The Jewish author, Arthur Koestler, relates the following concerning Jewish history: In his 1976 bestseller The Thirteenth Tribe, the Author of Darkness at Noon, Promise and Fulfillment, and The Roots of Coincidence dropped another bombshell by proving that today’s Jews were, for the most part, descendants of Khazars, who converted to Judaism seven centuries after the destruction of Jerusalem in 70 A.D.
"This, of course, is inspired by the story of the Covenant in Genesis; and it implies that the Khazars too claimed the status of a Chosen Race, who made their own Covenant with the Lord, even though they [Khazars] were not descended from Abraham’s seed ... He cannot, and does not, claim for them [the Khazars] Semitic descent, he traces their [Khazars] ancestry not to Shem, but to Noah’s third son, Japheth or more precisely to Japheth’s grandson, Togarma, the ancestor of all Turkish tribes.
'We have found in the family registers of our fathers,' Joseph asserts boldly, 'that Togarma had ten sons, and the names of their offspring are as follows: Uigur, Dursu, Avars, Huns, Basilii, Tarniakh, Khazars, Zagora, Bulgars, Sabir. We [Khazars] are the sons of Khazar, the seventh...'"
(The Thirteenth Tribe, Arthur Koestler, pages 58-82)