Mass combat in 3.5e tends to be a terribly overlooked part of the game. While it's expected for PCs to potentially join or own armies, the granularity of 3.5e has been set to skirmish-level events, meaning that larger battles become a monster of paperwork and bookkeeping. The fun part of armies, such as tactics on the battlefield, city-taking, and dragonkilling is so buried by the raw nature of individually statted out armies that any system except for the most abstract is just not fun….if you wanted to play Warhammer 40K, then you wouldn’t be playing 3.5e.