It is probable that there were two chief causes for the new westward drift of the nomadic Mongolians. One was the consolidation of the great empire of China, its extension northward and the increase of its population during the prosperous period of the Han dynasty. The other was some process of climatic change; a lesser rainfall that abolished swamps and forests perhaps, or a greater rainfall that extended grazing over desert steppes, or even perhaps both these processes going on in different regions but which anyhow facilitated a westward migration. A third contributary cause was the economic wretchedness, internal decay and falling population of the Roman Empire. The rich men of the later Roman Republic, and then the tax-gatherers of the military emperors had utterly consumed its vitality. So we have the factors of thrust, means and opportunity. There was pressure from the east, rot in the west and an open road. The Hun had reached the eastern boundaries of European Russia by the first century A.D., but it was not until the fourth and fifth centuries A.D. that these horsemen rose to predominance upon the steppes. The fifth century was the Hun’s century. The first Huns to come into Italy were mercenary bands in the pay of Stilicho the Vandal, the master of Honorius. Presently they were in possession of Pannonia, the empty nest of the Vandals. By the second quarter of the fifth century a great war chief had arisen among the Huns, Attila. We have only vague and tantalizing glimpses of his power. He ruled not only over the Huns but over a conglomerate of tributary Germanic tribes; his empire extended from the Rhine cross the plains into Central Asia. He exchanged ambassadors with China. His head camp was in the plain of Hungary east of the Danube. There he was visited by an envoy from Constantinople, Priscus, who has left us an account of his state. The way of living of these Mongols was very like the way of living of the primitive Aryans they had replaced. The common folk were in huts and tents; the chiefs lived in great stockaded timber halls. There were feasts and drinking and singing by the bards. The Homeric heroes and even the Macedonian companions of Alexander would probably have felt more at home in the camp-capital of Attila than they would have done in the cultivated and decadent court of Theodosius II, the son of Arcadius, who was then reigning in Constantinople. For a time it seemed as though the nomads under the leadership of the Huns and Attila would play the same part towards the Græco-Roman civilization of the Mediterranean countries that the barbaric Greeks had played long ago to the Ægean civilization. It looked like history repeating itself upon a larger stage. But the Huns were much more wedded to the nomadic life than the early Greeks, who were rather migratory cattle farmers than true nomads. The Huns raided and plundered but did not settle.