Aizkolaritza is the Basque name for a type of wood-chopping competition. They are a popular form of herri kirol (rural sport) in the Basque Country. Competitions are commonly held at most festivals, especially town festivals and usually involve at least two individuals or teams competing against each other.
Small segments of Vacas were used by Medem in his documentary film "La pelota vasca" to illustrate the Carlist Wars.
Historically, the Basques allied themselves initially with the Carlists (who were right-wing) but later with the Spanish Republic (who were left-wing) because, in each case, they were promised local autonomy.
Julio Médem illustrates the cyclical nature of the unresolved strife and vacillating alliance between the two rival families in the film by using the same actor to portray generations of characters. The actor Carmelo Gómez's plays the cowardly Manuel Iriguíbel in the Carlist Wars, Manuel's son Ignacio in 1905, and eventually, the matured photographer, Peru Mendiluze, who returns the Basque region at the onset of the Spanish Civil War in 1936. Kandido Uranga plays first the doomed Carmelo Mendiluze in 1875 and then Carmelo's obsessive and haunted son Juan in the other three segments of the film. Karra Elejade plays both Ilegorri and Ilegorri's son Lucas.
The film begins in the trenches of Biscay in 1875 during the Third Carlist War, was the last Carlist War in Spain. The Carlist Wars were a series of civil wars that took place in Spain during the 19th century. The contenders fought to establish their claim to the throne, although some political differences also existed. Indeed, several times during the period from 1833 to 1876 the Carlists - followers of Don Carlos, an infante, and his descendants - rallied to the cry of "God, Country, and King" and fought for the cause of Spanish tradition (Legitimism and Catholicism) against liberalism, and later the republicanism, of the Spanish governments of the day. The Carlist Wars had a strong regional component (Basque region, Catalonia, etc.), given that the new order called into question region-specific law arrangements and customs kept for centuries.