Khan Asparukh (681-701) succeeded in stopping Khazars' offensive but kept only a small part of the Old Great Bulgaria between the rivers Dnepr and Danube - land infertile and marshy, short of natural shelters. That is why he decided to undertake a territorial expansion campaign at the fruitful lands of the ancient Moesia - the area between the Danube River and the Balkan Mountains.

In 680 khan Asparukh at the head of a significant part of the Bulgarian army crossed the Danube and passed over the whole Moesia. After that the Bulgarian troops devastated Thrace - the area on the south of the Balkan and came back with many spoils. Essentially, these  actions were equivalent to declaring war on the Byzantine empire. The Roman emperor Constantine IV Pagonatus prepared a large army of infantry and cavalry, a vast assortment of siege equipment, a formidable naval forces and set off to the Danube. The decisive battle occurred at the Danube delta area at the end of the summer. The Bulgarian troops utterly routed the Roman legions.

The next year khan Asparukh concluded with the seven Slav tribes living in Moesia treaty under which the Slavs recognized their dependence on the Bulgarian state and committed itself to defend it against attacks by any enemy. The alliance combined the large but sluggish and undisciplined infantry troops of the Slav tribes with the fast, hard-hitting and well-organized Bulgarian cavalry.

The united Slav-Bulgarian forces crossed again the Balkan and struck a series of stunning blows on the Byzantine troops. In the autumn of 681 Byzantium was forced to conclude a peace treaty with the Bulgarians and recognized the detachment of Moesia from the empire. This was the official recognition of a new political reality - the Bulgarian state on the Balkan Peninsula.

So the year 681 is the Year One of Bulgaria's history.