Simple mass combat system?

[Dire Reverend]

Is there a mass-combat game out there that is somewhat simple?

I am pretty much looking for a pen and paper version of Advance Wars, if it exists.

[Knaight]

Your goals are in conflict with eachother - pick one, and this can be resolved more easily, particularly if we get information regarding the setting you want this for. With that said, Wargame Vault has a whole host of free wargames, many of which should be easy to use alongside RPGs with simple stat conversion. You might want to look into that, and if it doesn't work there is always this (http://www.freewargamesrules.co.uk/) option.

[Skarpskytten]

Book of Battle for Pendragon might do it. Lot's of rules, but I think it can be stripped down easily to the core concepts.