Tavriya and khazar.
They were important allies of the Byzantine Empire against the Sassanid Empire and later the Caliphate, the Pechenegs, and the Rus'. In later years, however, once Khazaria had become a significant regional power, the Byzantines abandoned the alliance and turned to the Rus' and Pechenegs against the Khazars. In 965, their sovereignty was broken by Sviatoslav I of Kiev, and they became a subject people of Kievan Rus'. Gradually displaced by the Rus, the Kipchaks, and later the conquering Mongol Golden Horde, the Khazars largely disappeared as a culturally-distinct people.
Today, various proverbs invoking Khaza persist. Indeed, the Caspian Sea, traditionally known as the Hyrcanian Sea and Mazandaran Sea in Persian, came to be known to Iranians as the Khazar Sea.
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