Res Gestae

And so a great number of them lay there pierced with mortal wounds, begging for death as a speedy relief; others half-dead, with their spirit already slipping away, sought with dying eyes for longer enjoyment of the light; some had their heads severed by pikes heavy as beams, so that they hung down, connected only by their throats; some had fallen in their comrades’ blood on the miry, slippery ground, and although their persons were untouched by the steel, they were perishing, buried beneath the heaps of those who kept falling above them.

When all this had turned out so very successfully, our victorious troops pressed on with greater vigour, blunting the edges of their swords with stroke after stroke, while gleaming helms and shields rolled about under foot. At last the savages, driven on by the utmost extremity, since the heaps of corpses were so high as to block their passage, made for the only recourse left, that of the river, which now almost grazed their backs.

And since

As a result it was seen that they stood on the banks and transfixed the Germans with various kinds of darts; and if any of them by his speed escaped this death, he would sink to the bottom of the river through the weight of his struggling body.