As governor of the Caliphate's Caucasian provinces, Yazid played a central role in the brief recurrence of conflict with the Khazar Khaganate, the Caliphate's northern neighbour: in 759 or 760, in an effort to improve relations with the Khazars, al-Mansur ordered him to marry a daughter of the Khazar "khagan". Baghatur gladly accepted and sent her south with a large and rich escort, as well as 100,000 "dirhams" as her dowry. The marriage indeed took place, but after two years the princess and her two children suddenly died, and the "khagan" suspected that she had been poisoned. As a retaliation, he launched devastating raids south of the Caucasus in 762–764: under the leadership of a Khwarezmian "tarkhan" named Ras, the Khazars devastated Caucasian Albania, Armenia, and Iberia, where they captured Tiflis. Yazid himself managed to escape capture, but the Khazars returned north with thousands of captives and much booty. Yazid also campaigned with distinction against the Byzantines, recovering the city of Theodosiopolis/Qaliqala, which had been captured by the Byzantine emperor Constantine V, in the 750s, and leading summer raids into Asia Minor in 772, 774 and 779.