Titus Livius (Livy), The History of Rome, Book 25
Frank Gardener Moore, Professor Emeritus in Columbia University, Ed.

21. Near Herdonea¹ were Roman legions and the praetor Fulvius. When the news reached them there that the enemy were approaching, they barely refrained from catching up their standards and going out into battle-line without orders from the praetor. And nothing restrained them more than the hope, now beyond question, that they would do so at their own discretion whenever they pleased. [2] The following night Hannibal, knowing that there had been an uproar in the camp and that many, calling to arms, had over-confidently pressed the commander to give the signal, had no doubt that an opportunity for a victory was offered. [3] He accordingly posted three thousand lightly equipped soldiers in farmhouses near by and in the thickets and the woods, to come out of their hiding-places all at once, [p. 423]when the signal was given. [4] And he ordered Mago² and about two thousand horsemen to lie in wait along all the roads in the direction which he believed the flight would take. After making these preparations at night, he led his troops out into line at daybreak. [5] Nor did Fulvius hesitate, dragged into it not so much by any hope of his own as by the haphazard impulse of the soldiers. And so, with the same recklessness with which they went out to form, they drew up even the line of battle according to the whim of soldiers who happened to dash forward and take their stand wherever their own fancy had carried them, and then capriciously or in fear abandoned their positions. [6] The first legion and the left ala were placed in front,³ and the line was made very long. [7] Although the tribunes shouted that in depth it had no power to resist, and that wherever the enemy should make their attack they would pierce it, the men in line allowed no advice that was helpful to reach even their ears, not to say their attention. [8] And there was Hannibal, surely not that sort of a general, nor with that sort of an army, drawn up in that fashion. Consequently the Romans did not withstand even their shout and the first onset. [9] The general, a match for Centenius in folly and recklessness, but in courage by no means to be compared with him, seeing that the line was giving way and his own men in confusion, seized a horse and with about two hundred horsemen made his escape. [10] The rest of the line, beaten back in front and then surrounded in the rear and on the wings, was so cut to pieces that out of eighteen thousand men not more than two thousand escaped. The camp was occupied by the enemy.

[p. 425]