Titus Livius (Livy), The History of Rome, Book 9
Rev. Canon Roberts, Ed.

27. The¹ rumour of these proceedings, and, still more, the expectation of a Campanian revolt, which had already been secretly organised, recalled the Samnites from their designs in Apulia. [2] They marched to Caudium, which from its proximity to Capua would make it easy for them, if the opportunity offered, to wrest that city from the Romans. [3] The consuls marched to Caudium with a strong force. For some time both armies remained in their positions on either side of the pass, as they could only reach each other by a most difficult route. [4] At length the Samnites descended by a short detour through open country into the flat district of Campania, and there for the first time they came within sight of each other's camp. [5] There were frequent skirmishes, in which the cavalry played a greater part than the infantry, and the Romans had no cause to be dissatisfied with these trials of strength, nor with the delay which was prolonging the war. [6] The Samnite generals, on the other hand, saw that these daily encounters involved daily losses, and that the prolongation of the war was sapping their strength. [7] They decided, therefore, to bring on an action. They posted their cavalry on the two flanks of their army with instructions to keep their attention on their camp, in case it were attacked, rather than on the battle, which would be safe in the hands of the infantry. [8] On the other side, the consul Sulpicius directed the right wing, Poetilius the left. The Roman right was drawn up in more open order than usual, as the Samnites opposed to them were standing in thinly extended ranks in order either to surround the enemy or to prevent themselves from being surrounded. [9] The left, which was in a much closer formation, was further strengthened by a rapid manoeuvre of Poetilius, who suddenly brought up into the fighting line the cohorts which were usually kept in reserve, in case the battle was prolonged. He then charged the enemy with his full strength. [10] As the Samnite infantry were shaken by the weight of the attack their cavalry came to their support, and riding obliquely between the two armies were met by the Roman cavalry who charged them at a hard gallop and threw infantry and cavalry alike into confusion, until they had forced back the whole line in this part of the field. [11] Sulpicius was taking his part with Poetilius in encouraging the men in this division, for on hearing the battleshout raised he had ridden across from his own division, which was not yet engaged. [12] Seeing that the victory was no longer doubtful here he rode back to his post with his 1200 cavalry, but he found a very different condition of things there, the Romans had been driven from their ground and the victorious enemy were pressing them hard. [13] The presence of the consul produced a sudden and complete change, the courage of the men revived at the sight of their general, and the cavalry whom he had brought up rendered an assistance out of all proportion to their numbers, whilst the sound, followed soon by the sight of the success on the other wing, re-animated the combatants to redouble their exertions. [14] From this moment the Romans were victorious along the whole line, and the Samnites abandoning all further resistance, were all killed or taken prisoners, with the exception of those who succeeded in escaping to Maleventum, now called Beneventum Their loss in prisoners and slain is stated by the chroniclers to have amounted to 30,000.