Northern Caucasus along the Caspian Sea.
The origin and history of the Khazars and Khazar kingdom and their relationship to the origin and early history of the so-called or self-styled Jews in eastern Europe was one of history's best kept secrets until wide publicity was given in recent years to my research on this subject. In the many wars with her neighbors in Europe after the 13th century Russia was required to cede to her victors large areas which were originally part of the Khazar Kingdom. In this manner Poland, Lithuania, Galicia, Hungary, Rumania, and Austria acquired from Russia territory originally a Khazaria: An Empire Gone by Ronny Carny. Between the 8th and 11th centuries there existed in Central Asia an empire powerful enough to rival that of the Byzantines, the Arabs, or the emerging Rus and European states. Khazar, a nation of Oghuric Turks, speaking a Chuvash dialect, played a pivotal role in history.  According to George Vernadski, in his book A History of Russia, in AD 860 a delegation of Khazars were sent to Constantinople (now known as Istanbul), which was then what remained of the ancient capitol of the old Roman Empire turned Christian under the Emperor Constantine. So as not to exclude the Islamic account of these events, the following is taken by D. M. Dunlop from al-Bakri's eleventh century work the Book of Kingdoms and Roads : The reason for the conversion of the king of the Khazars, who had previously been a heathen, to Judaism was as follows. In the narratives of Theophanes and Moses of Kalankatuk respectively, the Khazars are also called Turks and Huns. From 681 C.E., we hear much in the latter author of the Huns of Varach ʿ an (Warathān), north of Darband, who evidently formed part of a Khazar confederation or empire. The Reply of Joseph mentions that the Khazars guarded the mouth of the Volga before 961 C.E. and prevented the Russians from reaching the Caspian. On several occasions, notably c. 913 and again in 943, the Russians made raids down the Volga, passing through Atil. The Khazar kingdom was shattered, and the kingdom of the Khazars fell into decline. Eventually most of the Khazar Jews migrated to other areas. Many of them wound up in eastern Europe, where they mingled and intermarried with other Jews. Like the Semitic Jews some 1000 years earlier, the Khazar Jews became dispersed. To the south-east, the Khazar kingdom bordered on the expanding Moslem Empire of the Arab Caliphs. The Khazar's influenced the histories of both of these empires but, far more importantly, the Khazar kingdom occupied what was later to become a southern portion of Russia between the Black and Caspian Seas. A THOUSAND YEARS before the establishment of the Modern State of Israel, there existed a Jewish kingdom in the eastern fringes of Europe, astride the Don and Volga rivers.... So begins a thesis by Jewish author Kevin Alan Brook. So as not to exclude the Islamic account of these events, the following is taken by D. M. Dunlop from al-Bakri's eleventh century work the Book of Kingdoms and Roads : The reason for the conversion of the king of the Khazars, who had previously been a heathen, to Judaism was as follows. The Khazar theory of Ashkenazi ancestry is a hypothesis that Ashkenazi Jews descend from the Khazars-a multi-ethnic collection of Turkic peoples who formed a semi-nomadic Khanate in what is now Southern Russia, extending from Eastern Europe to Central Asia.  In the 7th century CE, the Khazars founded an independent khaganate, or kingdom, in the Northern Caucasus along the Caspian Sea. It is believed that during the 8th or 9th century, around the height of their kingdom, the state religion became Judaism at the order of the king. Map of the Khazar kingdom and surrounding regions, including Israel. This is a hugely important discovery, said the leader of the Russian expedition, Dmitry Vasilyev, in a report by the French agency AFP. from Koestler Website. KHAZAR. (Kazar, Chazar, Chozar, Chozr). This book traces the history of the ancient Khazar Empire, a major but almost forgotten power in Eastern Europe, which in the Dark Ages became converted to Judaism. The kingdom of the Khazars vanished from the map of the world many centuries ago. Today many people have never even heard of it yet in its day the Khazar kingdom [Khazaria] was a very major power, indeed holding sway over a large empire of subjugated peoples. To the south-east, the Khazar kingdom bordered on the expanding Moslem Empire of the Arab Caliphs. The Khazar's influenced the histories of both of these empires but, far more importantly, the Khazar kingdom occupied what was later to become a southern portion of Russia between the Black and Caspian Seas.
http://www.iahushua.com/JQ/factsR3.html http://econc10.bu.edu/economic_systems/NatIdentity/FSU/Caucasus/khazaria.htm http://www.apfn.org/THEWINDS/library/khazars.html http://www.jewishvirtuallibrary.org/jsource/Judaism/khazars.html http://www.orange-street-church.org/text/khazar.htm http://www.apfn.org/THEWINDS/library/khazars.html https://en.wikipedia.org/wiki/The_Ashkenazi_Jews/Khazarian_origins_theory http://www.israelnationalnews.com/News/News.aspx/127483 http://www.bibliotecapleyades.net/sociopolitica/esp_sociopol_khazar01.htm http://www.orange-street-church.org/text/khazar.htm
where was the khazar kingdom