What effect does occupying an enemy camp (those permanent camps) do?

[adishee]

I noticed the blue background when occupying a small settlement. Is it correct that only the last unit in the stack gets the border? And I didn't see that it reduced upkeep costs, they remained the same.

[Arjos]

The unit with the highest upkeep gets the free slot generally and it does not change the text of the card, but your budget for the turn should not be counting it...

[I_damian]

It seems that only in those minor settlements (the ones that have no buildings) does the most expensive unit get the free slot. In cities capable of supporting a free unit it is not the highest upkeep unit that gets the slot but rather units which are native to that city... units which can be recruited in that city and which the engine considers a free garrison unit. In my Seleukia game I have many units in Antioch. I have a royal guard unit, some cavalry, some Karian warbands and some Euzenoi. It's the Euzenoi that get the two free slots because those are the units which I can recruit from that city.

This was how it worked in Medieval 2. If a city had 2 free unit slots then only units which could be recruited in that city would be able to use the free upkeep slots. So for example if you could recruit town militia there but not spear militia, but you had both town and spear militia in the city, then the free slot would go to the town militia because they can be recruited there whereas spear militia cannot, thus they're not considered a free garrison unit.