The Kutrigurs (Kotrags/Kotzagerek/Kazarig), first mentioned in 539/540, were a horde of equestrian nomads later known as part of the Bulgars that inhabited the Eurasian plains during the Dark Ages. They came into existence when the Eurasian Avars conquered half of the Hunno-Bulgars, whilst the remaining group, who were free (led by Sandilch in the east) were called Utigurs. The conquest of the easternmost Kutrigurs by Gokturk arrivals led by three brothers from the Imaon Mountains in the 6th century is mentioned by Bar Hebraeus, as well as in the Chronicle of the late 12th century Jacobite patriarch of Antioch Michael the Syrian[1]. At this time they came to be dominated by clans related to the Göktürks.
In 632, Kubrat united the Kutrigur and Utigur tribes who lived in Scythia. Upon their unification, the state which East Roman scholars referred to as Old Great Bulgaria was established.
When the Khazar state expanded, it challenged the dominance of Old Great Bulgaria. The Khazars were able to obtain tribute from Batbayan, Kubrat's eldest son, and so came the downfall of Great Bulgaria. In the mid 7th century, a dissenting faction of Kutrigurs seems to have traveled to the upper Volga where, along with part of the Utigurs, they founded the state of Volga Bulgaria with Kotrag as its ruler.
Under the leadership of Kuber, another part of the Kutrigur tribe seems to have moved to Sirmium (Pannonia) and from there south to the Pelagonian plain. Thereafter they disappear from history as a separate Bulgar group. Kuber's Kutrigur Bulgars displaced some of the populations that had already settled in the region of Macedonia, and intermingled with the populations that remained. In the 8th century, the Kuber Bulgars merged with Asparuh's Bulgars who had already settled on both sides of the Danube River in the late 7th century.