The empire of Charlemagne was next to be assailed by the Huns, not the same people whose fathers had fought under Attila, though probably descended from the same stock. Upon the death of that ferocious conqueror, the tribes whom his talents had kept united, again sundered. Shortly afterward a warlike nation, calling themselves Avars, approached the northern parts of Europe, having been driven from their native country by the Turks. They spread rapidly, acquiring territory and power, until they were invited by Tassilo to aid him in his meditated treachery. They lost more than one battle against the Franks, but neither their own defeat, nor the total overthrow of their ally, made any change in their purposes. They persisted; fought a hard battle, and were so utterly routed, that they drew back and remained quiet for a while, in order to collect their strength before venturing upon a fresh contest with their tremendous adversary, who, on his part, was no less desirous of a respite for the same object. Little rest, however, was allowed him. No sooner had he beaten back these Huns, than he had to contend with a new enemy, the Weletabes, a Slavonian tribe inhabiting the northern part of Germany, near Brandenburg and Pomerania, from the Elbe to the Baltic. In themselves they might not have excited much alarm, but, if they met with only a temporary success, their example might have been fatal, by rousing the Saxons, who still with reluctance submitted to the yoke imposed upon them. The king, therefore, without loss of time, met and defeated the Weletabes; when he received them into grace, and ever afterward found them faithful. Having freed himself from this peril, Charlemagne next found that he must turn his arms against the Huns of Hungary, which appears to have been defended by them after a singular fashion. The whole country was surrounded by nine circles of double palisading, formed of trunks of trees twenty feet in height. The interstices of the palisade were twenty feet wide, filled with stone and lime compacted, the top being covered with earth, and planted with shrubs. At the distance of twenty Teutonic, or forty Italian miles, was a second fortified line of the same kind; and thus the circles were repeated, the circumference always narrowing till you came to the innermost, or ring, in which the Avars kept all their wealth, the accumulation of centuries of rapine. Such, at least, is the account, however improbable, handed down to us by an historian of the day. In the outset fortune favored Charlemagne as usual. He took the first three of the defensive circles sword in hand, and laid waste the country to the junction of the Raab with the Danube, while his son Pepin had met and routed their army in another quarter. But unhappily a pestilential disease broke out among the horses, who died by thousands, and he was obliged to retreat, unpursued, however, by the Avars, their surprise and terror not having yet subsided.