Just clarifying, The Reach was an ethnic Breton enclave, and the forsworn are Bretons who aren't happy about not ruling it independently?

All I know is that they make a satisfying thud when struck with a hammer.

The Forsworn were Bretons living in that area before the Nords came and conquered the land, the Forsworn rejected any and all treaties and refused to give up their own gods and ways of culture, if I have it all correct.

If that's correct, it makes for an interesting comparison that the Nords are being the same to the Forsworn as the Imperial Empire is being to the Nord/Skyrim culture regarding Talos.