After the fortune of the fight has been restored, and the enemies driven back, he proceeds towards the place where he had sent Labienus, draws four cohorts from the nearest redoubt, orders a part of the cavalry to follow him, and the other part to go round by the exterior lines, to take the enemy in the rear by issuing from the camp of Grésigny. On his side, Labienus, seeing that neither the fosses nor the ramparts can arrest the efforts of the Gauls, rallies thirty-nine cohorts which have arrived from the neighbouring redoubts, and which chance offers to him, and informs Cæsar that, according to what had been agreed, he is going to make a sally.[532] Cæsar hastens his march in order to share in the combat. As soon as, from the heights on which they stood, the legionaries recognise their general by the colour of the garment which he was in the habit of wearing in battle (the purple-coloured _paludamentum_),[533] and see him followed by cohorts and detachments of cavalry, they sally from the retrenchments and begin the attack. Shouts arise on both sides, and are repeated from the _vallum_ to the other works. When Cæsar arrives, he sees the lines abandoned, and the battle raging in the plain of Grésigny, on the banks of the Ose. The Roman soldiers throw away the _pilum_, and draw their swords. At the same time, the cavalry of the camp of Grésigny appears in the rear of the enemy; other cohorts approach. The Gauls are put to the rout, and in their flight encounter the cavalry, who make great slaughter among them. Sedulius, chief and prince of the Lemovices, is slain; the Arvernan Vercasivellaunus is taken prisoner. Seventy-four ensigns are brought to Cæsar. Of all this army, so numerous as it was, few combatants return to their camp safe and sound. Witnesses, from the top of their walls, of this sanguinary defeat, the besieged despaired of their safety, and called in the troops who were attacking the countervallation.[534] As the result of these reverses, the Gauls of the army of succour fly from their camp; and if the Romans, compelled to defend so many points at one time, and to assist each other mutually, had not been worn out by the labours of a whole day, the entire mass of the enemies might have been annihilated. Towards the middle of the night the cavalry sent in pursuit came up with their rear-guard; a great part of them were taken prisoners or killed; the others dispersed, to return to their countries.