C. Julius Caesar, Gallic War

The Gauls, confiding in the natural strength of their position, though they would not decline an engagement if the Romans attempted to ascend the hill, yet dared not divide their forces into small parties, lest they should be thrown into disorder by being dispersed, and therefore remained in order of battle. Caesar, perceiving that they persisted in their resolution, kept twenty cohorts in battle array, and, measuring out ground there for a camp, ordered it to be fortified. Having completed his works, he drew up his legions before the rampart and stationed the cavalry in certain positions, with their horses bridled. When the Bellovaci saw the Romans prepared to pursue them, and that they could not wait the whole night, or continue longer in the same place without provisions, they formed the following plan to secure a retreat. They handed to one another the bundles of straw and sticks on which they sat (for it is the custom of the Gauls to sit when drawn up in order of battle, as has been asserted in former commentaries), of which they had great plenty in their camp, and piled them in the front of their line; and at the close of the day, on a certain signal, set them all on fire at one and the same time. The continued blaze soon screened all their forces from the sight of the Romans, which no sooner happened than the barbarians fled with the greatest precipitation.