Concerned at the Ambrones and Cimbri rampaging so deep into Italy, the Senate had ordered Qunitus Caecilius Metellus’ recently-raised army of veterans and recruits to be stationed outside Rome. Thus deployed, they were available to protect the City, making use of the time for the veterans to work at turning the new recruits into soldiers worthy of the title of Roman legionaries.
Metellus had deployed his forces in parallel lines. Longinus' small force in front, his own veterans behind them and Saturninus' partially-tgrained recruits in the last line. Longinus' men were to absorb the initial Ambrones' onslaught, which would then be broken by Metellus' veterans. Saturninus men, the largest of all the commands, was in support, available to defend against any break-through.
Seeing the large Roman force before him, Boiroix sent forward his slingers and archers, whilst holding his warbands at a safe distance.
(A six of spades turned up meant that Longinus' legionaries were not at their best that day).
The Ambrones' skirmishers got the better of the initial combat 'tween the opposing light troops.
The Ambrones' cavalry attempted to outflank Longinus' line, but were themselves flanked by Metellus' Roman cavalry.
Metellus' plan seemed to be working as more of the Ambrone warbands reacted to the advance of Longinus' troops.
That six of spades proved prophetic as Longinus' legionaries were over-run in the first contact (in Impetus a six for determination of permanent losses is not a good result!).
Longinus' command broken, Metellus' veterans prepared to receive the still-fresh Ambrone warbands (the plan had not worked so well after all). Saturninus' men provided depth in support.
Pressure mounted on the Roman right flank as Metellus' Roman cavalry and Cretan archers were broken, ...
Thanks to the veterans that the senate had withdrawn from Spain and Africa, firstly the Teutones and now the Ambrones had been defeated. There still remained the Cimbri who, while this battle was occurring, were attacking Caepio at the Second Battle of Spoletium.