The Gauls had made an appearance in strength with a large alliance of
their tribes, numbering no less than
25,000 warriors plus. The greater numbers were in the centre and on the
left (76 x Irr Bb O, F, Shk/Msl [Jav]), but their best hopes were pinned on a
picked force with the C-in-C’s bodyguard on the right of centre (24 x Irr Bb S,
F, Shk/Msl [Jav]). These were supported by some 2,000 mounted noblemen (Irr Cv
O (S), Shk/Msl [Jav]) behind the extreme right plus a few chariots in between
their three commands. They also had some 2000 light slingers and javelinmen
mainly in front of the centre.
The Romans opposite them, heavily outnumbered, had two veteran legions (38 x Reg Sw O, Pro, H Shk/Msl [Pila]), with supporting Auxiliarii (18 x Reg Plt O, Pro, H, Shk/Msl [Jav]) and War Engines (2 x Reg WE Pro, Medium, Msl) plus some 1500 light archers and slingers (10 x Irr Sk O, Msl [Sling][Bow]), but only very little cavalry on the left (4 x Reg Cv O, Shk/Msl [Jav]). They did have the advantage of terrain, having chosen to protect their left opposite the picked opposition by difficult terrain and a couple of rough hills; their right was deployed behind a swamp and the War Engines were in the center.
The Gauls came on quickly trying to get to grips with the Roman legionnaires. In the centre, they advanced in good order supported by the picked troops on their right, but as soon as they came within range of the bolt shooters all hell broke loose. The light losses inflicted on them caused a riot and those tribal units hit charged pell-mell at the War Engines simply overruning their light screens, who were trying to cover the gaps in between. The Gallic chief did the only thing he could. He ordered a full attack all along the line to support them. The battle then developed into three separate clashes each of which was of different character, but with the same result.
In the center, the Gauls, taking some casualties, approached the Roman
battle line and their commander tried to restore their order in order to charge
properly, but the Romans promptly counter charged them, throwing pila and broke
two out of the three most advanced warbands even before they came into contact.
The third warband crashed disordered and unsupported into the Romans and was
gradually absorbed and exterminated. The reserves behind them seeing this
slaughter simply broke and ran.
On the Roman left, the picked warriors of the Gauls and the noble horsemen, assisted by the swift charioteers, had caught and destroyed the Romans’ allied slingers who were not very careful, but not before the Gallic cavalry had lost heavily in men and horses. Then, in truly barbarian style, the warriors ran ahead blocking the only good cavalry terrain. As it happened, this didn’t matter much in the end. The picked warriors crashed into the legionnaires with incredible force and destroyed an unfortunate cohort blocking their way, but on the day, Mars was on the Roman side and they were gradually beaten back and surrounded by the legionnaire supports. The Auxiliarii of the central command, taking advantage of the demise of the Gallic centre, swept behind them and the encirclement was complete. The slaughter commenced and none of the picked warriors survived, their leader amongst them.
Meanwhile, the depleted Gallic cavalry went
around the rough hills, met the Roman horse trying to parry their move, beat it
back and then broke and ran as it saw its C-in-C being run through in the
cauldron. The whole command had been almost annihilated. This was really not
their day.
On the Roman right, their four large warbands of 2,000+ warriors each,
were met, well ahead of the battle line, by a very effective screen of
skirmishers. Behind the skirmishers stood only three of cohortes of Auxiliarii,
well inside the swamps. The light troops caused mayhem on all the barbarian
units, who found themselves incapable of mounting a single coordinated charge.
First one, then the second, then the other two warbands charged at the archers
and slingers, throwing javelins, but were no match for the lighter troops. Each
lost a steady stream of men without catching the evading skirmishers and as
soon as the first of them reached the swamp their remnants were picked off
one–by-one by the Auxiliarii. The same happened with the second and then the
third, while the fourth one fled the field when they could take no more. The
Roman legionnaires behind the swamp were never used at all.
This was a complete disaster of a huge and proud army. Over 20,000 warriors
perished at the cost of approximately 500 legionnaires and auxiliarii plus
another 300 horsemen and slingers.