I've had a lot of games that in some point have had a war brewing in the background, coming into the fore in the later levels - when the PCs are the at levels to lead or otherwise have a dramatic effect on the battlefield.
I've used a variety of systems, some homebrew as well as the official rules for various versions (BECMI Warmachine, Battlesystem, Birthright's system, 3E's Miniature's handbook, 5E's mob rules, L5R cinematic rules, Warhammer Fantasy). I've never quite found a system that clicks with all players nor have quite satisfied me entirely.
I like the idea of a mass combat system and having a war-based story, but I've found over the years I'm a bad general when it comes to detailed systems/rank & file games. But, I find I need those detailed system to more accurately give me an idea of how the battle would go so I can design around the player's involvement and "wing it" without having to make them run with the same detail. If I could, I'd run the detailed minis game ahead of time with someone who'd be interested, and just run a "heroic intervention" variant for the players so it'd just hit the highlights