The western part of this barbaric north from the German forests to South Russia and Turkestan and from Gothland to the Alps was the region of origin of the Nordic peoples and of the Aryan speech. The eastern steppes and deserts of Mongolia was the region of origin of the Hunnish or Mongolian or Tartar or Turkish peoples—for all these several peoples were akin in language, race, and way of life. And as the Nordic peoples seem to have been continually overflowing their own borders and pressing south upon the developing civilizations of Mesopotamia and the Mediterranean coast, so the Hunnish tribes sent their surplus as wanderers, raiders and conquerors into the settled regions of China. Periods of plenty in the north would mean an increase in population there; a shortage of grass, a spell of cattle disease, would drive the hungry warlike tribesmen south.
For a time there were simultaneously two fairly effective Empires in the world capable of holding back the barbarians and even forcing forward