There are many strands, subcategories and highly debated taxonomies within Judaism – governed by theology, doxology, jurisprudence, language and descent. The differences between the two main branches of Judaic communities, Sephardim (and Mizrahim) and Ashkenazim, are well known: they emerged from Judaic communities in the Islamic ummah and Christian oikoumene, respectively – with attendant geographical subcategories. Judaic communities also survived for centuries further south, east and beyond the Abrahamic worlds, such as Beta Israel and the Teimanim (Eastern Africa and Southern Arabia), Kaifeng Jews (western China) and Kochinim (southern India). All these communities date back centuries and their origins remain the subject of many discussions. However, one of the most contentious debates is about the origin of the Ashkenazim – or as typically described, the Jewish populations of Central and Eastern Europe.

There are two schematic theories about the origin of the Ashkenazim: that they settled in Central and Eastern Europe via a western route through Western Europe and/or via an eastern route through Caucasia and Khazaria. The former, termed the ‘Rhineland hypothesis’, is the most commonly accepted theory for Ashkenazi origins: according to this theory, following the diaspora in the wake of the Roman suppression of the second-century Bar Kokhba Revolt, Jewish communities emerged in second- to fifth-century Western Roman imperial provinces like Hispania, Gaul, Britannia and Italy, which remained until various thirteenth- to fourteenth-century anti-Jewish expulsions and Crusader violence, leading to eastward migrations towards Piast-ruled lands due to simultaneous legal protections granted by Piast kings.