Waves of Huns, Goths, Visigoths, and Ostrogoths invaded and plundered the Balkans beginning in the third century A.D. None of these invaders permanently occupied territory. Small Slavic groups began settling outlying regions in the fifth century, and by the seventh century the Slavs had overcome Byzantine resistance and settled most of the Balkans. The Slavs brought a more stable culture, retained their own language, and substantially slavicized the existing Roman and Byzantine social system.

The immigration of the first Bulgars overlapped that of the Slavs in the seventh century. Of mixed Turkic stock (the word Bulgar derives from an Old Turkic word meaning "one of mixed nationality"), the Bulgars were warriors who had migrated from a region between the Urals and the Volga to the steppes north of the Caspian Sea, then across the Danube into the Balkans. Besides a formidable reputation as military horsemen, the Bulgars had a strong political organization based on their khan (prince). In A.D. 630 a federation of Bulgar tribes already existed in the next years the Bulgars united with the Slavs to oppose Byzantine control. By 681 the khan Asparukh had forced Emperor Constantine V to recognize the first Bulgarian state. The state, whose capital was at Pliska, near modern Shumen, combined a Bulgarian political structure with Slavic linguistic and cultural institutions.

Data as of June 1992