After this, Hannibal fell into a grievous error. He wished to draw his army off some distance beyond Fabius, and occupy plains affording pasturage. He therefore ordered his native guides to conduct him, immediately after supper, into the district of Casinum. But they did not hear the name correctly, owing to his foreign way of pronouncing it, and promptly hurried his forces to the edge of Campania, into the city and district of Casilinum, through the midst of which flows a dividing river, called Vulturnus by the Romans.
The region is otherwise encompassed by mountains, but a narrow defile opens out towards the sea, in the vicinity of which it becomes marshy, from the overflow of the river, has high sand-heaps, and terminates in a beach where there is no anchorage because of the dashing waves. While Hannibal was descending into this valley, Fabius, taking advantage of his acquaintance with the ways, marched round him, and blocked up the narrow outlet with a detachment of four thousand heavy infantry. The rest of his army he posted to advantage on the remaining heights, while with the lightest and readiest of his troops he fell upon the enemy's rear-guard, threw their whole army into confusion, and slew about eight hundred of them.
Hannibal now perceived the mistake in his position, and its peril, and crucified the native guides who were responsible for it. He wished to effect a retreat, but despaired of dislodging his enemies by direct attack from the passes of which they were masters. All his men, moreover, were disheartened and fearful, thinking that they were surrounded on all sides by difficulties from which there was no escape. He therefore determined to cheat his enemies by a trick, the nature of which was as follows.
He gave orders to take about two thousand of the cattle which they had captured, fasten to each of their horns a torch consisting of a bundle of withes or faggots, and then, in the night, at a given signal, to light the torches and drive the cattle towards the passes, along the defiles guarded by the enemy. As soon as his orders had been obeyed, he decamped with the rest of his army, in the darkness which had now come, and led it slowly along.
The cattle, as long as the fire was slight, and consumed only the wood, went on quietly, as they were driven, towards the slopes of the mountains, and the shepherds and herdsmen who looked down from the heights were amazed at the flames gleaming on the tips of their horns. They thought an army was marching in close array by the light of many torches.
But when the horns had been burned down to the roots, and the live flesh felt the flames, and the cattle, at the pain, shook and tossed their heads, and so covered one another with quantities of fire, then they kept no order in their going, but, in terror and anguish, went dashing down the mountains, their foreheads and tails ablaze, and setting fire also to much of the forest through which they fled.
It was, of course, a fearful spectacle to the Romans guarding the passes. For the flames seemed to come from torches in the hands of men who were running hither and thither with them. They were therefore in great commotion and fear, believing that the enemy were advancing upon them from all quarters and surrounding them on every side. Therefore they had not the courage to hold their posts, but withdrew to the main body of their army on the heights, and abandoned the defiles. Instantly the light-armed troops of Hannibal came up and took possession of the passes, and the rest of his forces presently joined them without any fear, although heavily encumbered with much spoil.