The problem is when things like "Netherlands declare independence from a large, 100% religious unity Burgundy" happen.
I mean.. you can go to war and conquer them back, no? There are many frustrating things that can happen and you need to respond to either mitigate the damage or accept loses and try to win them back later.
From a logical perspective, nothing stops a country from declaring independence... they can wake up tomorrow and say "we're free", but that doesn't mean you can't go and forcefully annex them.
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