My idea is to add the inverse of logistics to a province. Build stuff that will impede an enemy's movement through your province. Think of it like mines, traps, blown bridges, etc. It can even be something where the effect is halved (or eliminated) after the province is captured. I personally envision it as full effect (say 25% movement reduction) until province captured, then the movement reduction degrades over the same time period as it took to build the modification.
Any thoughts?
Any thoughts?