This question seems good, but the context is a little off. What exactly began in the 13th century? Migrations and invasions from the Eurasian Steppe go back (at least) to the Indo-Europeans in he early 3rd millennium BCE, followed by Iranian groups like Cimmerians, Scythians, Alans, the Huns (whoever they were), Turkic peoples like Bulgars, Khazars, Pechnegs, Cumans, the Ugric M