The Battle of Ongal (680)

Asparuh, son of Kubrat Khan, led part of the Bulgars west and settled in the Danube delta, in a marshy area called Ongal, from where he raided Byzantine lands. In 680 the emperor Constantine IV, having made peace with the Arabs, marched against the Bulgars with a large army and fleet.

The Bulgars first withdrew to their fortifications among the marshes of Ongal. According to the chronicle of Patriarch Nikephoros, the emperor left for Mesembria to treat a painful foot. A rumour spread through the army that he had fled, and the Byzantine troops began to fall back in confusion.

Asparuh seized the moment, came out of his fortifications, pursued the retreating army and dealt it a heavy defeat. The Bulgars crossed the Danube, and in 681 Byzantium made a peace that recognised the Bulgar state south of the Danube and agreed to pay it yearly tribute.