The Latin war which had been threatening for some years now at last broke out. A. Postumius, the Dictator, and T. Aebutius, Master of the Horse, advanced with a large force of infantry and cavalry to the Lake Regillus in the district of Tusculum and came upon the main army of the enemy. On hearing that the Tarquins were in the army of the Latins, the passions of the Romans were so roused that they determined to engage at once. The battle that followed was more obstinately and desperately fought than any previous ones had been. For the commanders not only took their part in directing the action, they fought personally against each other, and hardly one of the leaders in either army, with the exception of the Roman Dictator, left the field unwounded. Tarquinius Superbus, though now enfeebled by age, spurred his horse against Postumius, who in the front of the line was addressing and forming his men. He was struck in the side and carried off by a body of his followers into a place of safety. Similarly on the other wing Aebutius, Master of the Horse, directed his attack against Octavius Mamilius; the Tusculan leader saw him coming and rode at him full speed. So terrific was the shock that Aebutius' arm was pierced,: Mamilius was speared in the breast, and led off by the Latins into their second line. Aebutius, unable to hold a weapon with his wounded arm, retired from the fighting. The Latin leader, in no way deterred by his wound, infused fresh energy into the combat, for, seeing that his own men were wavering, he called up the cohort of Roman exiles, who were led by Lucius Tarquinius. The loss of country and fortune made them fight all the more desperately; for a short time they restored the battle, and the Romans who were opposed to them began to give ground.

XX. M. Valerius, the brother of Publicola, catching sight of the fiery young Tarquin conspicuous in the front line, dug spurs into his horse and made for him with levelled lance, eager to enhance the pride of his house, that the family who boasted of having expelled the Tarquins might have the glory of killing them. Tarquin evaded his foe by retiring behind his men. Valerius, riding headlong into the ranks of the exiles, was run through by a spear from behind. This did not check the horse's speed, and the Roman sank dying to the ground, his arms falling upon him. When the Dictator Postumius saw that one of his principal officers had fallen, and that the exiles were rushing on furiously in a compact mass whilst his men were shaken and giving ground, he ordered his own cohort--a picked force who formed his bodyguard--to treat any of their own side whom they saw in flight as enemy. Threatened in front and rear the Romans turned and faced the foe, and closed their ranks. The Dictator's cohort, fresh in mind and body, now came into action and attacked the exhausted exiles with great slaughter. Another single combat between the leaders took place; the Latin commander saw the cohort of exiles almost hemmed in by the Roman Dictator, and hurried to the front with some maniples of the reserves. T. Herminius saw them coming, and recognised Mamilius by his dress and arms. He attacked the enemies' commander much more fiercely than the Master of the Horse had previously done, so much so, in fact, that he killed him by a single spear-thrust through his side. Whilst despoiling the body he himself was struck by a javelin, and after being carried back to the camp, expired whilst his wound was being dressed. Then the Dictator hurried up to the cavalry and appealed to them to relieve the infantry, who were worn out with the struggle, by dismounting and fighting on foot. They obeyed, leaped from their horses, and protecting themselves with their targets, fought in front of the standards. The infantry recovered their courage at once when they saw the flower of the nobility fighting on equal terms and sharing the same dangers with themselves. At last the Latins were forced back, wavered, and finally broke their ranks. The cavalry had their horses brought up that they might commence the pursuit, the infantry followed. It is said that the Dictator, omitting nothing that could secure divine or human aid, vowed, during the battle, a temple to Castor and promised rewards to those who should be the first and second to enter the enemies' camp. Such was the ardour which the Romans displayed that in the same charge which routed the enemy they carried their camp.
Thus was the battle fought at Lake Regillus. The Dictator and the Master of the Horse returned in triumph to the City.