Khazars (Yarmuk)

The Khazars, an offshoot of the Turkish Khanate which, at its height, dominated the Russian Steppe area, were a shortlived but powerful state and were firm trading partners with the Byzantines. There eventual destruction by the Ummuyad Caliphate, proved to be a great blow to there allies in Constantinople - and left the Transoxianian area open to Seljuk advance.