Like today many centuries ago, on June 30, 763 AD. a hugely important battle was fought that is largely acknowledged by historians but nevertheless saved the Byzantine Empire and dismantled the danger from the North for a long time. In the late spring of AD 763 the Bulgarian tsar Tellets invaded Byzantine lands in Thrace, burning and looting.
On hearing the news, the emperor Constantine V Isauros, gathered the imperial battalions and from Constantinople, moved to meet the raiders, with the help of the fleet, in whose ships the army was being transported, in order to gain time, but also to managed to find himself, if this was possible, in the back of the opponent.
The Bulgarians, however, were informed of the emperor's movements and retreated to the mountains, northwest of the city of Anchialos, guarding all the mountain passes. Nevertheless, the vanity of the Bulgarian tsar made him leave his strong positions and risk fighting on the plain outside Aghialos with Constantine. Apparently, he had also been reinforced with parts of his Slavic infantry subjects.
The battle that took place was particularly long and bloody. It started around 10.00 in the morning and ended after almost 10 hours. Byzantines and Bulgarians fought fiercely, but in the end Telec's army was crushed and he barely managed to escape, unlike most of his officials who were either killed or captured. Constantine was the first to receive the title of Bulgarian Slayer.