Zubiaur was born to a Carlist family; his father knew personally the claimant Don Jaime and in the early 1910s he was involved in the Miguelist plot in Portugal. José Ángel adopted the Carlist outlook as a natural way of life, especially that also San Martín de Unx was part of the Carlist Navarrese heartland. Already during his early schooling years the boy he was active in Juventudes Jaimistas, a Carlist youth organization; during the Republican period he grew to executive positions within the organization, though information available is confusing. Later Zubiaur admitted having taking part in Traditionalist Pamplonese feasts, though he remained silent on any organizational commitments of the early 1930s. Following the coup of July 1936 he volunteered to the Carlist militia, the requeté, and spent almost 3 years on the front; he served mostly in one of field companies of Radio Requeté, first in Tercio de Navarra and then in Tercio de Lácar. He survived the Biscay, Santander and Asturias campaigns unharmed, until during the Battle of Teruél he suffered frostbites and had to be treated in the Pamplona hospital He finished the wartime career as a sergeant.