When he saw that the chance of smiting the enemy that had so long been present to his mind had at length arrived, Philopoemen ordered the whole phalanx to level their spears and charge.
When the Achaeans, like one man and with a loud cheer that cast terror into their foes, rushed on them, those of the Lacedaemonians who had broken their ranks and descended into the ditch, lost courage as they mounted the bank to meet the enemy above their heads and took to flight.
The greater number of them perished in the ditch itself, killed either by the Achaeans or by each other.
And this result was not due to chance or to momentary luck, but to the sagacity of the commander in at once protecting his men by the ditch.
This he did not with the desire to avoid an encounter as was supposed by some, but calculating everything accurately like the expert general he was and foreseeing that if Machanidas, when he came up, led his force forward without reckoning on the ditch, the phalanx would suffer what I have just described as actually happening to it, whereas if the tyrant took into consideration the difficulty presented by the ditch, and changing his mind, seemed to shirk an encounter, breaking up his formation and exposing himself in long marching order, he would then without a general engagement himself secure victory while Machanidas would suffer defeat.
This has already happened to many, who after drawing up in order of battle, being under the impression that they were not equal to engaging the enemy, either owing to their position
or owing to their inferiority in numbers or for any other reason, have exposed themselves in a long marching column, hoping as they retired to succeed, by the sole aid of their rearguard, either in great the better of the enemy or in making further their escape.
This is a most frequent cause of error on the part of commanders.
Walbank Commentary