[Borges]

Arthur Koestler thought that an Asiatic Tribe called the Khazars converted to Judaism in the 10th century or so and that Ashkenazi Jews are descendant from them. He put forward the theory in the hopes that it would deflect accusations from Deicide from contemporary Jews who would have no connection to Roman era JEws. Today the theory is favored by Neo Nazis and Muslims as it also invalidates Jewish claims to the Holy Land.

[Sherman Logan]

AS I understand it, DNA analysis has more or less disproved the Khazar theory.

While the Khazars did indeed “adopt Judaism,” it is likely that this applied primarily or only to the royal family and high aristocracy, not to the entire nation, which probably was dispersed anyway among the very fluid gene-mixing of the medieval steppe.

[Titus Quinctius Cincinnatus]

Arthur Koestler thought that an Asiatic Tribe called the Khazars converted to Judaism in the 10th century or so and that Ashkenazi Jews are descendant from them. He put forward the theory in the hopes that it would deflect accusations from Deicide from contemporary Jews who would have no connection to Roman era JEws. Today the theory is favored by Neo Nazis and Muslims as it also invalidates Jewish claims to the Holy Land.

The Kagan of the Khazars, and the aristocracy, converted to Judaism, but it's unlikely that the bulk of the common people did.