The Hazar State had be the best allied of Byzantium against Iran. The Sasani Empire, that weakened in the years 634-637 due to the Turkish-Byzantian cooperation, had been brought to collapse by Islamic forces and the Iranian lands were taken over by the Arabics. As the Islamic movement started developing, from one side over Armenia to Caucasia, from the other side over Syria to the inner parts of Anatolia, this alliance had become natural. The political interests partnership, that strengthened more and more as from the 2nd half of the 7th decade last until the 8th century and gained so much of value and importance that marriages between these two emperor families were made. The Emperor Jusitnianos II (685-695 and 705-711) and Konstantinos V (741-775) had married Hazar princesses.
Leon IV (775-780), the son of Konstantinos and princess Çi-çek who is known in history as the emperor with the agnomen "Hazar Leon", had be the grandson of the Hazar khane. Therefore in the same time, in their own political-military matters the emperors made use of the Hazar help. Hazar Leon's wife Iren, who later on had not be "Augusta" or the emperor substitue, but was accepted on her own with full permission and proclaimed as "Basile-us" had been an event that was seen for the first time in the history of Byzantium and Rome can probably be explained by the Hazar-Turk influence.