I noticed when reading archers timeline that the end of the 20 years war and the independence of the province coincide.
We never here much about the 20 years war except when it started and that it ended 20 years later.
Now perhaps this war was the Province fighting for freedom since this time was way before the Dark made it to the West.
Since the cath Bruig was busy defending itself it would have been spending all the Taxes etc on warriors to defend themselves and ignoring the Province thus the Province wanted freedom.
This all seems kinda of obvious and I feel it was discussed a long time ago and agreed on.