In 721/2, the main phase of the
Second Arab–Khazar War began on the
Caucasus front. In the winter of this year, 30,000 Khazars launched an invasion of
Armenia and inflicted a crushing defeat on the army of the local governor Mi'laq ibn Saffar al-Bahrani at Marj al-Hijara in February/March 722. In response, Caliph
Yazid II (r. 720–724) sent al-Jarrah with 25,000
Syrian troops to Armenia, placing him in command of the Umayyad offensive against the Khazars. Al-Jarrah was swiftly successful in driving the Khazars back across the Caucasus, and fought his way north along the western coast of the
Caspian Sea, recovering
Derbent and advancing onto the Khazar capital of
Balanjar. The Khazars
tried to defend the city by ringing the citadel with a
laager of wagons, but the Arabs broke it apart and stormed the city on 21 August 722 (or 723). Most of Balanjar's inhabitants were killed or enslaved, but a few managed to flee north. The Arabs also took the town of
Wabandar, and even approached
Samandar (near modern
Kizlyar). Despite these successes, the Arabs could not achieve a decisive result. The main Khazar army remained intact and a constant threat, since like all nomad forces it was not dependent on cities for supplies. Coupled with the fact that his rear was still insecure, al-Jarrah was forced to abandon any attempt at capturing Samandar as well, and to retreat to
Warthan south of the Caucasus. From there he asked for reinforcements from Yazid, but although the Caliph promised to send more troops, he failed to do so. The sources are obscure on al-Jarrah's activity in 723, but he seems to have led another campaign north (which may indeed be the true date of the Balanjar campaign). In response, the Khazars raided south of the Caucasus, but in February 724, al-Jarrah inflicted a crushing defeat on them in a battle between the rivers
Cyrus and
Araxes that lasted for several days. Al-Jarrah followed up his success by capturing
Tiflis, whose inhabitants were obliged to pay the
kharaj but received a charter of rights in return. This campaign brought
Caucasian Iberia and the lands of the
Alans under Muslim suzerainty, and al-Jarrah became the first Muslim commander to march through the
Darial Pass in the process. This expedition secured the Muslims' own flank against a possible Khazar attack through the Darial, while conversely it gave the Muslim army a second invasion route into Khazar territory. In 725, however, the new Caliph
Hisham ibn Abd al-Malik (r. 724–743) replaced al-Jarrah with his own brother Maslamah ibn Abd al-Malik. ==Recall to the Caucasus and death==