On March 19, 1367, what came to be known as the Battle of Inglesmendi (the English Mount) near Ariñez/Ariñiz in Araba took place. Here, once again in history, the Basque Country was the site of a broader conflict that even drew in European powers. Araba had been part of the Kingdom of Castile since 1199 and this was an episode in the Castilian Civil War, a war of succession in the period 1351-1369 that ultimately became part of a larger conflict then raging between England and France, the Hundred Years’ War (1337-1453). Basically, England supported the succession to the Castilian throne of the reigning monarch, King Peter, the Cruel, while France supported (tacitly rather than officially) the candidacy of his illegitimate brother Count Henry of Trastámara.
Throughout March, Henry’s forces, including significant Aragonese noblemen and French free companies led by the Breton knight Betrand du Guesclin, engaged their counterparts on the side of Peter, a similar mercenary force made up principally of English and Gascons and led by Edward of Woodstock, the so-called Black Prince, the eldest son of Edward III, King of England. Henry’s forces were adept at the use of guerrilla tactics against the superior numbers of the Black Prince.
In the Inglesmendi encounter, a vanguard of Henry’s army formed by jinetes (Castilian light cavalry) had wiped out a detachment of the Black Prince’s army and then headed back to their base. On their way, they met with an exploration detachment of the Black Prince’s army. After suffering many casualties, the Black Prince’s troops entrenched in a nearby mountain, where English longbowmen resisted Henry’s Castilian light cavalry. The cavalry then changed tactics; its French and Aragonese horsemen dismounted and attacked as infantry, winning the battle, and taking many prisoners. Thereafter, the mountain would be known as Inglesmendi (the English Mount, in Basque).
It was a surprise defeat for the Black Prince, hitherto considered invincible. However, while his forces were temporarily demoralized by the setback, he ultimately recovered, and with broader political events favoring King Peter, he ultimately defeated Henry’s troops at the Battle of Nájera in La Rioja on April 3. That said, Henry himself managed to escape across the Pyrenees and continued to fight Peter. Moreover, Peter lost the support of England on account of his non-payment of dues for the assistance offered, was isolated internationally, and was eventually killed by Henry at the Battle of Montiel in 1369, resulting in Henry II assuming the throne of Castile.