I know there's some trick to it, but how?
I know there's some trick to it, but how?
In vanilla, you can just abandon a crusade, remove the unit and then rejoin, I think. Otherwise, you can take a settlement and move on with your general. Any units left behind as garrison will stop crusading the next turn.
So it has to be taken and then left in the same turn, that explains it.
leaving them as garrison for a city or fort doesn't prevent them to "desert"?
If you conquer the settlement while crusading and then leave crusading units without a general in the settlement, they stop crusading on the next turn and therefore do not suffer from desertion. I must admit I haven't experimented much with this, so I can't tell whether the same would apply if you just build a fort and leave some crusading units behind in it without conquering anything or the like.