I'll have to disagree with Vaxalon and suggest that Cry Havoc is EXACTLY what you asked for.
It contains three scales, all interrelated with one another.
1) personal scale, which is the D&D rules you already know
2) unit scale, which lets you pit units of 100 - 200 creatures on a side against each other, using a 5:1 or 10:1 ratio, complete with "hero challenges" (like when 2 enemy commanders meet on the battlefield), and rules for leaderless units
3) finally, it contains Army Rules for engagements of hundreds to thousands of troops. The third level is more number crunch heavy, but contains complete rules for computing the strength of each side, and a heavy amount of cutomiation of the resolution, where the entire war can be decided in a couple of die rolls, or you can even a month-by-month or day-by-day evaluation of the war.
I demoed it at Gencon (by Skip Himself

) , and it's pretty sweet!
...Er, excuse me, "it highly objectifies in my opinion the kind of system you described."
My fanboyishness will now return to normal levels.