Question about independent castles.

[Tuidjy]

In one of my games, I am besieging an independent castle. It's a fortified city.
I assume that once I breach the walls, I will face defenders. I fully intend
to waste one turn sending a commander to probe their strength, but I would still
like to hear what I am likely to find. Random independents? A preset army,
probably made out of elite forces? Nothing whatsoever?

This castle is not one left by a defeated player, I am sure of it. I am reasonably
sure it was there before anyone took the province and searched it, although I admit
that I did not see the province when it was independent - another player was
besieging the castle before I came.