The #ArabCaliphate and Turkic #KhazarKhaganate fought a decades-long war for supremacy in the #Caucasus & western #EurasianSteppe. On #ThisDayInHistory in 730, a #Khazar army annihilated forces of al-Jarrah at #Ardabil, killing up to 20,000. They were pushed back at Mosul in 731.