I haven't watched the above videos yet, but Arthur Koestler's book titled 'The Thirteenth Tribe' gives an in depth detailed account of the Khazar Empire converting to Judaism.
http://www.biblebelievers.worthyofpraise.org/13trindx.htm
THE KHAZAR EMPIRE AND ITS HERITAGE
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. Khazaria was finally wiped out by the forces of Genghis Khan, but evidence indicates that the Khazars themselves migrated to Poland and formed the cradle of Western Jewry. . .
The Khazars' sway extended from the Black Sea to the Caspian, from the Caucasus to the Volga, and they were instrumental in stopping the Muslim onslaught against Byzantium, the eastern jaw of the gigantic pincer movement that in the West swept across northern Africa and into Spain.
In the second part of this book, "The Heritage," Mr. Koestler speculates about the ultimate faith of the Khazars and their impact on the racial composition and social heritage of modern Jewry. He produces a large body of meticulously detailed research in support of a theory that sounds all the more convincing for the restraint with which it is advanced. Yet should this theory be confirmed, the term "anti-Semitism" would become void of meaning, since, as Mr. Koestler writes, it is based "on a misapprehension shared by both the killers and their victims. The story of the Khazar Empire, as it slowly emerges from the past, begins to look like the most cruel hoax which history has ever perpetrated."
A book by an adulterous, atheist, ex-Jewish dropout of engineering school proves nothing. Serious researchers have discredited everything he said, and DNA analysis has proven the Khazar hypothesis wrong time after time.
What other sources have you got for this? Anything credible by someone outside of the tinfoil-hat crowd?
What's behind all of this anyway? An attempt to discredit the state of Israel? There have been Jews living in Palestine continuously for thousands of years. Christians were unable to hold onto the Holy Land. Let the Jews have a whack at it. Their dreams of rebuilding the Temple will come to naught, just like the Moslems' aspirations will.
