In 1223, after defeating Russian and Cuman/Kipchak armies at the Battle of Kalka, a Mongol army under the generals Subutai and Jebe was sent to subdue Volga Bulgaria. Genghis Khan's troops were seen as invincible at that time. However, in late 1223 (or 1224), the Bulgars may have fought with the Mongols. There is no historical mention except a short account by the Arab historian Ibn al-Athir, writing in Mosul some away from the event. After several sharp skirmishes with the Bulgars, the tiring Mongols moved back down to the Volga. Meanwhile, the Russians continuously attacked the Bulgar State to try to attain supremacy of this wealthy region.