The Khazars themselves first campaigned in the Caucasus during the Byzantine-Sassanid War of 602-628, as a subject of the Western Turkic Khaganate.
The Khazars and the Arabs came into conflict as a result of the first phase of Muslim expansion: by 640, the Arabs had reached Armenia,[REF] and in 642, they launched their first raid across the Caucasus under Abd ar-Rahman ibn Rabiah [REF].