Arab–Khazar wars

The Arab–Khazar wars were a series of conflicts fought between the Khazar Khaganate and successive Arab caliphates in the Caucasus region from c. 642 to 799 CE. Smaller native principalities were also involved in the conflict as vassals of the two empires. Historians usually distinguish two major periods of conflict, the First Arab–Khazar War (c. 642 – c. 652) and Second Arab–Khazar War (c. 722 – c. 737); the wars also involved sporadic raids and isolated clashes from the mid-seventh century to the end of the eighth century.

The wars were a result of attempts by the nascent Rashidun Caliphate to secure control of the South Caucasus (Transcaucasia) and North Caucasus, where the Khazars were already established since the late 6th century. The first Arab invasion began in 642 with the capture of the strategically important city of Derbent that guarded the eastern passage of the Caucasus along the Caspian Sea, and continued with a series of minor raids, ending with the defeat of a large Arab force led by Abd al-Rahman ibn Rabi'a outside the Khazar town of Balanjar in 652. Large-scale hostilities then ceased for several decades, apart from raids by the Khazars and the North Caucasian Huns on the autonomous principalities of the South Caucasus during the 660s and 680s.

The conflict between the Khazars and the Arabs (now under the Umayyad Caliphate) resumed after 707 with occasional raids back and forth across the Caucasus Mountains, intensifying after 721 into a full-scale war. Led by the prominent generals al-Jarrah ibn Abdallah and Maslama ibn Abd al-Malik, the Arabs recaptured Derbent and the southern Khazar capital of Balanjar; these successes had little impact on the nomadic Khazars, however, who continued to launch devastating raids deep into the South Caucasus. In a major 730 invasion, the Khazars decisively defeated Umayyad forces at the Battle of Ardabil, killing al-Jarrah; in turn, they were defeated the following year and pushed back north. Maslama then recovered Derbent, which became a major Arab military outpost and colony, before he was replaced by Marwan ibn Muhammad (the future caliph Marwan II) in 732. A period of relatively localized warfare followed until 737, when Marwan led a massive expedition north to the Khazar capital Atil on the Volga. After securing the submission of the Khazar ruler, the khagan, the Arabs withdrew.

The 737 campaign marked the end of large-scale warfare between the two powers, establishing Derbent as the northernmost outpost of the Muslim world and securing Muslim dominance of the South Caucasus, but leaving the North Caucasus in Khazar hands. At the same time, continuing warfare weakened the Umayyad army and contributed to the fall of the Umayyad dynasty in 750, as a result of the Abbasid Revolution that established the Abbasid Caliphate. Relations between the Muslims of the Caucasus and the Khazars remained largely peaceful thereafter and the Caucasus became an avenue of trade linking the Middle East to Eastern Europe; peace was interrupted by two Khazar raids in the 760s and in 799 resulting from failed efforts to secure an alliance through marriage between the Arab governors (or local princes) of the Caucasus and the Khazar khagan. Occasional warfare between the Khazars and the Muslim principalities of the Caucasus continued until the collapse of the Khazar state in the late 10th century, but it never matched again the intensity and scale of the eighth-century war.