I just finished reading and collating into a PDF book, Arthur Koestler’s 1976 manuscript entitled, “The Thirteenth Tribe.” There are many websites that speak of the Khazar Jews and their history, but this book best explains the story. Koestler is a Hungarian Jew, which makes him a Khazar Jew, as well. His work is not a condemnation but an honest look at world wide Jewry, which divides into 10% Sephardic (i.e., Spanish) and 90% Ashkenazi (i.e., Russian), of which those Ashkenazi Jews are Khazars from the gentile tribe descended from Japheth and not Shem. Koestler draws upon original and second hand manuscripts from Arabic, Jewish, Russian, Byzantium, Spanish and English documents. The Khazars come from the Russian steppes of Turkmenistan and settled between the Black and Caspian Seas, which today is Georgia and Ukraine.