The day on which Vercingetorix arrived on the heights of Sacquenay,[516] Cæsar, as we have seen, encamped on the Vingeanne, near Longeau. Ignorant of the presence of the Gauls, he started next day, in marching column, the legions at a great distance from each other, separated by their baggage. When his vanguard arrived near Dommarien, it could perceive the hostile army. Vercingetorix was watching the moment they (the Romans) debouched, to attack. He had divided his cavalry in three bodies, and his infantry had descended from the heights of Sacquenay in order to take a position along the Vingeanne and the Badin. (_See Plate 24._) As soon as the vanguard of the enemy appears, Vercingetorix bars its way with one of the bodies of cavalry, while the two others show themselves in order of battle on the two wings of the Romans. Taken unexpectedly, Cæsar divides his cavalry also into three bodies, and opposes them to the enemy. The combat engages on all sides; the column of the Roman army halts; the legions are brought into line, and the baggage placed in the intervals. This order, in which the legions were, no doubt, in column of three deep, was easy to execute, and presented the advantages of a square. Wherever the cavalry gives way or is too hotly pressed, Cæsar sends to its support the cohorts, which he draws from the main body to range them in order of battle.[517] By this manœuvre he renders the attacks less vigorous, and increases the confidence of the Romans, who are assured of support. Finally, the German auxiliaries, having gained, to the right of the Roman army, the summit of a height (the hill of Montsaugeon), drive the enemies from it, and pursue the fugitives as far as the river, where Vercingetorix stood with his infantry. At the sight of this rout, the rest of the Gaulish cavalry fear to be surrounded, and take to flight. From this time the battle became a mere carnage. Three Ædui of distinction are taken and brought to Cæsar: Cotus, chief of the cavalry, who, at the last election, had contended with Convictolitavis for the sovereign magistracy; Cavarillus, who, since the defection of Litavicus, commanded the infantry; and Eporedorix, whom the Ædui had for chief in their war against the Sequani, before the arrival of Cæsar in Gaul.[518] [Sidenote: Blockade of Alesia.]