. "returned to Bulgaria" . . "then moving on" . "Mongol attacks" . . . . . "Conquered" . "Unknown, defeated in their first attack" . . . . . . . . . . . . "Mongol invasions of Volga Bulgaria" . . "Mongol Empire" . . . . "1236: ~35,000" . . . "Mongol invasion of Volga Bulgaria" . . "Invasion of Volga Bulgaria" . "1223\u20131236 invasion of Volga Bulgaria" . . "defeated major Volga Bulgarian" . "Mongols ravaged the Bol\u011Far and Bil\u00E4r territories" . . "Volga Bulgaria" . "Batu Khan invasions" . "Initial raids repulsed, subsequent invasions were a decisive Mongol victory" . "Mongol invasion of Volga Bulgaria" . "invaded Volga Bulgaria" . "1223: Less than 20,000" . "Mongol invasion" . . "Volga Bulgaria" . "1229: 20,000" .