I’ve heard it said that Harold Bluetooth (for whom the technology is named) “unified” all if Scandinavia.
However, I’ve not been able to find out just HOW he managed that. My cynical side says “unified” is really just a euphemism for conquered. And yes, I know that most large-scale unifications will encounter some resistance. However, there’s a big difference (in my mind) between wiping out a pocket of resistance and slaughtering your way across most of a country or countries.