Extract from Design and Philosophy "War is Hell" section of the rules:
These rules are intended to cover actions of divisional size. In the main it is intended that players consider their forces to be of about 5 battalion strength.
These rules have been kept simple in mechanism in order to provide the players with an opportunity to explore tactics, scenarios and have some fun too. The player is in the position of overall commander. This means that the minutiae of detailed decisions are not always his concern (it would be bad generalship to keep checking subordinates for correct actions), thus the rules allow for unpredictable things to happen. These rules partition the figures and models into commands. A command represents a battalion sized formation.