I remember last time I came there, it was occupied with Forsworn. I killed them all. Later, when I came back, it's occupied by the Imperial Legion, as if the Imperial Legion questline is completed. I didn't actually take sides. When I entered, the soldiers say that I'm interferring or something. Almost same dialoges as when they walk on the roads with a Stormcloak prisoner. When I met the commander, he said "You're tresspassing here, you need to clear out". I have no idea what happened. Why did the Imperial Legion take Fort Sungard without joining sides and doing Civil War quest missions?