In 729/730, al-Jarrah returned to the offensive through Tiflis and the Darial Pass. Arab sources report that he reached as far as the Khazar capital, al-Bayda, on the Volga, but modern historians such as Dunlop and Blankinship consider this improbable. The Khazars launched a counterstroke under a certain Tharmach, which forced al-Jarrah to retreat south of the Caucasus once again to defend Albania. It is unclear whether the Khazars came through the Darial Pass or the Caspian Gates, but they managed to move around al-Jarrah's army at Bardha'a and lay siege to Ardabil. The city was the capital of Adharbayjan, and the mass of the Muslim settlers and their families, some 30,000 in total, lived within its walls. When al-Jarrah learned of this, he led his army in a rapid march south and engaged the Khazars outside the city walls. There, after a three-day battle on 7–9 December 730, al-Jarrah's army of 25,000 was all but annihilated by the Khazars under Barjik. Al-Jarrah was among the fallen, and command passed to his brother al-Hajjaj, who was unable to prevent the sacking of Ardabil. The 10th-century historian Agapius of Hierapolis reports that the Khazars took as many as 40,000 prisoners from the city, al-Jarrah's army, and the surrounding countryside. The Khazars raided the province at will, sacking Ganza and attacking other settlements, with some detachments reaching as far as Mosul in the northern Jazira, adjacent to the Umayyad metropolitan province of Syria.