If you have a solo unit of just one character, what happens when it is routed/destroyed? Does the sole member just retreat with low health?
Maybe it's just my inexperience on the forums, but... What?
I say that, actually wanting to understand.
I'm talking about the Mass Combat rules, as presented in Ultimate Campaign .
The rules are a little silent on the matter, so I would suggest just using the standard rules for defeat, coupled with the rules for defeating an army with a commander (since the fine army's commander is, by default, that same character).
For routing, assuming you're interested in what happens at character scale rather than mass combat scale, give them the frightened condition, which most closely models the effects, which will last until a successful Loyalty check made during the kingdom's next upkeep phase.
generals can escape, and be hurt and stuff or just captured... it depends.
It just seems a little busted - a wizard can be a solo unit, do some damage due to his spellcaster ability, but within the confines of mass combat he can't be harmed, really, just reduced to a set percentage of HP.
If an army is destroyed and the commander is an NPC, the commander is killed (01—20), captured (21—70), or escapes (71—00).
If you are the commander and your army is destroyed, the GM should present you with an opportunity to escape with serious injuries (at 25% hp or lower), otherwise you are captured and held for ransom.
Basically, PCs get a chance to escape with serious damage, or get captured. NPCs are captured half the time, but might escape, or might be killed.
These parts of the rules need a fair bit of GM adjudication and effort to make them work right.