Whilst the barbarians were hastening with all speed, the military tribunes brought the Romans into the field to be ready to engage them, being not inferior to the Gauls in number (for they were no less than forty thousand foot), but most of them raw soldiers, and such as had never handled a weapon before. Besides, they had wholly neglected all religious usages, had not obtained favorable sacrifices, nor made inquiries of the prophets, natural in danger and before battle. No less did the multitude of commanders distract and confound their proceedings; frequently before, upon less occasions, they had chosen a single leader, with the title of dictator, being sensible of what great importance it is in critical times to have the solders united under one general with the entire and absolute control placed in his hands. Add to all, the remembrance of Camillus's treatment, which made it now seem a dangerous thing for officers to command without humoring their solders. In this condition they left the city, and encamped by the river Allia, about ten miles from Rome, and not far from the place where it falls into the Tiber; and here the Gauls came upon them, and, after a disgraceful resistance, devoid of order and discipline, they were miserably defeated. The left wing was immediately driven into the river, and there destroyed; the right had less damage by declining the shock, and from the low ground getting to the tops of the hills, from whence most of them afterwards dropped into the city; the rest, as many as escaped, the enemy being weary of the slaughter, stole by night to Veii, giving up Rome and all that was in it for lost.
This battle was fought about the summer solstice, the moon being at full, the very same day in which the sad disaster of the Fabii had happened, when three hundred of that name were at one time cut off by the Tuscans.
And now, after the battle, had the Gauls immediately pursued those that fled, there had been no remedy but Rome must have wholly been ruined, and all those who remained in it utterly destroyed; such was the terror that those who escaped the battle brought with them into the city, and with such distraction and confusion were they themselves in turn infected. But the Gauls, not imagining their victory to be so considerable, and overtaken with the present joy, fell to feasting and dividing the spoil, by which means they gave leisure to those who were for leaving the city to make their escape, and to those that remained, to anticipate and prepare for their coming.
On the third day after the battle, Brennus appeared with his army at the city, and, finding the gates wide open and no guards upon the walls, first began to suspect it was some design or stratagem, never dreaming that the Romans were in so desperate a condition.
But when he found it to be so indeed, he entered at the Colline gate, and took Rome, in the three hundred and sixtieth year, or a little more, after it was built.
Brennus having taken possession of Rome, set a strong guard about the Capitol, and, going himself down into the forum, was there struck with amazement at the sight of so many men sitting in such order and silence, observing that they neither rose at his coming, nor so much as changed color or countenance, but remained without fear or concern, leaning upon their staves, and sitting quietly, looking at each other. The Gauls, for a great while, stood wondering at the strangeness of the sight, not daring to approach or touch them, taking them for an assembly of superior beings. But when one, bolder than the rest, drew near to Marcus Papirius, and, putting forth his hand, gently touched his chin and stroked his long beard, Papirius with his staff struck him a severe blow on the head; upon which the barbarian drew his sword and slew him.
This was the introduction to the slaughter; for the rest, following his example, set upon them all and killed them, and dispatched all others that came in their way; and so went on to the sacking and pillaging of the houses, which they continued for many days ensuing.