IT is time now to turn to the East, where development, as important for European history as that in the West, is much more obscure. New tribes and nations, known but dimly if at all to Rome, appear on the scene. Beiore the Christian era the north-westward trek from Asia had carried Finno-Ugrian tribes to the Volga and then northward across the north of Russia into Finland and down the shores of the Baltic. German tribes had flowed east and founded short-lived empires in the steppes before returning to assail the West. The Huns had swept over them like a devastating fire, and into the emptiness new invaders emerged slowly from Asia, founding kingdoms. From their original fastnesses in the marshlands of the Pripet, where they had multiplied in security from the nomad horsemen, the Slavs pushed northward, eastward, westward, southward, covering much of Russia and pressing the Finnish tribes northward, colonising Germany to the west of where Berlin now stands, crossing the Carpathians and flooding the Danube plain, reaching the Adriatic and penetrating the Balkans. Long before their expansion was completed, those in Central Europe had been conquered by the Avars who, as a nomad aristocracy ruling a nation of peasant slaves, threatened West and East alike, nearly reached Constantinople, and challenged Charles the Great, only to be defeated and disappear before the end of the eighth century. Earlier there existed a mysterious and somewhat uncertain Slav empire in the Danubian area, but it was not until the domination of the Avars was broken, and on every side the Slavs were coming into contact with Christian civilisations, that the Slavs began to coalesce into states- usually around the old centres of organised political life. The eighth century saw the creation by the Poles 'of a state of Poland, by the Czechs of Bohemia, by the Croats of Croatia, by the Serbs of Serbia. The process was slow. The Slav showed little genius for state building, and his greatest achievements in that respect were due mainly to the inspiration of other races. But Slav heathendom occupied the greater part of Central, South-Eastern, and Eastern Europe, touching the encroaching Western civilisation in the west and bickering with Byzantium and mobile Asia in the east. Slav infiltration into classical Greece was the easier, as the Byzantine empire was again at grips with the Moslem. On the East, Saracens appeared on the Bosphorus ; in the West, winning command of the sea, they flooded Sicily, established themselves in South Italy, and compelled the Pope to organise the defence of Rome itself. For the Slav contact with civilisation was contact with Christianity. Not merely did Charles the Great in his victorious advance eastwards give his enemies, German, old Prussian, and Slav, the choice between conversion or death, but the missionary monk was proceeding methodically to the evangelisation of the pagans beyond the Elbe and the Danube. These Christian priests, some of whom penetrated into the East by the old trading ways-for along the old routes trade still moved as well as armies-preached the Cross and the primacy of Rome in the forests of Poland, on the shores of Pomerania and even on the fiords of Scandinavia. The conquests of the Roman Church roused the Greek Church, but it could not even supply missionaries equal to those of the West in the art of conversion. Cyril and Methodius were men of the East, but when they christianised the nearer Slavs they converted them to Rome, and thus not only added to the adherents of the Western Church the most virile portion of a mighty race, but set up a new dividing line between Western and Eastern Europe.