1By now on the Roman left wing as well, where the allied cavalry had stood facing the Numidians, battle had been joined, sluggish at first and begun with a Carthaginian trick. 2About five hundred Numidians, who had swords hidden under their breastplates besides their usual arms and missiles, having ridden up from their own side in the guise of deserters with their shields behind their backs, suddenly leap down from their horses, and, throwing their shields and javelins at the feet of the enemy, are received into the middle of the line, led to the rear and ordered to sit down behind. 3And while battle was being joined on every side, they stayed quiet; 4but after the struggle had taken up everyone's minds and eyes, then, snatching up shields which lay strewn everywhere among the heaps of slain bodies, they attack the Roman line from behind, and striking at backs and hamstringing men they caused enormous slaughter and still greater panic and confusion.
5While in one place there was terror and flight, in another a stubborn battle despite hope now failing, Hasdrubal, who commanded in that quarter, sends the Numidians, withdrawn from the centre because their fight with those facing them was sluggish, to pursue the fugitives everywhere, and joins the Spanish and Gallic cavalry to the Africans, who were by now almost exhausted, more by slaughter than by fighting.