Dulo clan
At this period the area divided from the Jireček Line was populated from people of Thraco-Roman or Illyro-Roman origins, as well from Hellenized citizens of the Byzantine Empire and Byzantine Greeks. The ancient languages of the local Thraco-Illyrian people had already gone extinct before the arrival of the Slavs, and their cultural influence was highly reduced due to the repeated barbaric invasions on the Balkans during the early Middle Ages, accompanied by persistent hellenization, romanisation and later slavicisation. South Slavic tribes settled in the territory of present-day North Macedonia in the 6th century. The Slavic settlements were referred to by Byzantine Greek historians as "Sklavinies". The Sklavinies participated in several assaults against the Byzantine Empire - alone or aided by Bulgars or Avars. Around 680 AD the Bulgar group, led by khan Kuber (who belonged to the same Dulo clan as the Danubian Bulgarian khan Asparukh), settled in the Pelagonian plain, and launched campaigns to the region of Thessaloniki.