We have two options to assault Arcachon, go through Soniel with its level 2 walls. Since it takes at least 2-3 turns to cross the water that gives Arcachon plenty of time to get their army plus the 6k militia behind those walls. The other option is to go through the land that used to belong to OW and attack through a rural. You could detour even more and go through populated regions, but really we are already stretching the time the army can be away from the realm and still be effective.
Since OW seem to think they have the skills and efficiency to TO parts of Arcachon, maybe they finally have it together enough to reclaim rogue regions on their borders first. I doubt it though, with very few exceptions the only nobility in OW that I had any respect for joined the new realm.
