The marriage of John Komnenos to the Hungarian princess Piroska has involved him in the dynastic struggles of the Kingdom of Hungary.
In giving asylum to Álmos, a blinded claimant to the Hungarian throne, John had aroused the suspicion of the Hungarians, who, led by Stephen II, had invaded the Empire’s Balkan provinces in 1127, with hostilities lasting until 1129 (however, an alternative chronology has been suggested with the Hungarian attack and Greek retaliation taking place in 1125 with a renewal of hostilities in 1126).
The Hungarians had attacked Belgrade, Niš, and Sofia; John, who was near Philippopolis in Thrace, counterattacked, supported by a naval flotilla operating on the River Danube.
After a challenging campaign, the details of which are obscure, the emperor manages to defeat the Hungarians and their Serbian allies at the fortress of Haram or Chramon, which is the modern Nova Palanka; many Hungarian troops are killed when a bridge they are crossing collapses as they are fleeing from an attack by imperial forces.
John then launches a punitive raid against the Serbs, who had aligned themselves with Hungary, many of whom are rounded up and transported to Nicomedia in Asia Minor to serve as military colonists.
This wis done partly to cow the Serbs into submission (Serbia was, at least nominally, an imperial protectorate, and partly to strengthen Constantinople’s frontier in the east against the Turks.
The Serbs are forced to acknowledge imperial suzerainty once again.
The Serbian campaign may have taken place between two distinct phases in the war against Hungary.
