Bahram Chobin originally started his career as "marzban" of Ray, but in 572 he commanded a cavalry force and took part in the siege and capture of the key Byzantine stronghold of Dara and was promoted to army chief ("spahbed") of the "North" (Adurbadagan and Greater Media). After being promoted he fought a long, indecisive campaign in 572–591 against the Byzantines in northern Mesopotamia. In 588, the Turkic Khagan Bagha Qaghan (known as Sabeh/Saba in Persian sources), together with his Hephthalite subjects, invaded the Sasanian territories south of the Oxus, where they attacked and routed the Sasanian soldiers stationed in Balkh, and then proceeded to conquer the city along with Talaqan, Badghis, and Herat.