Infantry Relief System

[M. Demetrius]

Macedon: it dictates that each man should be relieved whenever he had to.

Right. And we are sure that if "the best men" were to have been kept in the front line until they dropped, there would be a constant rotation (of sorts) of exactly who the best men were. Everyone, no matter how strong, experienced, or brave, will reach a point of fatigue beyond which they are ineffective.

Being in the front line at the start of a battle is not insurance that the same man will be in the front line at its finish. And these battles ebbed and flowed, like waves on a beach. As the enemy fell back to regroup and remove the wounded for care, someone who was overtired could be released to rest and water, bandages and catching his breath. What can a soldier do who charges when out of breath?