C. Julius Caesar, Gallic War

Caesar, in five days' march, went from that place to Gergovia , and after engaging in a slight cavalry skirmish that day, on viewing the situation of the city, which, being built on a very high mountain, was very difficult of access, he despaired of taking it by storm, and determined to take no measures with regard to besieging it before he should secure a supply of provisions. But Vercingetorix, having pitched his camp on the mountain near the town, placed the forces of each state separately and at small intervals around himself, and having occupied all the hills of that range as far as they commanded a view [of the Roman encampment], he presented a formidable appearance; he ordered the rulers of the states, whom he had selected as his council of war, to come to him daily at the dawn, whether any measure seemed to require deliberation or execution. Nor did he allow almost any day to pass without testing in a cavalry action, the archers being intermixed, what spirit and valor there was in each of his own men. There was a hill opposite the town, at the very foot of that mountain, strongly fortified and precipitous on every side (which if our men could gain, they seemed likely to exclude the enemy from a great share of their supply of water, and from free foraging; but this place was occupied by them with a weak garrison): however, Caesar set out from the camp in the silence of night, and dislodging the garrison before succor could come from the town, he got possession of the place and posted two legions there, and drew from the greater camp to the less a double trench twelve feet broad, so that the soldiers could even singly pass secure from any sudden attack of the enemy.