Almost as uncertain is the exact time when the Southern Slays began to move towards the Balkans. If already at the time of Trajan's conquests there were Slays in Dacia, it would account for the story in Ps. Nestor that certain Volchi or Vlachi, i.e., Romance speakers, had conquered the Slays upon the Danube and driven them to the Vistula, for the place that the name of Trajan has in Slavonic tradition, and for the presence of an agricultural population, the Sarmatae Limigantes subject to the nomad Sarmatae on the Theiss. In any case, we cannot say that the Slays occupied any large parts of the Balkan Peninsula before the beginning of the 6th century, when they appear in Byzantine history as a new terror ; there seems to have been an invasion in the time of Justin, and another followed in 527 (Procopius, B.G. iii. 4o and Hist. Arc. 18). At the same time as the Slays, the Huns, the Bulgars, and of ter 558 the Avars, were also making invasions from the same direction. The first and last disappeared like all nomads, but the Bulgars, making themselves lords of one section of the Slays, gave it their own name. By 584 the Slays had over run all Greece, and were the worst western neighbours of the Eastern Empire. Hence the directions how to deal with Slays in the Strategicum of the emperor Maurice (c. 600) and the Tactics of Leo.
By the end of the following century they were permanently settled throughout the whole of the Balkan Peninsula. These Southern Slays, though divided into nationalities, are closely akin to one another. There is no reason to think the Serbo-Croats
an intrusive wedge, although Constantine Porphyrogenitus (De adrn. Imp. 3o-33) speaks of their coming from the north in the time of Heraclius—the middle of the 7th century. Their dialects shade into one another, and there is no trace of any influence of the North-Western group. Constantine was probably led astray by the occurrence of the same tribal names in different parts of the Slavonic world. Meanwhile the Southern Slays were cut off from the rest of the race by the foundation in the 6th century of the Avar kingdom in Pannonia, and after its destruction in the 7th, by the spread of the Germans south-eastwards, and finally by the incursion of another Asiatic horde, that of the Magyars, who have maintained themselves in the midst of Slays for a thousand years. Their conquests were made chiefly at the expense of the Slovenes and the Slovaks, and from their languages they have borrowed many words in forms which have now disappeared.
Of the history of the Eastern Slays, who were to become the Russian people, we know little before the coming of the Swedish Rus, who gave them their name and organization ; we have but the mention of Antae acting in concert with the other Slays and the Avars in attacking the Empire on the lower Danube, and scattered accounts of Muslim travellers, which show that they had reached the Don and Volga and stretched up northward to Lake Ilmen. The more southerly tribes were tributary to the Khazars.