Titus Livius (Livy), The History of Rome, Book 21
Benjamin Oliver Foster, Ph.D., Ed.

52. Now that both the consuls and all the forces which the Romans could muster were opposing Hannibal, it was obvious enough either that the troops there under arms were able to defend Rome's empire or that her case was hopeless. [2] Nevertheless one of the consuls, disheartened by a single cavalry engagement and weak from his wound, preferred to postpone the decision. The other, unwearied and therefore the more impetuous, would put up with no delay.

[3] The country between the Trebia and the Po was in those days inhabited by Gauls, who in this struggle of two mighty peoples maintained a neutral attitude and plainly intended to court the good-will of the victor. [4] This policy was agreeable enough to the Romans, if only the Gauls made no disturbance, but was far from acceptable to Hannibal, who declared repeatedly that he had come on the invitation of the Gauls, to set them free. [5] In his resentment at this state of affairs, and in order at the same time to sustain his troops with plunder, he ordered two thousand foot and a thousand horse —chiefly Numidians but with a sprinkling of Gauls —to [6] waste the entire country-side, field after field, right up to the banks of the Po. The helpless Gauls, who had been undecided until then, were compelled to turn from the authors of their wrongs to those who might avenge them; and, sending envoys [p. 155]to the consuls, besought the Romans to come to the¹ aid of a land that was suffering for its inhabitants' too great loyalty to Rome. [7] Cornelius liked neither the occasion nor the time for fighting, and regarded the Gauls with suspicion, both because of many acts of perfidy, and especially —even though time had obliterated those ancient grievances —because of the recent treachery of the Boi. [8] Sempronius, on the contrary, held that the strongest bond for keeping the allies to their obligations was the defence of those who should first stand in need of help. [9] On the present occasion, while his colleague hesitated, Sempronius sent his cavalry, interspersed with about a thousand foot-soldiers, armed with darts, to protect the Gallic lands beyond the Trebia. [10] Falling unexpectedly upon the enemy, who were scattered and disorganized —most of them laden too with spoils —they drove them with great slaughter in a terror-stricken rout to the very outposts of the Carthaginian camp. Thence the enemy poured out in numbers and repulsed the Romans, in their turn; but reserves came up and restored the day. [11] Thereafter the fortune of the battle shifted, as pursuit was followed by retreat; and though in the end the opposing armies were on even terms, still the enemy had lost more men and the Romans got the credit of a victory.