Charge! rules

 Charge! – or how to play War Games, by Brigadier Peter Young and Lieutenant Colonel James Philip Lawford

Originally published in 1967. I think if you used Prince August 40mms you should consider getting a set of the Charge! rules. Designed for large units of individually based figures.  Charge! Or How to Play War Games | Image | BoardGameGeek

Vintage Wargaming: Charge! or how to play wargames