The Battle of the Allia was fought c. 387 BC between the Senones – a Gallic tribe led by Brennus, who had invaded Northern Italy – and the Roman Republic.
The battle was fought at the confluence of the Tiber river and Allia brook, 11 Roman miles (16 km, 10 mi) north of Rome. The Romans were routed and subsequently Rome was sacked by the Senones.
The dies Alliensis ('Day of the Allia') was regarded as an ill-omened day in the Roman calendar, and treated as a dies religiosus on which public and ritual activity was avoided. Although later authors such as Livy present it as a lasting civic taboo, the tradition is only attested from the 1st century BC and likely reflects later reconstruction rather than continuous observance from the 4th to the 1st century AD.
Background
The Senones were one of the various Gallic tribes that had recently invaded northern Italy. They settled on the Adriatic Coast around what is now Rimini. According to Livy, they were called to the Etruscan town of Clusium (now Chiusi, Tuscany) by Aruns, an influential young man of the city who wanted to take revenge against Lucumo, whose son had "debauched his wife". When the Senones appeared, the Clusians felt threatened and asked Rome for help. The Romans sent the three sons of Marcus Fabius Ambustus, one of Rome's most powerful aristocrats, as ambassadors. They told the Gauls not to attack Clusium and that if they did, the Romans would fight to defend the town. They then asked to negotiate peace. The Senones accepted peace if the Clusians would give them some land. There was a quarrel and a battle broke out. The Roman ambassadors joined in, and one of them killed a Senone chieftain—violating the rule that ambassadors had to remain neutral. The brothers had taken sides and one of them had also killed a Senone. The Gauls withdrew to discuss what action to take.
According to Dionysius of Halicarnassus, Lucumo was the king of the city. He assigned the guardianship of his son to Aruns before he died. When the son became a young man, he fell in love with the wife of Aruns and seduced her. The grieving Aruns went to Gaul to sell wine, olives, and figs. The Gauls had never seen such products and asked Aruns where they were produced. He replied that they came from a large and fertile land, inhabited by only a few people who were not good fighters. He advised them to drive the people out of their land and enjoy the fruit as their own. He persuaded them to come to Italy, go to Clusium, and make war. Dionysius' account presumes that those Gauls had not invaded Italy and were in Gaul. When Quintus Fabius, one of the Roman ambassadors, killed a Gallic leader, they wanted the brothers to be handed over to them to pay the penalty for the men they had killed.
When the ambassadors of the Senones arrived in Rome and demanded the three Fabii brothers be handed over to them, the Senate was pressured by favouritism not to express opinions against the powerful Fabia family. To avoid being blamed for a possible defeat if the Gauls attacked, they referred the matter to the people. Livy wrote that "those whose punishment they were asked to decide were elected military tribunes with consular powers [heads of state] for the coming year." The Gauls were enraged that those who had violated the law of nations had been honoured and marched on Rome, 130 km (81 mi) from Clusium. Livy wrote that "in response to the tumult caused by their swift advance, terrified cities rushed to arms and the country folk fled, but the Gauls signified by their shouts wherever they went that their destination was Rome."
Chronology and estimates of forces
Date of the battle
The date of the battle has been traditionally given as 390 BC in the Varronian chronology, based on an account of the battle by the Roman historian Livy. Plutarch noted that the battle took place "just after the summer solstice when the moon was near the full [...] a little more than three hundred and sixty years from the founding [of Rome]", or shortly after 393 BC. The Greek historian Polybius used a Greek dating system to derive the battle as having taken place in 387 BC. Modern historians consider c. 387 BC to be the most probable date.
Tacitus listed the date as 18 July. Others ancient sources write that 16 July was also considered ill-omened because of the disaster. Modern scholars have noted that 18 July coincides with the date given for the Battle of the Cremera (477 BC), suggesting that early roman historians such as Fabius Pictor (born c. 270 BC) may have aligned the Battle of the Allia with the earlier sacrifice of the Fabii. Plutarch uniquely dates the battle to the full moon following the summer solstice, which suggests the events actually occurred around 15 July in the archaic lunar-solar calendar.
Troop numbers
None of the ancient sources produce reliable estimates for the number of men at the battle. They record forces for each side ranging from 24,000 to 40,000. Modern estimates, however, are usually lower. Jeremy Armstrong suggests that both sides had around 5,000 men, which would be realistic for a Gallic mercenary band and the small size of Rome during this period. Other modern historians, such as Max Cary and H. H. Scullard, instead placed the Romans with some 15,000 men against a huge Gallic army of between thirty and seventy thousand. Peter Berresford Ellis gives an estimate of a minimum of 24,000 based on the assumption that "the Romans had ... four legions – for each consul had two legions under his command – and given that each legion had 6,000 men". He also thinks that there may have been a contingent of allied troops, and that the Senones tribal army could "scarcely number more than 12,000".
Battle
There are only two ancient accounts that provide details of the battle. One is by Livy, and the other by Diodorus Siculus.
According to Livy, no special measures were taken in Rome, and the levy "was not larger than had been usual in ordinary campaigns". The Gauls marched on Rome so quickly that "Rome was thunderstruck by the swiftness at which they moved, which is shown both by the haste in mustering the army as if it were meeting a spur-of-the-moment emergency and the difficulty in getting any further than the eleventh milestone." At the eastern juncture of the Tiber River and Allia brook, the parties met; the Romans presumably were outnumbered. They did not set up camp or build a defensive rampart and they did not divine the gods, as they were supposed to. They extended the wings to avoid being outflanked, but that made their line so thin and weakened that the centre could hardly be kept together. They placed the reserves on a hill on the right. Brennus, the Senone chieftain, suspected that to be a ruse and that the reservists would attack him from the rear while he was fighting the Roman army on the plain. He, therefore, attacked the hill.
The Romans panicked. The left-wing threw their arms down and fled to the bank of the River Tiber. The Gauls killed the soldiers who were blocking one another's paths in the disorderly flight. Those who could not swim or were weak were weighed down by their armour and drowned. Still, the majority of the men reached Veii, an Etruscan city that had recently been conquered by Rome and was near the other bank. They did not even send a messenger to warn Rome. The right-wing, further from the river and closer to the hill, fled to Rome. The Gauls were surprised at how easy their victory had been.
The ancient Greek historian Diodorus Siculus said the Romans marched and crossed the River Tiber. He is the only ancient historian who placed the battle on the right bank of the river. The Romans lined up their best troops, 24,000 men, on the plain and placed the weakest troops on the hill. The Celts also lined up, placed their best men on the hill, and easily won the clash. The bulk of the Roman soldiers on the plain fled to the river in a disorderly manner and impeded each other. The Celts killed the men in the rear. Some Romans tried to cross the river wearing their armour, which, according to Diodorus, they prized more than their lives, but that weighed them down. Some drowned and some managed to reach the bank further downstream with great effort. As the Gauls kept killing the Romans, the soldiers then threw their arms away and swam across the river. The Gauls threw javelins at them. Most of the survivors fled to the city of Veii. Some returned to Rome and reported that the army had been destroyed.
Plutarch wrote that the Gauls encamped near the confluence of the Allia with the Tiber, some 18 km (11 mi) from Rome, and attacked the Romans suddenly. There was a "disorderly and shameful battle". The Roman left wing was pushed into the river and destroyed while the right-wing withdrew before the Gauls' attack from the plain to the hills and most of them fled to Rome. The rest of the survivors escaped to Veii at night. "They thought that Rome was lost and all her people slain."
Sack of Rome
Account of Livy
Livy provides a detailed account of the sack of Rome. The Gauls were dumbfounded by their sudden and extraordinary victory and did not move from the place of the battle, as if they were puzzled. They feared a surprise and despoiled the dead, as was customary for them. When they did not see any hostile action, they set off and reached Rome before sunset. They saw that the city gates were open and that the walls were unmanned. That was another surprise. They decided to avoid a night battle in an unknown town and encamped between Rome and the River Anio. The inhabitants of Rome were in panic and did not know that most of their soldiers had fled to Veii, instead of Rome, and thought that the only survivors were those who fled back to Rome and that they had only a tiny force. Realising that they were defenceless, they decided to send the men of military age, the able-bodied senators and their families to the Capitoline Hill with weapons and provisions to defend the fortress. The Flamen of Quirinus and the Vestal Virgins, who were priests, were to take "the sacred things of the State" away and continue to perform their sacred cults. The situation was so dire that the elderly were left behind in the city and former consuls stayed with them to reconcile them with their fate. However, many of them followed their sons to the Capitoline. No one had the heart to stop them. Many people fled to the Janiculum Hill just outside the city and then dispersed to the countryside and other towns. The Flamen of Quirinus and the Vestal Virgins could take only some of the sacred objects and decided to bury the rest under the chapel next to the Flamen's house. They set off to the Janiculum with what they could carry. Lucius Albinus, who was leaving the city on a wagon, saw them walking. He ordered his wife and children to get off and gave them and the sacred vessels of Rome a lift to Caere, an Etruscan city on the coast that was an ally of Rome.
Those who had been officers of state decided to meet their fate wearing their ceremonial dresses and "the insignia of their former rank and honour and distinctions". They sat on their ivory chairs in front of their houses. The next day, the Senones entered the city. They passed through the open Colline Gate and went to the Roman Forum. They left a small body to guard there against any attack from the Capitoline and went through the streets for plunder. They did not meet anybody. People moved to other houses. The Gauls returned to the area of the Forum. Livy memorably described Gauls' encounter with the elderly patricians:
The houses of the plebeians were barricaded, the halls of the patricians stood open, but they felt greater hesitation about entering the open houses than those which were closed. They gazed with feelings of real veneration upon the men who were seated in the porticoes of their mansions, not only because of the superhuman magnificence of their apparel and their whole bearing and demeanour but also because of the majestic expression of their countenances, wearing the very aspect of gods. So they stood, gazing at them as if they were statues, till, as it is asserted, one of the patricians, M. Papirius, roused the passion of a Gaul, who began to stroke his beard – which in those days was universally worn long – by smiting him on the head with his ivory staff. He was the first to be killed, the others were butchered in their chairs. After this slaughter of the magnates, no living being was thenceforth spared; the houses were rifled, and then set on fire.