The Thirteenth Tribe القبيلة الثالثة عشرة

Blurb

The Thirteenth Tribe is a 1976 book by Arthur Koestler, in which he advances the thesis that Ashkenazi Jews are not descended from the historical Israelites of antiquity, but from Khazars, a Turkic people. Koestler's hypothesis is that the Khazars migrated westwards into Eastern Europe in the 12th and 13th centuries when the Khazar Empire was collapsing.
Koestler used previous works by Abraham Poliak, Raphael Patai and Douglas Morton Dunlop as sources. His stated intent was to make antisemitism disappear by disproving its racial basis.
Popular reviews of the book were mixed, academic critiques of its research were generally negative, and Koestler biographers David Cesarani and Michael Scammell panned it.