But the Slavs were a far more serious danger to the empire than the Avars. The latter came only to plunder, the former—like the Germans two centuries before—came pressing into the provinces to win themselves a new home. The Romans knew at first of only two tribes of them, the Slovenes and Antae, but behind these there were others who were gradually to push their way to the south and make their presence known—Croats, Servians, and many more. The Slavs were the easternmost of the Aryan peoples of Europe, and by far the most backward. They had always lain behind the Germans, and it was only when the German barrier was removed by the migration of the Goths and Lombards that they came into touch with the empire. They were rude races, far behind the Teutons in civilization; they had hardly learnt as yet the simplest arts, knew nothing of defensive armour, and could only use for boats tree-trunks hollowed out by fire—like the Australian savages of to-day. They had not learnt to live under kings or chiefs, but dwelt in village communities, governed by the patriarchs of the several families. Their abodes were mud huts, and they cultivated no grain but millet. When they went to war they could send out thousands of spearmen and bowmen, but their wild bands were not very formidable in the open field. They could resist neither cavalry nor disciplined infantry, and were only formidable in woods and defiles, where they formed ambuscades and endeavoured to take their enemy by surprise, and overwhelm him by a sudden rush. We are assured that one of their favourite devices was to conceal themselves in ponds or rivers by lying down in the water for hours together, breathing through reeds, whose points were the only things visible above the surface. Thus a thousand men might be concealed, and nothing appear except a bed of rushes. This strange stratagem would seem incredible, if we had not on record one or two occasions on which it was actually practised. The Slavs had begun to make themselves felt early in the sixth century, but it was not till the death of Justinian that we hear of them as a pressing danger. But when the Lombards had passed away westward, they came down to the Danube and began to cross it in great numbers, in the endeavour to make permanent settlements on the Roman bank. The raids of the Slavs and the Avars were curiously complicated, for the king, or Chagan, of the Tartar tribe had made vassals of many of his Slavonic neighbours. They, on the other hand, sometimes acted in obedience to him, but more frequently tried to escape from his power by pushing forward into Roman territory. Hence it comes that we often find Slav and Avar leagued together, but at other times find them acting separately, or even in opposition to each other. A more chaotic series of campaigns it is hard to conceive.