Allia

A powerful Celtic leader named Brennus marched his army of the Senones tribe right down into Italy.

Did they attack the city of Rome itself? They really did! Brennus absolutely crushed the Roman army at the River Allia.

The Roman citizens were so panicked that they actually abandoned the main streets of their own city and hid inside a fortress on a steep hill called the Capitol.

They just hid up there.

Modern historians have put the realistic size of each force at something like five thousand men each, with the Gauls likely bringing along a substantial number of camp followers.

The Romans met them on July eighteenth at the Allia, a small stream that drains the Crustumerian Hills into the Tiber about ten miles north of the city.

Livy says the Romans had no fortified camp and no experience of the Gallic style of fighting, which involved a great deal of skirmishing and cavalry harassment.

While Livy didn't mention this, it's important to remember that at this point, Rome was just one small city-state amongst many, and they controlled less than one percent of Italy at this point.

Moreover, their unfair treatment of Camillus was in no slight degree fatal to discipline, since it was now dangerous to hold command without paying regard to the pleasure and caprice of the people.

They advanced from the city about eleven miles, and encamped along the river Allia, not far from its confluence with the Tiber.

There the barbarians came suddenly upon them, and after a disorderly and shameful struggle they were routed.

Their left wing was at once driven into the river by the Gauls, and destroyed; their right wing was less cut up, because it withdrew before the enemy's onset from the plain to the hills, from which most of them made their way back to the city.

But most were still mastered by sleep and wine when they were fallen upon and slain without their arms.

A few only ran from the camp under cover of darkness, and when they came, were seen straggling about the fields, but horsemen pursued them and cut them to pieces.

Rumour quickly carried news of this exploit to the neighbouring cities, and called to arms many of those who were of age for service, particularly the Romans who had made their escape from the battle on the Allia and were in Veii.

These lamented among themselves, saying, Oh, what a leader has heaven robbed Rome in Camillus, only to adorn Ardea with his victories! The city which bore and reared such a hero is dead and gone, and we, for lack of generals, sit pent up within alien walls, and see Italy ruined before our very eyes.