The Thirteenth Tribe: The Kazar Empire and Its Heritage

Koestler advances the thesis that Ashkenazi Jews are not descended from the historical Israelites of antiquity but from Khazars a Turkic people originating in and populating an empire north of and between the Black Sea and Caspian Sea. Koestlers hypothesis is that the Khazars - who converted to Judaism in the 8th century - migrated westwards into current Eastern Europe (primarily Ukraine Poland Belarus Lithuania Hungary and Germany) in the 12th and 13th centuries when the Khazar Empire was collapsing.