The history of much of the world over the past two thousand years can be seen as a series of invasions by conquering hordes.
The prototype is the fall of the Roman Empire. An, urban, literate civilization is overrun and destroyed by savages.
In the middle of the fifth century, Attila the Hun and a host of other nomadic tribes deal Rome the coup de grace, officially terminating the West Roman Empire in 476 A.D. The Huns were of Uralo-Altaic origin. They came roaring out of the central Asian steppes.
Other barbarian tribes descending on Italy and other parts of Western Europe include the Visigoths (A.D. 410), the Vandals (455), the Ostrogoths (488), the Lombards (568) and many others. Most emanated from the East, although some, for example the Franks (405), came from the North.
My geography of these population movements is Eurocentric: I see a sedentary, advanced civilization in the West, overrun and destroyed by primitive, warlike, nomadic tribes often originating in Asia.
Granted, the tribes that invaded the Roman Empire were in some primitive ways more “democratic.” Granted, also, that many tribes such as the Visigoths were themselves being chased westward by the fierce Huns, seeking Rome’s protection. I merely summarize a process in broad strokes.
It continues after the fall of Rome: Medieval Christian Europe faces repeated onslaughts. The Magyars (my own ancestors) settle Pannonia (Hungary) at the end of the 9th century. The Ottoman Empire, beginning around 1300 AD, sacks Constantinople, putting an end to the East Roman Empire in 1453, reaches the gates of Vienna and occupies Hungary for a century and a half.