Dulo clan
Subsequent events proved Old Great Bulgaria to be only a loose tribal union, as there emerged a rivalry between the Khazars and the Bulgars over Turk patrimony and dominance in the Pontic–Caspian steppe. Some historians consider the war an extension of the Western Turks struggle, between the "Nushibi" tribes and Ashina clan, who led the Khazars, and the "Duolu/Tu-lu" tribes, which some scholars associated with the Dulo clan, from which Kubrat and many Bulgar rulers originated. The Khazars were ultimately victorious and parts of the Bulgar union broke up.