In Victoria 3 if you play as landlocked state without ports / sea connection you are limited. You can’t attack against countries with which you haven’t land connection. You need to cooperate/play against to your neighborhoods but if something “succeeds” so you can take a state that has no border with you. Or you may accidentally lose your connection to your country. And this could be problem.
On image bellow you could see situation which could be. Good question could be how this went down. So first I declare war to Saxe-Meiningen and after that I found out they can’t be attacked because there isn’t connection by land. So I dragged Bavaria into the war by making a mistake in the diplomatic game…
… so I crossed into Bavaria with my whole army, and so I took a country not adjacent to me. Unfortunately, I gained nothing from Bavaria because they got into the war just by accident.
Problematic is that Saxe-Meiningen isn’t connected to my to my current market by land and they can’t have ports. So they have market access 0% and they have existential problem with high prices of everting. This situation you could typically solve that you build ports in country but when we’re talking about interior states then you must conquer bordering states and thus gain a connections.
Solution: Conquer states between your states
Also if you conquer state like I done then you have truce between states. Which should be problems. Back to mine situation above I had 5 years problems to connect mine new subject because I had truce with Bavaria.
That was annoying, but I used the time to build a bigger and stronger army. And at the same time, I improved my diplomatic relations with the surrounding area, so when true was done then I take Bavaria with practically no losses on my side.