This original edition presents the provocative and widely debated thesis of Arthur Koestler, who argues that a significant portion of Ashkenazi Jewish ancestry may not trace directly back to the ancient Israelites of the Near East, but instead to the Khazars—a semi-nomadic Turkic people who established a powerful empire between the Black Sea and the Caspian Sea.

Koestler explores the historical account that the Khazar ruling elite, and possibly broader segments of the population, converted to Judaism during the 8th century. This unique event—where an entire polity is believed to have adopted Judaism—forms the foundation of his hypothesis. As the Khazar Empire declined between the 10th and 13th centuries, Koestler proposes that its Jewish populations migrated westward into Eastern and Central Europe.

According to this theory, these migrating groups settled across regions that now include Ukraine, Poland, Belarus, Lithuania, Hungary, and Germany. Over time, these communities are said to have formed the core of what later became known as Ashkenazi Jewry.

Koestler’s work attempts to reinterpret the ethnogenesis of Ashkenazi Jews through a Eurasian lens, challenging traditional narratives that emphasize direct descent from ancient Israelite populations. His argument draws upon historical chronicles, linguistic observations, and cultural connections, aiming to reconstruct a largely overlooked chapter of medieval history.

However, it is important to note that this thesis remains highly controversial. While the Khazar conversion to Judaism is broadly acknowledged by historians, the extent to which modern Ashkenazi populations descend from the Khazars is disputed. Contemporary research in genetics, archaeology, and historical studies has generally found stronger evidence supporting Middle Eastern origins mixed with European influences, rather than a primary Khazar lineage.

Today, this work is regarded as an influential but debated contribution to historical and cultural discourse—valued for its bold inquiry and narrative scope, yet approached critically within modern scholarship.