The threat of invasion by Rome's former allies in Latium led to the appointment of Aulus Postumius Albus as dictator. The year in which the battle occurred is unclear, and has been unclear since ancient times. Livy places the battle in 499 BC, but says some of his sources also suggest the battle occurred during Postumius' consulship in 496 BC. The other major source for this historical period, Dionysius of Halicarnassus also places the battle in 496 BC. Modern authors have also suggested 493 BC or 489 BC. Lake Regillus was located in the remains of a volcanic crater between Rome and Tusculum. The lake was drained in the fourth century BC. According to Livy, the Volsci had raised troops to send to the aid of the Latins against Rome, however the haste of the Roman dictator in joining battle meant that the Volscian forces did not arrive in time.
Battle
The dictator Postumius led the Roman infantry, while Titus Aebutius Helva was Master of the Horse. Tarquin was accompanied by his eldest and last remaining son, Titus. It was said that the presence of the Tarquinii caused the Romans to fight more passionately than in any previous battle. Early in the battle, the king was injured attacking Postumius. The magister equitum charged at Mamilius, and both were wounded: Aebutius in the arm, and the Latin dictator in the chest. The magister equitum had to withdraw from the field and direct his troops from a distance. The king's soldiers, including many exiled Romans, began to overpower the republican forces, and the Romans suffered a setback when Marcus Valerius Volusus was killed by a spear while attacking Titus Tarquinius. However, Postumius brought in fresh troops from his own bodyguard and halted the exiles' progress. Meanwhile, Titus Herminius Aquilinus, who had won fame fighting alongside Horatius at the Sublician bridge, and served as consul in 506 BC, engaged Mamilius and slew him; but while attempting to strip his fallen enemy and claim the spoils, Herminius was killed by a javelin. As the outcome of the battle seemed in doubt, Postumius ordered the cavalry to dismount and attack on foot, forcing the Latins to retreat and capturing the Latin camp. Tarquin and the Latin army abandoned the field, resulting in a decisive Roman victory. Postumius returned to Rome with his army, and celebrated a triumph. A popular legend reported that the Dioscuri, Castor and Pollux, fought alongside the Romans, transfigured as two young horsemen. Postumius ordered a temple built in their honour in the Roman Forum, in the place where they had watered their horses. In the nineteenth century, the battle was celebrated in Thomas Macaulay'sLays of Ancient Rome.
