After his accession, Telets led a well-trained and well-armed army against the Byzantine Empire and devastated the Empire's frontier zone, inviting the emperor to a contest of strength.

Emperor Constantine V Kopronymos marched north on June 16, 763, while another army was carried by a fleet of 800 ships (each carrying infantry and 12 horsemen) with the intent to create a pincer movement from the north.

The energetic Bulgarian Khan at first barred the mountain passes with his troops and some twenty thousand Slavic auxiliaries and took advantageous positions on the heights near Anchialus, but his self-confidence and impatience incited him to go down to the lowlands and charge the enemy. The battle started at 10 in the morning and lasted until sunset. It was long and bloody, but in the end the Byzantines were victorious, although they lost many soldiers, nobles, and commanders. The Bulgarians also had heavy casualties and many were captured, while Telets managed to escape. Constantine V entered his capital in triumph and then killed the prisoners. The fate of Telets was similar: two years later he was murdered because of the defeat.