[JaydedOne]

Another suggestion is to pillage, pillage, and pillage some more and maybe ritual in some Black Death or other mass-death of your elemental choice while you're at it. I'm still a rookie, so I'm not sure if the supplies in a keep are a fixed number which aren't affected by the population, but if they in fact are, then that's a great way to continue smoking him out. Even if fort supply -isn't- dependent on such, you can at least get it to the point where there's very little he can build anew in that province given the loss in resources and potentially start cutting into his upkeep money.