To the north of Alesia there was a hill (Mont Réa) which had not been enclosed in the lines, because it would have given them too great an extent; the camp necessary on that side had, for this reason, to be established on a slope, and in a disadvantageous position (_see Plate 25, camp D_); the lieutenants C. Antistius Reginus and C. Caninius Rebilus occupied it with two legions. The enemy’s chiefs resolved to attack this camp with one part of their troops, whilst the other should assail the circumvallation in the plain of Laumes. Having decided on this plan, they send their scouts to reconnoitre the localities, secretly arrange among themselves the plan and the means of execution, and decide that the attack shall take place at noon. They choose 60,000 men amongst the nations most renowned for their valour. Vercasivellaunus, one of the four chiefs, is placed at their head. They sally at the first watch, towards nightfall, proceed by the heights of Grignon and by Fain towards Mont Réa, arrive there at break of day, conceal themselves in the depressions of the ground to the north of that hill, and repose from the fatigues of the night. At the hour appointed, Vercasivellaunus descends the slopes and rushes upon the camp of Reginus and Rebilus; at the same moment, the cavalry of the army of succour approaches the retrenchments in the plain, and the other troops, sallying from their camps, move forwards. When, from the top of the citadel of Alesia, Vercingetorix saw these movements, he left the town, carrying with him the poles, the small covered galleries (_musculos_), the iron hooks (_falces_),[530] and everything which had been prepared for a sally, and proceeded towards the plain. An obstinate struggle follows;, everywhere the greatest efforts are made, and wherever the defence appears weakest, the Gauls rush to the attack. Scattered over extensive lines, the Romans defend only with difficulty several points at the same time, and are obliged to face two attacks from opposite sides. Fighting, as it were, back to back, everybody is agitated by the cries he hears, and by the thought that his safety depends upon those that are behind him; “it lies in human nature,” says Cæsar, “to be struck more deeply with the danger one cannot see.”[531]