In 721 the Khazars took the offensive, invading Armenia and destroying Muslim garrisons. This was followed by 15 years of warfare, during which the Caliphate’s still largely Arab forces were often greatly outnumbered but generally more sophisticated. They were superior in technology, tactics, and political strategy (for example, attempting to win over local inhabitants while expelling Khazar garrisons). On one occasion the Muslim commander Jarrah ibn Abdallah took Samandar, then turned south again towards Balanjar. In an attempt to bar his passage the Khazar garrison used an old form of field fortification long traditional amongst steppe nomads, constructing a camp surrounded by wagons and carts tied together. However, Muslim soldiers advanced to this perimeter under the cover of arrows (probably shot by Arab infantry), cut the ropes and broke through the Khazars’ barrier. After brutal hand-to-hand combat, the ‘prince’ (governor) of Balanjar and 50 of his men escaped, while leaving the Khazar leader’s family to be captured. Jarrah ibn Abdallah now sent another senior captive after the Khazar commander, promising that he could continue ruling Balanjar under Muslim suzerainty. Following this successful campaign, in which both Balanjar and Samandar cities were left intact in return for payment of tribute, each Arab cavalryman was rewarded with 300 dinars from the booty, while infantrymen got 100 each; one-fifth of the total loot was also set aside for the caliph’s government. Jarrah wanted to continue the campaign but, with cold weather approaching, and having been warned that another Khazar army was assembling, he took his troops back to winter quarters in Azerbaijan. As so often happened in this part of the world, ‘General Winter’ had intervened to force back an invader.
In 730, encouraged by recent successes, the Khazars invaded Islamic territory. They were commanded by Barjik, whom Arab chroniclers described as ‘son of the Khagan’, though he may already have been the ruler. Bursting into Azerbaijan, he ordered his troops to slaughter Muslims wherever they were found, and led the main Khazar force towards Ardebil. Here, outside the city walls, the veteran Jarrah ibn Abdallah was defeated and slain; Ardebil then fell, after which Khazars spread across the country to loot and pillage. However, Said ibn Amr al-Harashi was now in command of Muslim forces, and, perhaps having learned from previous failures, he began to destroy the scattered Khazar detachments one by one. Eventually the two main armies came together on the Mugan steppe of north-western Iran. The Arabs were victorious; they overran the Khazar camp, regained lost booty, and almost captured Barjik himself.
Thereafter the war ground on with successes and failures on both sides, until a new Muslim commander, Maslama, decided that strategically vital Derbent must never be lost again. He strengthened its fortifications, established a military arsenal, and brought in a colony of Syrian troops with their families to garrison the citadel. Confident that no more could be done, Maslama handed over command to Marwan ibn Muhammad, a cousin of the caliph (who would later himself become the last Umayyad Caliph of Damascus as Marwan II). In 735, when Marwan offered to make peace, the Khagan sent an ambassador, but negotations turned sour. The Khazar ambassador was seized, and Marwan assembled an army reputedly numbering 150,000 men, including an Armenian detachment led by Prince Ashot. The size of this army enabled Marwan to divide his forces and invade Khazaria by two different routes.
Once he was deep inside Khazar territory, Marwan released the captive ambassador and sent him to the Khagan. The Khazar ruler fell back to a place the Arab chroniclers called al-Baida (‘the White’), which was probably part of the new Khazar capital of Atil. There he left an army, while he raised troops from regions of the Khaganate which had been untouched by the Islamic invasions. Instead of besieging al-Baida, Marwan led his army inland up the right bank of the Volga, eventually ravaging the distant lands of the Burtas, subjects of the Khazars on the northern frontier of the Khaganate. By now the Khagan had returned to shadow the Muslim army from the left bank of the Volga. So Marwan crossed the mighty river by night, using a pontoon bridge or bridges, probably where the river was divided by one or more islands◦– a remarkable feat of military engineering for the 8th century. A group of Arab scouts then killed a Khazar commander in a skirmish, after which Marwan’s army surprised the main Khazar force encamped. The Khazar Tarkhan or senior commander was killed during bitter fighting in which 7,000 Khazar soldiers were reportedly slain, with some 10,000 captured. The Khagan now sued for peace, but Marwan demanded that he convert to Islam. The Khazar leader agreed and◦– briefly◦– did become a Muslim, while also moving his capital to less vulnerable Atil on the Volga Delta.
Marwan ibn Muhammad’s remarkable campaign seemed to mark the triumph of Islam on this front. However, the Umayyad Caliphate was facing serious difficulties closer to home. Marwan ruled as the last Umayyad caliph from 744 to 750, but was then killed and his regime replaced by the new Abbasid Caliphate centred in Iraq. This tumult in the Islamic heartlands enabled the Khazars to rebuild their power, and in 764 a Khazar commander known as Ras Tarkhan invaded Azerbaijan and eastern Georgia within what was now the Abbasid Empire.
Thereafter relations between Khazar Khagans and Abbasid Caliphs remained stable and, after a century of intermittent warfare, the struggle seemed to have ended in a draw. Nevertheless, the Khazar Khaganate had halted the spread of Islam into South-Eastern Europe, providing time and space for Russia to become Christian. The Khaganate had also sometimes served as a valuable strategic ally of the Byzantine Empire during its struggle for survival.
BYZANTINE-KHAZAR WARS, 8th–10th CENTURIES
Despite facing a common foe in the Umayyad and subsequently Abbasid Caliphates, the Khazar Khaganate and Byzantine Empire had their own disputes. One episode saw the Khazars supporting King Leon II of Abkhazia (767–768 and 811–812), whose mother was a daughter of the Khazar Khagan, in a successful bid to free himself from Byzantine overlordship and apparently exchange it for Khazar suzerainty.
A more important arena of rivalry was the Crimean peninsula, which, although inhabited by Christians, was largely under Khazar rule. Tensions became acute in 787 when an uprising broke out in Gothia, a Goth principality in south-western Crimea. This relic of earlier Germanic rule was under Khazar suzerainty, and a local Christian bishop named John put himself at the head of the rebellion. A Khazar garrison was expelled from the regional capital of Doros (now Mangup), and the rebels seized control of mountain passes controlling access to the coast. Unwilling to accept this situation, the Khazar Khagan speedily regained Doros, capturing but not executing Bishop John. Since the Khaganate was then a powerful state, the Byzantines who controlled part of the Crimean coast chose not to intervene immediately.
At the start of the 9th century Byzantium took advantage of a civil war in Khazaria between the Khazars and their Magyar vassals, and overran Crimean Gothia apparently with almost no resistance◦– perhaps one of the competing forces within the Khaganate wanted Byzantine support. What seems certain is that Khagan Obadiah was so preoccupied with problems at home that he let Gothia go.