 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 Turks sacked Derbent and joined the Byzantines in their siege of Tiflis . Their contribution proved decisive for the eventual Byzantine victory in the war . For a few years afterwards , until ca . 632 , the Khazars exercised some control over Caucasian Iberia ( approximately modern Georgia ) , Caucasian Albania ( modern Azerbaijan ) and Adharbayjan ( modern Iranian Azerbaijan ) . 
