The Battle of Arausio took place on 6 October 105 BC, at a site between the town of Arausio, now Orange, Vaucluse, and the Rhône river. Two Roman armies, commanded by proconsul Quintus Servilius Caepio and consul Gnaeus Mallius Maximus, clashed with the migratory tribes of the Cimbri under Boiorix and the Teutons under Teutobod.
Differences between the Roman commanders prevented regular coordination between their armies, resulting in annihilation by the united Cimbrian-Teutonic force. Roman losses are thought to have been up to 80,000 legionaries in addition to 40,000 auxiliary troops. Total losses numbered up to 120,000 soldiers, the entirety of both armies. In terms of losses, this battle is regarded as the worst defeat in the history of ancient Rome, surpassing the Battle of Cannae. According to classical historians, as a direct result of the catastrophe, the Roman military was supposedly restructured under Gaius Marius via putative reforms to the organisation and recruitment of Roman legions, which would remain principally intact for centuries thereafter. Some modern historians contest the existence of sudden reforms under Marius.
Prelude
The migrations of the Cimbri tribe through Gaul and adjacent territories had disturbed the balance of power and incited or provoked other tribes, such as the Helvetii, into conflict with the Romans. An ambush of Roman troops and the temporary rebellion of the town of Tolosa (modern Toulouse) caused Roman troops to mobilize in the area, with eighty strong forces.
Having regained Tolosa, the proconsul Quintus Servilius Caepio adopted a defensive strategy, waiting to see if the Cimbri would move toward Roman territories again. On 6 October 105 BC, they did.
Even before the battle had erupted, the Romans were in trouble. The senior of the year's two consuls, Publius Rutilius Rufus, was an experienced and highly decorated soldier, veteran of the recent war in Numidia, but he did not take charge of the military campaign himself but remained in Rome while his inexperienced, untried colleague Gnaeus Mallius Maximus led the legions north. The reasons for Rutilius not taking charge himself do not seem to be known: perhaps he faced political opposition because of his friendship with Gaius Marius, or perhaps he believed Mallius Maximus deserved the chance to earn himself a share of glory, or perhaps he was simply temporarily ill.
Two of the major Roman forces available were camped out on the Rhone River, near Arausio: one led by Mallius Maximus, and the other by the proconsul Quintus Servilius Caepio. As the consul of the year, Maximus out-ranked Caepio and therefore should by law have been the senior commander of the combined armies. However, because Maximus was a novus homo and therefore lacked the noble background of the Roman aristocracy – in addition to his military inexperience – Caepio refused to serve under him and made camp on the opposite side of the river.
Battle
The initial contact between the Romans and Cimbri occurred when a detached picketing group under the legate Marcus Aurelius Scaurus met an advance party of the Cimbri. The Roman force was completely overwhelmed and the legate was captured and brought before king Boiorix. Scaurus was not humbled by his capture and advised Boiorix to turn back before his people were destroyed by the Roman forces. The king of the Cimbri was indignant at this impudence and had Scaurus executed.
Caepio, however, only crossed the river after a direct order from the Senate, but even then insisted on having a separate camp and ignored orders from Mallius.
According to historian Theodor Mommsen, Caepio was presumably motivated into action by the thought that Maximus might be successful in negotiations and claim all the credit for a successful outcome; he launched a unilateral attack on the Cimbri camp on 6 October. However, Caepio's force was annihilated because of the hasty nature of the assault and the tenacity of Cimbri defence. The Cimbri were able to ransack Caepio's camp, which had been left practically undefended. Caepio himself escaped from the battle unhurt.