Sextus Iulius Frontinus, vir consularis de re militari

The same man, when the enemy pressed upon his rear during a march, and while a river intervened—not so large as to prevent transit, yet slowing them down by its velocity—placed another legion in hiding on this side of the river so that the enemy, despising their fewness, would follow more boldly. When this was done, the legion which had been disposed for this purpose attacked the enemy from an ambush and devastated them. Iphicrates, in Thrace, when he was leading his column along a long path due to the condition of the terrain, and it was reported to him that the enemy was about to attack the summit, ordered his cohorts to turn aside and stop on both sides, while the others fled and hastened the journey. When the entire column had passed, he retained those chosen men, and thus, having attacked the enemy, who were scattered and occupied with plunder and already fatigued, he routed them and reclaimed the booty. The Boii, in the Litana forest where our army was about to pass, had cut the trees in such a way that, held up by a small part, they stood until they were pushed. Then, when the enemy had entered the forest and approached the outermost trees, they themselves pushed the ones further on, and in that way, with the collapse falling upon the Romans, they destroyed them with a large force.

How those things in which we are lacking may appear not to be missing, so that their utility is fulfilled. Chap. vii.

Veius Cecilius Metellus, because the supply of ships in which he could transport elephants was lacking, bound together casks and constructed boards, and having placed the elephants upon them, sent them across the Sicilian strait. Hannibal, when he could not force the elephants across a deep river and lacked a supply of ships or materials with which to hold rafts together, ordered the most fierce elephant to be wounded behind the ear, and the one who had wounded it to swim across the river immediately and run away. The elephant, exasperated, swam across the river to pursue the author of his pain, and provided the example for the others to dare the same. The Carthaginian generals, about to equip their fleet, because they were lacking in spartum esparto grass/broom fiber, used the hair of their women to make ropes. The Massilians and Rhodians did the same. Marcus Antonius, fleeing from Mutina, gave tree bark to his soldiers instead of shields. Spartacus and his forces had shields made of wicker, which were covered with hides. I do not think this place is alien to recount that noble deed of Alexander the Macedonian, who, when afflicted with the most severe thirst with his army through the deserts of Africa, poured out the water offered to him by a soldier, with everyone watching, being more useful through the example of temperance than if he had wanted to share it.

On distinguishing the enemy. Chap. viii.