Titus Livius (Livy), The History of Rome, Book 27
Frank Gardner Moore, Professor Emeritus in Columbia University, Ed.

48. First Nero with all the cavalry arrived, then Porcius with the light-armed caught up with them. [2] And while they made skirmishing attacks from every side and charged the weary column, and the Carthaginian, now abandoning a march which resembled a flight, was aiming to lay out a camp on the hill above the bank of the river, came Livius with [3??] all the infantry forces, not in marching order, but formed and armed to begin the battle at once. [4] But after they had combined all their troops and the line had been drawn up, Claudius on the right wing,¹ Livius on the left, prepared for battle, while the command of the centre was assigned to the praetor. [5] Hasdrubal, on seeing that he must fight, ceased fortifying his camp and placed his elephants in the front line before the standards. Flanking the elephants,² on the left wing he placed the Gauls facing Claudius —not so much that he trusted them, as that he believed the enemy was afraid of them. [6] The right wing facing Marcus Livius he took for himself and his Spanish troops, and above all he rested his hopes on these veteran soldiers.³ [7] The Ligurians were placed in the centre behind the elephants. But the battle-line was deep rather than widely extended. A projecting hill shielded the Gauls. [8] That part of the front which the Spaniards held clashed with the left wing of the Romans, whose [p. 401]whole right wing extended beyond the fighting and⁴ had nothing to do. The hill facing them prevented them from attacking either in front or on the flank.

[9] Between Livius and Hasdrubal a mighty battle had begun, and a savage slaughter on both sides was in progress. [10] There both generals⁵ were engaged, there the greater part of the Roman infantry and cavalry, there the Spanish troops, the old soldiers, acquainted also with the Roman mode of fighting, and the Ligurians, a hardy race of warriors. To the same place came the elephants, which had thrown the front lines⁶ into confusion by their first charge and had by this time forced the standards back. [11] Then as the conflict and the shouting increased, they were no longer under control and roamed about between the two battle-lines,⁷ as though uncertain to whom they belonged, not unlike ships drifting without their steering-oars. [12] Claudius shouted to his soldiers, “Why then have we covered so long a march at headlong speed?” and endeavoured without success to lead his line up the hill. [13] Thereupon, after discovering that they could not get to the enemy in that direction, he drew off a number of cohorts from the right wing, where he saw that they would be standing idly by instead of fighting. [14] He led them round behind the battle-line,⁸ and to the surprise not only of the enemy, but also of his own troops, charged into the enemy's right flank. And such was his speed that, soon after showing themselves on the flank, they were already attacking the rear. Thus from all sides, front, flank, rear, the Spaniards and Ligurians [p. 403]were slain, and the slaughter had now reached the⁹ Gauls. [15] At that point there was the least fighting; for a large proportion of them were not with the standards, having slipped away in the night and lying asleep scattered over the fields. [16] And further, those who were present, being exhausted by marching and lack of sleep, lusty, but utterly lacking in endurance, could scarcely carry their arms on their shoulders. [17] And now it was midday, and thirst and heat exposed the gasping men to unlimited slaughter or capture.