In 721/722, the main phase of the war began. In the winter of this year, 30,000 Khazars invaded Armenia and inflicted a crushing defeat on the mostly Syrian army of the local governor Mi'laq ibn Saffar al-Bahrani at Marj al-Hijara in February and March 722. In response, Caliph Yazid II () sent one of his most celebrated generals, al-Jarrah ibn Abdallah, with 25,000 Syrian troops north. On the news of his approach, the Khazars retreated to the vicinity of Derbent, whose Muslim garrison was still holding out. Advancing swiftly, al-Jarrah was able to enter Derbent without facing resistance, and launched raiding columns into Khazar territory. Following with the bulk of his own army, he defeated a 40,000-strong Khazar army under Barjik, one of the Khazar "khagan"s sons, one day's march north of Derbent. Advancing north, the Arab army captured the settlements of Khamzin and Targhu, whose inhabitants were resettled elsewhere. Finally, the Arab army reached Balanjar. The city had featured strong fortifications during the first Muslim attacks in the mid-7th century, but apparently they had been neglected in the meantime, for the Khazars chose to defend their capital by ringing the citadel with a laager of wagons. The Arabs broke it apart and stormed the city on 21 August 722. Most of Balanjar's inhabitants were killed or enslaved, but a few, including its governor, managed to flee north. The booty seized by the Arabs was so enormous that each of the 30,000 horsemen—probably an exaggeration by later historians—in the Arab army is said to have received 300 gold dinars from it.