The game has numerous forts all over the game. Many of them you take control of during your faction campaign; but, with varying results depending on which side you choose. We'll get into that in a minute. From what I understand, a player can clear all of the bandits out of those strategic forts at anytime. What do I mean by strategic, they are marked on every strategic map in the game with faction flags, depicting which side has claim to it.
I assumed that you could clear these forts out at anytime in the game and a short time later the controlling faction in that hold would automatically take control. I had witnessed this with a few forts; but, there are some that I have cleared out more than once while exploring and bandits re-spawn in it again later. One of the forts I am referring to is Fort Greenwall. The only time I have ever seen this fort maintained by a faction was after taking the hold for the Empire. As a matter of fact, the only time I have seen all of the forts occupied by a faction was with the Empire. If you win the war as a Stormcloak, many of the forts remain occupied by bandits and remain as such even after you clear them.
What I am asking here is; is this intentional or is this a fault with the game?