In the later chapters of a future campaign I'm thinking of having a section where the players take charge of parts of an army and fight a larger battle. I don't want to hand-wave the strategy, I want success or failure to be in the hands of the players. Are there any good rules for handling this in 3.5 or Pathfinder, either house rules or in supplements?
Clarification
Not that any of the answers are wrong, but I felt I should clarify that we don't generally use miniatures in our group (mostly because the table is too full of coffee, tea, sugar, milk, sweets, biscuits, pencils, dice and other randomness).
