The Ashkenazim are thought to have emerged from dispersals north into the Rhineland of Mediterranean Jews in the early Middle Ages, although there is little evidence before the twelfth century
5,
15. After expulsions from Western Europe between the thirteenth and fifteenth centuries, the communities are thought to have expanded eastwards, especially in Poland, Lithuania and then Russia. The implied scale of this expansion has led some to argue, again very controversially, for mass conversions in the Khazar kingdom, in the North Caucasus region to the north and east of the Black Sea, following the Khazar leadership’s adoption of Judaism between the ninth and tenth centuries CE
8,
9.