Throughout the fifth, sixth, seventh and eighth centuries, there was a steady drift of Mongolian peoples westward. The Huns of Attila were merely precursors of this advance, which led at last to the establishment of Mongolian peoples in Finland, Esthonia, Hungary and Bulgaria, where their descendants, speaking languages akin to Turkish, survive to this day. The Mongolian nomads were, in fact, playing a role towards the Aryanized civilizations of Europe and Persia and India that the Aryans had played to the Ægean and Semitic civilizations ten or fifteen centuries before.
In Central Asia the Turkish peoples had taken root in what is now Western Turkestan, and Persia already employed many Turkish officials and Turkish mercenaries. The Parthians had gone out of history, absorbed into the general population of Persia. There were no more Aryan nomads in the history of Central Asia; Mongolian people had replaced them. The Turks became masters of Asia from China to the Caspian.
The same great pestilence at the end of the second century A.D. that had shattered the Roman Empire had overthrown the Han dynasty in China. Then came a period of division and of Hunnish conquests from which China arose refreshed, more rapidly and more completely than Europe was destined to do. Before the end of the sixth century China was reunited under the Suy dynasty, and this by the time of Heraclius gave place to the Tang dynasty, whose reign marks another great period of prosperity for China.