By this time the Roman left wing, ,vhere the allied cavalry were fronting the Numidians, had become engaged, but the fighting was slack at first owing to a Carthaginian stratagem. About 500 Numidians, carrying, besides their usual arms and missiles, s,vords concealed under their coats of mail, rode out from their own line with their shields slung behind their backs as though they ,vere deserters, and suddenly leaped from their horses and flung their shields and javelins at the feet of their enemy. They were received into their ranks, conducted to the rear, and ordered to remain quiet. \Vhile the battle was spreading to the various parts of the field they remained quiet, but when the eyes and minds of all were wholly taken up with the fighting they seized the large Roman shields which were lying everywhere amongst the heaps of slain and commenced a furious attack upon the rear of the Roman line. Slashing away at backs and hips, they made a great slaughter and a still greater panic and confusion. Amidst the rout and panic in one part of the field and the obstinate but hopeless struggle in the other, Hasdrubal, ,vho was in command of that arm, withdrew some Numidians from the centre of the right wing, where the fighting was feebly kept up, and sent them in pursuit of the fugitives, and at the same time sent the Spanish and Gaulish horse to the aid of the Africans, who were by this time more wearied by slaughter than by fighting.