On 8 July 1167 a Byzantine army under Andronikos Kontostephanos destroyed the Hungarian army near Sirmium, forcing Hungary to accept Byzantine overlordship. Manuel I, to whom the victory is usually credited, was not there.
The Battle of Sirmium was fought on 8 July 1167 on the lower Sava, and it settled a decade of Byzantine intervention in the affairs of the kingdom of Hungary.
The Byzantine army destroyed the Hungarian one, and Hungary accepted Byzantine overlordship along with the loss of Syrmia, Bosnia and Dalmatia. It is the furthest imperial authority reached in Europe after the eleventh century.
It is also routinely credited to the wrong man. **Manuel I Komnenos was not present at the battle**; the army was commanded by his nephew Andronikos Kontostephanos, the megas doux, and the plan and the execution were his.
Manuel I spent his reign trying to make the Balkans a Byzantine sphere, and Hungary was the largest obstacle and the largest opportunity. From the 1150s he intervened repeatedly in Hungarian succession disputes, backing claimants and taking hostages.
The most ambitious version of the policy was dynastic: Manuel brought the Hungarian prince Béla to Constantinople, betrothed him to his daughter, gave him the invented title of despot, and for a time intended him as heir to the empire — which would have united the two crowns.
When Manuel's own son was born in 1169 that plan lapsed, but in 1167 it was still live, and the war was fought over exactly that: whether Hungary would be a Byzantine client or an independent kingdom.
Kontostephanos brought the army to the Sava in the summer of 1167 and met the Hungarian force, commanded by a general the Byzantine sources call Dénes, near Sirmium.
He arranged his line with the heaviest cavalry in the centre and archers and light troops on the flanks, and received the Hungarian charge rather than meeting it — a deliberate choice, and the sources make clear it was his.
The charge broke on the Byzantine centre, the flanks closed, and the Hungarian army was destroyed. The Byzantine accounts describe enormous quantities of captured armour and standards, and Kontostephanos sent the news to the emperor in Constantinople.
This archive states the correction plainly because the error is so common. Manuel I was in Constantinople. The campaign was planned in his name and the credit was taken in his name, and John Kinnamos and Niketas Choniates both make clear that Andronikos Kontostephanos commanded on the day.
Kontostephanos was Manuel's nephew, held the office of megas doux, and had already commanded in Italy and at sea. Sirmium is his victory and it is the one usually filed under the emperor's name.
He has no article in this archive for the ordinary reason: no image of him survives in any form. He is named here as the commander, with the correction stated, which is the best the archive's rules allow.
Hungary came to terms. Byzantine overlordship was acknowledged, Syrmia and the Dalmatian coast passed to the empire, and Bosnia came into the imperial sphere. Manuel celebrated a triumph in Constantinople.
The settlement held for thirteen years and did not survive him. Béla returned to Hungary in 1172 as king Béla III — a Byzantine-raised monarch who was, in the end, a Hungarian one — and after Manuel died in 1180 the ceded territories went back.
The Komnenian position in Europe unravelled quickly afterwards, and the empire never again held the Sava.
Sirmium is the high-water mark of the twelfth-century recovery in Europe, as Antioch was in the east two centuries earlier. For a decade the empire held a frontier on the Danube and the Sava and a client kingdom beyond it.
The speed of the collapse after 1180 is the standing lesson of the Komnenian period: the system depended on one capable emperor, and the machinery of client states and dynastic marriages he built did not outlive him by three years.
The battle also stands as this archive's clearest case of misattributed credit — not propaganda, as with Michael III, but the ordinary process by which a reign absorbs the achievements of the people who served it.