Bulgars

The Bulgars (also Bolgars or proto-Bulgarians) were a seminomadic people, probably of Turkic descent, originally from Central Asia, who from the 2nd century onwards dwelled in the steppes north of the Caucasus and around the banks of Volga (then Itil). A branch of them gave rise to the First Bulgarian Empire.

Bulgars in "Islands in the Sea"
In AD 769, the Bulgar Khan Telerikh decided to convert his entire people to Islam.