The problem is that it is a strange limitation and the kingdom works with strange logic, so it makes it frustrating. In other words, my lands border on the Aserai. I form an army, I gain more land from the Aserai, but the land does not come to me, but to some lords who live on the northern tip of the map. The thing is, the game is forcing you not to conquer. If you conquer it does not give you any reward, because then you will not be able to get those lands in the future, because they will belong to a lord of your own faction. If they wanted to make the option to become a vassal unplayable, they could notify first. Look, this is unplayable, but you can do it ...
