I recently heard something in a Cliffside Bunker video that shocked me – if you have an ally without a capital (like France after G1), you can’t take control of their territories just by walking in; you have to wait until an opponent takes control of it, then take it from them.
I checked the rules, and the example of taking control of a capital-less ally’s territory are in the Conclude Combat section. Since there’s no combat involved in moving into an ally’s territory, I guess that’s technically correct.
But it seems like a ridiculous oversight.