What size of battle is it for?
Interesting question.
The rules are scale and base agnostic as it is a unit vs. Unit game. Typically there are 5-8 units per side.
However, this book also has some expanded rules for Army "wings" so you could have three wings each with 5-8 units per side if you wish. This allows it to be multi-player or just for bigger battles too.
I hope that helps.