In 740 Leo III and his son Constantine destroyed an Umayyad raiding army at Akroinon in Phrygia, killing both its commanders. It was the last great Umayyad invasion of Anatolia.
In 740 an Umayyad army crossed into Anatolia in three divisions, as it had done nearly every year for a century. One of them, some twenty thousand strong under Abdallah al-Battal and Malik ibn Shu'ayb, was met at Akroinon in Phrygia by a Byzantine army under the emperor Leo III and his son Constantine.
The division was destroyed and both commanders were killed. That is the whole of the engagement, and its importance is entirely in what it ended rather than in how it was fought.
The raids had been the empire's permanent condition since the 660s. Akroinon was the last of the great ones, and within ten years the dynasty that had launched them no longer existed.
The failure at Constantinople in 717–718 had cost the caliphate a fleet and an army but not the initiative. Umayyad forces continued to cross the Taurus passes almost every year, sacking towns, taking captives and occasionally wintering on Byzantine soil.
Leo III had spent the intervening two decades on the answer: the theme system, which settled soldiers on land they had reason to defend and put a standing provincial army where the raiders would arrive. The empire could not stop the raids at the frontier, but it could increasingly punish them on the way home.
The 740 campaign was launched under the caliph Hisham and was large even by the standards of the period. Its three divisions ranged separately, which is what allowed the Byzantines to engage one of them alone.
The Byzantine army caught the division under al-Battal and Malik ibn Shu'ayb at Akroinon, in Phrygia, well inside Anatolia. Theophanes puts the raiding force at twenty thousand and its dead at over thirteen thousand, and the figures should be read as an order of magnitude rather than a count.
What the sources agree on is the completeness of it: the division broke, both of its commanders were killed, and the remnant escaped to Synnada in poor order. Byzantine armies had beaten raiding parties before; destroying a full division with its leadership was new.
The reader should note the name of the losing commander. Abdallah al-Battal was already a celebrated frontier warrior, and after his death he grew into Battal Gazi, the hero of a Turkish and Islamic epic tradition that outlived every state involved — a shrine at Seyitgazi still marks the tomb associated with him. The man who lost the battle is far better remembered than the emperor who won it.
The Umayyad caliphate was already straining, and in 750 it was overthrown by the Abbasid revolution and the capital moved from Damascus towards Iraq. The new dynasty continued the raids, but from a court a thousand miles further east and with its attention on Khurasan, Iran and its own succession.
For the empire the change was decisive without being visible at once. The frontier stayed violent for two more centuries, but the annual campaign to destroy the Roman state stopped, and Constantinople was never besieged by a caliphal army again.
Leo III died in 741 and the throne passed to Constantine V, who had fought here as a young man and who spent his reign on the offensive — against the Bulgars in the Balkans and across the Taurus into Syria.
Akroinon is a small battle with a large position in the story. It closes the century of Umayyad offensives that had begun with the conquest of Syria and had twice reached the walls of Constantinople.
It is also the point where the theme system can first be seen working as designed: a provincial army raised where the enemy would come, commanded by an emperor who had been a provincial general himself, catching a raiding column that had grown used to being unopposed.
The eastern balance did not tip here — that took another century and a quarter, and the battle at the Lalakaon in 863. But this is where it stopped tipping the other way.
Theophanes the Confessor supplies the Byzantine account, with the numbers, and the Arabic tradition records the campaign and the death of al-Battal without dwelling on the defeat.
The two traditions can be checked against each other on this occasion, and they agree that the division was destroyed and its commanders killed. They disagree on scale, as they always do.
The largest distortion is not in either chronicle but in what came afterwards: al-Battal's epic afterlife means much of what is popularly said about Akroinon is drawn from a legendary cycle composed centuries later, in which he is not defeated at all.