The book is divided into two primary sections that trace the empire's rise and its alleged legacy: The Thirteenth Tribe: The Khazar Empire and Its Heritage
Arthur Koestler's 1976 book, , presents a provocative thesis that Ashkenazi Jews are primarily descended from the Khazars, a Turkic people, rather than ancient Israelites . Koestler's stated intent was to eliminate the racial basis for antisemitism by arguing that Jews were not a distinct "Semitic" race. Core Arguments and Structure Thirteenth Tribe: Khazar Empire and Its Heritage