The year 681 is accepted as Year One of Bulgaria's history.

The formation of the state was not the result of a single act. The western chronicler Siegebert added to his notes on the year 680: 'Henceforth the Bulgarian kingdom must be noted'. This statement was fully justified, for Khan Asparouh's Bulgaro-Turks had united with the Seven Slav tribes who inhabited the territory north of the Balkan Range from as early as the first battles with Byzantium. The Byzantine chroniclers Patriarch Nicephorus (8th century) and Theophanes the Confessor (late 8th and early 9th century) gave a more detailed account of the occurrences of the time. To quote Theophanes on the treaty of the Byzantine empire with the new state, forced by the actions of the Proto-Bulgarians, 'the emperor made peace with them, undertaking to pay an annual tax to the disgrace of the Byzantines and because of our numerous sins. It is a wonder for all people, both far and near, to hear that the man who had made all people to the East, West, North and South pay taxes to him, was defeated by this new people'.

Among domestic sources on the foundation of the Bulgarian state the most important is the Book of the Bulgarian Khans - the first Bulgarian chronicle, compiled at two different times: initially during the rule of the founder of the Bulgarian state Khan Asparouh (680-701), and during the second half of the eighth century.

The new Bulgarian state united Proto-Bulgarians, Slavs and the native population, which consisted mainly of Thracians. Its borders in the centuries that followed varied between the Black Sea, the Aegean and the Adriatic Sea. Included into its border for a long time were the central and northeastern parts of the Balkan Peninsula where traces of human life have been found from the end of the early paleolithic period, dating 200,000 years. A centre of civilization, considered to be the earliest in Europe and comparable to ancient Egypt and Mesopotamia, has been found in this region and mainly in the plains to the north and south of the Balkan Range during archaeological excavations. It has been established that the people who lived in the farming communities of the Early and New Stone Age were familiar with metal casting and applied it independently of other early civilizations.