the raiding army of Umar al-Aqta, emir of Melitene, at the river Lalakaon in Paphlagonia. It is the reason he has an article, and the reason the tenth-century reconquest of the east was possible.
His birth is not recorded and neither is his year of birth; the family came from Paphlagonia in northern Anatolia and rose with his sister's marriage to the emperor Theophilos.
When Theophilos died in 842, Theodora became regent for the child Michael III, and her brothers moved into the centre of government. Petronas took military office and his brother Bardas took politics.
In 856 the brothers removed Theodora and her minister Theoktistos and put the sixteen-year-old Michael in nominal charge with Bardas as the real ruler. Petronas's part in that coup is recorded without detail, which is typical of what the sources preserve about him.
Very little survives of him as a person, and honesty requires saying so rather than assembling a character from a single battle.
What the chronicles do preserve is a reputation for competence rather than for the qualities they usually praise. He is not described as pious, or eloquent, or generous; he is described as the man who was given the eastern command in a bad year and produced the one result nobody had managed in two centuries.
The one personal story the tradition tells is the meeting with John, the monk of Latros, who is said to have foretold his victory — the scene the Skylitzes manuscript illustrates. It says more about how chroniclers explained success than about Petronas, and it is included here as what it is: a story attached to a winner.
In 863 Umar al-Aqta led his army from Melitene across Anatolia to Amisos on the Black Sea. Petronas was given the response, and did not attempt to meet the raiders head-on.
Instead he assembled forces from the western themes, the eastern themes and the Black Sea coast and moved them so that they converged on the returning column, closing around it in the valley of the Lalakaon and taking the high ground before the fighting began.
The encirclement held. The raiding army was destroyed on 3 September and the emir was killed attempting to break out. The manoeuvre required several separate commands to arrive in the right places at once, which is the part of it that deserves the credit.
He was raised to the rank of magistros, one of the highest dignities of the court, and a triumph was celebrated in Constantinople for the victory.
He died two years later, in 865, before the crisis that destroyed the rest of his family: his brother Bardas was murdered in 866 and his nephew Michael in 867, both at the hands of Basil the Macedonian.
His reputation survived that change of dynasty intact, which is unusual for anyone associated with Michael III. The Macedonian historians who blackened the emperor had no reason to diminish the general, and the victory was too useful to the empire's self-image to be spoiled.
The Lalakaon is the hinge of the Arab–Byzantine wars, and Petronas is the man who planned it. After 863 the frontier emirates were no longer able to mount the annual invasions that had defined the border for two centuries, and the empire began to push east.
The campaigns that took Melitene in 934, and Cilicia, Antioch and Aleppo in the decades after, followed the opening he made. He did not live to see any of it.
He is a good example of a figure this archive exists to keep visible: a commander with one securely recorded achievement of the first importance, whose life is otherwise almost entirely unrecoverable.