I have been trying to figure out what the best way is to organise expeditions and as far as I am aware the only way is take all the land leading up to the target province or having cooperation/alliance treaties with all the countries leading up to the region.
My question is, is there a way to move units through territory without actually occupying it (if the territory has a fortress this isn't an issue). This would also be very practical if you want to defeat a nations armies without taking their territory as a way to limit the accumulation of decadence.
Edit: I love that 1.03 came with the solution to the problem an hour after I made the post
(the new abandon territory mechanic)