Titus Livius (Livy), The History of Rome, Book 5
Rev. Canon Roberts, Ed.

45. Friends¹ and foes were alike persuaded that nowhere else was there at that time so great a master of war. After the council broke up they refreshed themselves and waited eagerly for the signal to be given. When it was given in the silence of the night they were at the gates ready for Camillus. [2] After marching no great distance from the city they came upon the camp of the Gauls, unprotected, as he had said, and carelessly open on every side. [3] They raised a tremendous shout and rushed in; there was no battle, it was everywhere sheer massacre; the Gauls, defenceless and dissolved in sleep, were butchered as they lay. Those in the furthest part of the camp, however, startled from their lairs, and not knowing whence or what the attack was, fled in terror, and some actually rushed, unawares, amongst their assailants. [4] A considerable number were carried into the neighbourhood of Antium, where they were surrounded by the townsmen.

A similar slaughter of Etruscans took place in the district of Veii. So far were these people from feeling sympathy with a City which for almost four centuries had been their neighbour, and was now crushed by an enemy never seen or heard of before, that they chose that time for making forays into Roman territory, and after loading themselves with plunder, intended to attack Veii, the bulwark and only surviving hope of the Roman name. [5] The Roman soldiers at Veii had seen them dispersed through the fields, and afterwards, with their forces collected, driving their booty in front of them. [6] Their first feelings were those of despair, then indignation and rage took possession of them. ‘Are even the Etruscans,’ they exclaimed, ‘from whom we have diverted the arms of Gaul on to ourselves, to find amusement in our disasters?’ [7] With difficulty they restrained themselves from attacking them. Caedicius, a centurion whom they had placed in command, induced them to defer operations till nightfall. [8] The only thing lacking was a commander like Camillus, in all other respects the ordering of the attack and the success achieved were the same as if he had been present. Not content with this, they made some prisoners who had survived the night's massacre act as guides, and, led by them, surprised another body of Tuscans at the salt works and inflicted a still greater loss upon them. Exultant at this double victory they returned to Veii.