The Khazars (Greek: Χάζαροι, Hebrew: כוזרים (Kuzarim), Turkish: Hazarlar, Tatar: Xäzärlär, Arabic: خزر (khazar), Russian: Хазары, Persian: خزر,Latin: Gazari[/Cosri /Gasani]) were a semi-nomadic Turkic people who created what for its duration was the most powerful polity to emerge from the breakup of the western Turkish steppe empire, known as the Khazar Khanate or Khazaria. Astride a major artery of commerce between northern Europe and southwestern Asia, Khazaria became one of the foremost trading emporia of the medieval world, commanding the western marches of the Silk Road and played a key commercial role as a crossroad between China, the Middle East, and European Russia. For some three centuries (c. 650--965) the Khazars dominated the vast area extending from the Volga-Don steppes to the eastern Crimea and the northern Caucasus
Khazaria long served as a buffer state between the Byzantine empire and both the nomads of the northern steppes and the Umayyad empire, after serving as Byzantium's proxy against the Sassanid Persian empire. The alliance was dropped around 900 CE., as Byzantium began to encourage the Alans to attack Khazaria and weaken its hold on Crimea and the Caucasus, while seeking to obtain an entente with the rising Rus' power to Khazaria's north, which it aspired to convert to Christianity. Between 965 and 969, the Kievan Rus ruler Sviatoslav I of Kiev conquered the capital Atil and destroyed the Khazar state.
Beginning in the 8th century, Khazar royalty and notable segments of the aristocracy converted to Judaism; the populace appears to have been multi-confessional—a mosaic of pagan, Tengrist, Jewish, Christian and Muslim worshippers—and polyethnic. A modern theory, that the core of Ashkenazi Jewry emerged from a hypothetical Khazarian Jewish diaspora, is now viewed with scepticism by most scholars, but occasionally supported by others. This Khazarian hypothesis is sometimes associated with antisemitism and anti-Zionism.
Gyula Németh, following Zoltán Gombocz, derived Xazar from a hypothetical *Qasar reflecting a Turkic root qaz- ("to ramble, to roam") being an hypothetical velar variant of Common Turkic kez-. With the publication of the fragmentary Tes and Terkhin inscriptions of the Uyğur empire (744-840) where the form 'Qasar' is attested, though uncertainty remains whether this represents a personal or tribal name, gradually other hypotheses emerged. Louis Bazin derived it from Turkic qas- ("tyrannize, oppress, terrorize") on the basis of its phonetic similarity to the Uyğur tribal name, Qasar. András Róna-Tas connects it with Kesar, the Pahlavi transcription of the Roman title Caesar.
D.M.Dunlop tried to link the Chinese term for "Khazars" to one of the tribal names of the Uyğur Toquz Oğuz, namely the Gésà. The objections are that Uyğur Gesa/Qasar was not a tribal name but rather the surname of the chief of the Sikari tribe of the Toquz Oğuz, and that in Middle Chinese the ethnonym "Khazars", always prefaced with the word Tūjué signifying 'Türk' (Tūjué Kěsà bù:突厥可薩部; Tūjué Hésà:突厥曷薩), is transcribed with different characters than that used to render the Qa- in the Uyğur word 'Qasar'. After their conversion it is reported that they adopted the Hebrew script, and it is likely that, though speaking a Türkic language, the Khazar chancellery under Judaism probably corresponded in Hebrew.
Tribal origins and early history
The tribes constituting the Khazar union were, according to the most widely approved view, basically Turkic groups, such as the Oğuric peoples, including Šarağurs, Oğurs, Onoğurs, and Bulğars, who formed part of the Tiĕlè (鐵勒) confederation. These tribes, many driven out of their homelands by the Sabirs, who in turn fled the Asian Avars, began to flow into the Volga-Caspian-Pontic zone from as early as the 4th century CE and are recorded by Priscus to reside in the Western Eurasian steppelands as early as 463. They appear to stem from Mongolia and South Siberia in the aftermath of the fall of the Hunnic/Xiōngnú nomadic polities. A variegated tribal federation led by these Tűrks, probably comprising a complex assortment of Iranian, proto-Mongolic, Uralic, and Palaeo-Siberian clans, vanquished the Rouran Khaganate of the hegemonic central Asian Avars in 552 and swept westwards, taking in their train other steppe nomads and peoples from the Sogdian kingdom.