C. Julius Caesar, Gallic War

When the Gauls, whose bold resolutions had been reported to Caesar, saw the legions advance with a regular motion, drawn up in battle array; either from the danger of an engagement, or our sudden approach, or with the design of watching our movements, they drew up their forces before the camp, and did not quit the rising ground. Though Caesar wished to bring them to battle, yet being surprised to see so vast a host of the enemy, he encamped opposite to them, with a valley between them, deep rather than extensive. He ordered his camp to be fortified with a rampart twelve feet high, with breastworks built on it proportioned to its height and two trenches, each fifteen feet broad, with perpendicular sides to be sunk: likewise several turrets, three stories high, to be raised, with a communication to each other by galleries laid across and covered over; which should be guarded in front by small parapets of osiers; that the enemy might be repulsed by two rows of soldiers. The one of whom, being more secure from danger by their height might throw their darts with more daring and to a greater distance; the other which was nearer the enemy, being stationed on the rampart, would be protected by their galleries from darts falling on their heads. At the entrance he erected gates and turrets of a considerable height.