The Sack of Rome by the Gauls, 390 BCE

On July 18, 390 BC, at the Battle of the Allia, the Roman army was defeated by raiding Gauls leading to the sacking of Rome. An excerpt from the article:

"Prologue

In 391 BCE, Roman intervention broke the Gallic siege of the Etruscan city of Clusium. The next year, led by the Senones tribe and their chief Brennus, the infuriated Gauls went to war against Rome. The Roman army intercepted the Gauls on the banks of the Tiber, near its confluence with the Allia River, eleven miles (18 km) north of Rome. The Gallic charge shattered the Romans, who were utterly defeated. Now nothing seemed to stand in the way of the barbarians and the city of Rome.

Rome sacked and burnt

The day after the battle, as the sun set on July 19th, the Gallic army arrived at the walls of Rome. The gates were not shut and no troops manned the walls. The ease of their victory at the Allia and the undefended city, made the Gauls suspect a trap. For now, the Gallic army encamped between Rome and the nearby River Anio. Scouts rode off to reconnoiter the walls.

Inside Rome, the crying for the fallen was replaced by a silent terror. At night, the yelling enemy cavalry was heard outside the city walls, but no attack came. Most Romans considered their city doomed; the few remaining fighting men could never hold the walls, which were little more than an agger (earth rampart) protected by a ditch. The only hope was that the Citadel on the steep Capitol Hill could be defended. There the Senate and the men of military age, along with their families, sought refuge. The priests fled the city carrying their religious relics, alongside many of the plebs who cleared surrounding fields of anything edible.

Two days or so later, the Gauls entered the city unopposed. They were surprised that large numbers of people had already slipped through their fingers. Stationing a cordon of troops around the Capitol Hill, the Gallic army ransacked the city. The Gauls burnt and killed until the city was reduced to ruins and ashes. They then turned to finish off the defenders on the Capitol."