The battle of the River Clusius (223 BC) was a Roman victory over the Insubres of northern Italy that was squandered by political infighting in Rome (Telamon War).
In 225 a Gallic alliance, led by the Boii and Insubres, had invaded Roman territory, getting dangerously close to Rome before eventually suffering a crushing defeat at the battle of Telamon. In the following year the consuls had conquered the Boii, who inhabited territory on the south bank of the Po, and may have crossed the Po, but without success. In 223 BC the consuls, C. Flaminius and P. Furius Philus, led a new invasion of Cisalpine Gaul, this time aiming to defeat the Insubres.
The location of this battle isn’t specified in the ancient sources. However the River Clusius is mentioned in Polybius’s account of the campaign leading up to the battle, and in a way that doesn’t entirely make sense. At the start of the campaign of 223 BC the Romans attempted to invade the Insubrian territory from the west, advancing through Ligurian territory to cross into the territory of the Anares, a friendly Gallic tribe that lived to the west of the Insubres. The Romans then crossed the Po at its junction with the Adda (between Piacenza and Cremona). They suffered losses while crossing the river, and when camped to the north of the Po, and were forced to agree a truce and return to the south bank.
After this setback the Romans moved east, along the south bank of the Po, presumably with the Insubres watching them from the north bank. According to Polybius they eventually crossed the River Clusius to enter the country of their allies, the Cenomani, who lived to the east of the Insubres. However the Clusius is on the northern bank of the Po, probably the modern Chiese, which flows south from the Alps and runs into the Oglio not far to the north of the Po. If the Romans had crossed this river to enter Cenomani country then they must have crossed the Po somewhere further west, in Insubrian territory, then marched east to join their allies. The two forces then combined and invaded Insubrian territory and began to lay waste to it. The Insubres quickly reacted, gathering 50,000 men and moved to a position facing the Romans, where the Romans had their backs to ‘the river’.
It is more likely that the Romans crossed the Po further east, when they were already in Cenomani country. The Romans and Cenomani then invaded Insubrian territory from the west, crossed the Clusius and began to lay waste to the country just across the river.
In either case the Insubres decided to gamble on the results of a decisive battle. They raised a force of about 50,000 men, took down their golden standards from the temple of Minerva, and moved to face the Romans.
The Romans now had a dilemma – without their Gallic allies they would be outnumbered, but they couldn’t entirely trust the Cenomani to fight against the Insubres. In the end the Romans decided not to take the risk, and sent the Cenomani back across the river, demolishing the bridges behind them. This had two purposes – first to stop the Cenomani attacking them from the rear, and secondly to force the Romans to fight more fiercely in the knowledge that they had no way to retreat. Flaminius was later criticised for deploying his men at the very edge of the river, denying his men the chance to carry out any tactical manoeuvres.
Polybius bases his account of the battle itself on an entirely false description of Gallic swords as being of such poor quality that after the first blows of the battle they would be so bent that they would be useless unless the men had the chance to put them on the ground to straighten them out. In order to take advantage of this, the Romans posted the spear armed triarii in the front line, instead of in their normal position as a reserve. Once the Gauls had worn their swords out in an attempt to slash at the spears, the Roman swordsmen would advance into melee, using their pointed shorter swords as a thrusting weapon. The Gauls were denied the space to slash with their swords and suffered very heavy losses.
Perhaps more significant is the comment that the Gauls were most effective in their initial attacks, when they were still fresh. The spear armed triarii were perhaps brought to the front to try and absorb the shock of the initial Gallic attack. Once the Gauls had lost some of their initial impetus, the sword armed Romans would attack, get in close and take advantage of their shorter swords.
One other possibility is that the Romans were actually attacked while they were crossing the river. In this version of the battle every available Roman would have rushed into battle, including the triarii, while their Gallic allies may have simply been trapped on the wrong side of the river when the battle began.
Polybius doesn’t give any casualties figures, although states that the Romans ‘slew the greater part of their adversaries’. Orosius gives casualty figures of 9,000 dead and 17,000 captured.
This battle was someone overshadowed by events back in Rome. Flaminius had been a controversial Tribune of the Plebs and had clashed with the Senate over the distribution of lands taken from the Gauls in earlier wars. Now his opponents began to claim that a series of bad omens seen in Rome meant that the consuls had been elected inauspiciously. The Senate sent letters summoning the two consuls back to Rome and ordering them not to engage in combat until the case had been judged. These letters arrived just before the battle against the Insubires, but the Consuls didn’t read them until after the fighting was over. After the battle the two consuls argued about what to do next, with Flaminius wanting to ignore the letter and continue the campaign, while Furius wanted to return home. In the end they stayed for a few days to pillage the area before returning to Rome. They were both awarded a Triumph, possibly against the will of the Senate.
By the time our historians were writing Flaminius’s reputation had been permanently blackened by his defeat and death by Hannibal at the battle of Lake Trasimene (217 BC), so some of the hostility to him in the later sources may have been influenced by this. Whatever was really behind this story, the controversy ended the campaign of 223 BC and meant that the Romans were unable to take advantage of their victory.