When I walked the Camino de Santiago (Catholic pilgrimage across Spain) there was one segment near the Pyrenees where lots of aggressive graffiti seemed to warn that "you are in Basque country now!"
Basque nationalism was quite a thing a few decades ago. I recall once my grandparents driving us from Pau in France down to Bilbao to see the Guggenheim, at one point we drove past the bombed out remains of a politicians car that had happened recently enough that it was still smoking.
Well, Basque nationalism is still a thing, as they hold the 58% of the seats in their parliament. What we don't have now, fortunately, are armed Basque nationalist organizations.