Between campaign battles

[Hrafnagudh]

So, I am enjoying the campaigns. I need some clarifications though, of what happens among battles.
1) how do garrison work? I understand that sometimes, not always, you are needed to letto some troops garrisoning a fortress. But otherwise, is there any reason to garrison? Leaving behind disheartened troops perhaps? Does garrisoning free up recruitment points for subsequent battles and allow to get Rif of weak troops?
2) troops that got broken have a chance to be disheartened next Battle. And troops that won may grow up in quality. Still, defensive spearmen for example, can just become superior defensive spear, but not "evolve" to offensive spear right?
3) Manpower of units. How does that work? Is the same number for all units with the same name and changes only with Battle losses or there is a little variability?
4) how do replenish dead troops work? Just take points to refill? In case of a badly battered troop, would it be wiser to leave them in garrison and recruit a fresh one?

[rbodleyscott]

So, I am enjoying the campaigns. I need some clarifications though, of what happens among battles.
1) how do garrison work? I understand that sometimes, not always, you are needed to letto some troops garrisoning a fortress. But otherwise, is there any reason to garrison? Leaving behind disheartened troops perhaps? Does garrisoning free up recruitment points for subsequent battles and allow to get Rid of weak troops?

Yes.

As troops go up in quality, they "get paid" (cost) more. So you can also use the garrison mechanic to pension off veterans whose expense might be deemed more than their worth - e.g. Superior/Elite light foot. You can then spend the freed up points on new, cheaper, units.

Also, if your whole army becomes Superior or Elite, it will get smaller (because the units cost more) and may have trouble avoiding being flanked by the enemy army of bog-standard troops. It is often more effective to have Superior/Elite troops as your strike force, and ordinary troops to keep the enemy off their flanks.

2) troops that got broken have a chance to be disheartened next Battle. And troops that won may grow up in quality. Still, defensive spearmen for example, can just become superior defensive spear, but not "evolve" to offensive spear right?

Correct

3) Manpower of units. How does that work? Is the same number for all units with the same name and changes only with Battle losses or there is a little variability?

There is some variability.

4) how do replenish dead troops work? Just take points to refill?

Yes

In case of a badly battered troop, would it be wiser to leave them in garrison and recruit a fresh one?

No need.