Hiya!
So how have you used wars in your campaigns? Did the characters participate? Was it happening during adventures? What worked? What didn't?

I'm a "bit odd" in what I enjoy about fantasy settings, sci-fi settings, horror settings, super hero settings, you get the picture. What I constantly think about and find the most interesting is... the common folk. I mean, the PC's are not "normal" 99% of the time in an RPG. They don't have "normal" lives and don't have to worry or even thinking about "normal" stuff that regular folks do. I mean, an adventurer gets zapped by a trap and he, and NONE of his equipment, finds himself teleported into the center of an old circle of Standing Stones in a deep forest! Now, "normal" people would loose their kittens and probably be dead in a matter of hours. The adventurer? He lets out a series of "strongly worded disappointments" then gets to gathering.
It is this dichotomy of "heroic protagonists / normal folks" that I love. In particular, how the simple fact that there ARE "Heroic Protagonists/Antagonists" in the normal persons world affects their day to day lives.
So...war. That's what I think about; how does it affect the farmer, his wife, and three daughters? How is a war going to affect the town's mill? Cooper? Stonemason? What about guardsmen for merchants who travel near, or through, potentially contested land? What about those guards family? How will their success, or death, affect them? Now...extrapolate to entire populations. How will the general population react to the war and the battles going on "hundreds of kilometers away"...then "dozens of kilometers away"....then "at our small towns palisade!"?
That's what I tend to play up. The people in the streets...not the King, not the Lords and Ladies, not the Knight Champions, the High Priest and his Contingent of Kord Berzerkers, nor Aerrithall, Master of the Arcane Staff of Power. They are important, sure, but they can all die and the only thing that will change for the peasants is the name of the person/people who are ultimately in control of their lives.
Focus on the PEOPLE and how war will/would affect them...and how far they are willing to be pushed. There is a limit to when the common folks just rise up and say "Nope. No more. We're outta here" and either wheel out the guillotine or pack up and hoof it.
^_^
Paul L. Ming