Achaeans at this time were at war with Machanidas the despot of Lacedaemon, who had immense resources at his disposal, and menaced the whole of Peloponnesus.  As soon as news came that he had invaded Arcadia and had reached Mantinea, Philopoemen with his army marched rapidly to attack him.  Both sides drew up their forces near the city of Mantinea, and both brought into the field not only nearly all their own countrymen, but also large bodies of foreign mercenary troops.  Machanidas began the battle by a charge of his mercenaries, who routed the Tarentines and other light troops of the Achaeans, but then instead of moving at once to attack and overwhelm their main body, hurried away in pursuit, leaving the Achaean phalanx standing untouched.  Philopoemen made light of the disaster which had happened to the light troops, and, perceiving the fault which the enemy had committed in leaving their heavy infantry unprotected, so that he had an open plain over which to march against them, disregarded those Lacedaemonians who were pursuing his own auxiliaries, and bore straight down upon their main body, which he took in flank, without any cavalry to protect it, or any general to give it orders, as the men did not expect to be attacked, and imagined that the victory was already won when they saw Machanidas so eager in the pursuit.  Philopoemen broke and routed them with great slaughter, four thousand men being said to have perished, and then turned to encounter Machanidas, who was returning with his mercenaries, and found his retreat cut off.  A deep and wide watercourse here divided the two leaders, the one of whom endeavoured to pass it and escape, while the other tried to prevent this.  They looked no longer like two generals, but the despot seemed more like some savage beast driven to bay by Philopoemen, that mighty hunter.  At length the despot spurred his horse, a fiery animal, to attempt the leap.  The horse gained the other bank with its fore feet, and was struggling up it, when Simias and Polyaenus, the constant companions and aides-de-camp of Philopoemen, rode to attack him with levelled lances.  Philopoemen, however, came up with Machanidas before them.  Seeing that the despot’s horse was rearing its head so as to protect its master’s body, he turned his own horse a little to one side, and, seizing his lance firmly with both hands, drove it through his body and cast him from his horse.  It is in this posture that Philopoemen is represented in the statue at Delphi, which was placed there by the Achaeans in token of their admiration of his courage and conduct on that day.