Answer: Spain
Some extra relevant information:
The Carlist Wars were a series of conflicts that took place in Spain during the 19th century. The wars were primarily fought between two factions: the Carlists, who supported the claim of Carlos María Isidro de Borbón to the Spanish throne, and the liberals, who supported the ruling government and the Isabella II as the rightful heir. These wars occurred between 1833 and 1876, with intermittent periods of peace and resurgences of violence. The Carlist Wars were characterized by their regional nature, with the conflict mainly concentrated in the Basque Country, Catalonia, Navarre, and Aragon. The wars were rooted in political and ideological divisions, as well as regional aspirations for autonomy, and significantly impacted Spain’s political landscape during the 19th century.