Maybe! There's a book coming from Eden called "Fields of Blood"
http://www.edenstudios.net/odyssey/7005.html
"Fields of Blood: The Book of War provides everything you need to rule a nation, raise an army, and assault your enemies on the battlefield. With rules governing anything from small keeps to vast nations, your character can now be a hero both in the dungeon and on the battlefield.
Fields of Blood: The Book of War is totally scalable to suit your campaign.
Inside you will find:
-A complete set of detailed wargame rules based on the d20 system mechanic to resolve combat at any scale.
-Rules for leading troops. Anything from a small squad of men to an army of thousands!
-Rules for governing. Everything from the cost of building and maintaining a small keep, to taxing a nation of millions.
-Rules for NPC nations allowing GMs to run several dozen opposing realms at a time.
-Leadership rules for every class, using your character's strengths to lead an army.
-Rules for using miniatures, or tracking the battles on a simple map.
-New prestige classes for every character type, designed for use with this system"
Not due out any time soon, I'm afraid.
