Page "History of Russia" Paragraph 24

After the fall of the Khazars in the 10th century, the middle Volga came to be dominated by the mercantile state of Volga Bulgaria, the last vestige of Greater Bulgaria centered at Phanagoria.

In the 10th century the Turkic population of Volga Bulgaria converted to Islam, which facilitated its trade with the Middle East and Central Asia.

In the wake of the Mongol invasions of the 1230s, Volga Bulgaria was absorbed by the Golden Horde and its population evolved into the modern Chuvashes and Kazan Tatars.