Brennus, the Battle of Allia and the First Sack of Rome

Oct 6, 2011
Ivan Castro

Gaul Warriors - 19th Century Engraving - Eon Images - Public Domain

In 390 or 387 BC a large contingent of Gauls (Celt) defeated a smaller Roman force by the Allia River and opened the door to the first sack of Rome.

Under the leadership of Brennus, a chieftain of the Senones tribe, some 30,000 Gauls warriors overran the Roman defenses manned by anywhere 10,000 to 15,000 men. Some sources estimate that the battle was even bigger, just about doubling the size of the opposing armies.

Events Leading up to the Battle

In search of new territories the Senones had migrated across the Apennine Mountains into Etruria, roughly today’s Tuscany. In due course they settle near Clusium and embarked in negotiations with the locals over the acquisition of land. The town’s dwellers, however, didn’t trust the newcomers and sent for Roman help.

Rome, at the time a republic, was not only badly prepared, but exhausted from recent battles would only sent a peace delegation headed by three brothers from the Fabbi, a powerful patrician family.

Not waiting on their protectors, the authorities of Clusium dispatched a force to expel the Gauls. In the middle of the escalation, and in violation of all diplomatic treaty a courtesy, the Fabbi brothers got into a brawl with some Senone leaders, killing one.

The main Gaul chieftain, Brennus, removed his troops from the field, and demanded that the brothers be returned to face execution. While a good number of Roman authorities were willing to turn over the Fabians, the populace was not. The citizens of Rome pressured the government into treating the Fabians as heroes and they were appointed tribunes, a mid to high ranking military officer.

Naturally offended, the Senones pledge to make war on Rome.

March on Rome

Seeking revenge, the Gauls started a 60-mile march towards Rome. On their way, they made sure that the dwellers of towns and settlements they passed understood that their fight was with Rome and not them. Not a single field was burned and they treated everybody as a friend.

The Celtic host finally came face to face with the Romans some eight miles north of the Eternal City on the margins of the river Allia, a tributary of the Tiber.

At this time, Rome was still a Republic and its armed forces were not as well organized. Legions seldom were at full strength and citizen soldiers had to be added to the defensive line. The rich and, supposedly better armed and trained, soldiers were at the center of the formation. The new conscripts, usually ill trained and poorly equipped manned the flanks.

The Battle

No fool, Brennus decided to attack the flanks. It was no contest. The flanks were quickly beaten. Soldiers in the right side quickly ran back to Rome and those in the left fled to the small town of Veii.

With the sides disposed off, the Gauls surrounded the Roman center. It was a bloodbath, the worse defeat suffered by Rome to that date.

What was left of the Roman forces and many civilians took refuge on the Capitoline Hill. There they would hold off the invading Celts, causing enormous looses.

But the rest of the city was open to the invaders. The Celtic warriors proceeded to occupy and sack Rome for seven months. Not only did they take immeasurable riches, but they destroyed most of the precious records the Romans kept.

Consequences of Allia

Even though they won the battle and pillaged the city, the Gauls could not keep Rome. Their lack of hygiene and poor disposal of the dead bodies that littered the city caused serious epidemics. The frontal tactics they used to dislodge the locals from the Capitoline Hill also exposed their deficiency in military tactics.

Eventually, a Roman army under the command of Marcus Furius Camillus retook the city and saved the 1,000 pounds of gold the authorities had agreed to pay to Brennus to abandon the city.

Rome got a new and improved defense, the Servian Wall.

The idea of establishing a professional army took root among the Roman elite. Furthermore, iron-working techniques used by the Celts to make strong weapons were copied. The Romans would also copy and improve on their enemy’s large shields, which protected most of the body. These changes were the beginning of a restructuring that would guide the Roman military machine for the next 200 years and lead to its great conquests.

The government and citizens of the city also resolved that Rome would stay the capital of the realm. Foreigners would not enter Rome as conquerors again until 410 AD.

Sources