Battle of Andoain

The Battle of Andoain (Basque: Andoaingo Gudua) was a military engagement of the First Carlist War that was fought on 14 September 1837. It took place around the Basque village of Andoain, south of the main Liberal stronghold of San Sebastián. Liberal troops under Leopoldo O'Donnell had captured Andoain on 9 September, driving the Carlist garrison there to the western bank of the Oria. Over the next three days, both sides constructed breastworks amidst intermittent skirmishes. After two days of trench warfare, Carlist troops poured heavy artillery fire on the Liberal lines and launched an all-out offensive, supported by reinforcements brought in from Navarre by José Ignacio de Uranga.

The Liberals were flanked on their left wing, and their lines crumbled. Only two British Auxiliary Legion regiments and a number of their Basque guides, the Chapelgorris, were left to resist the Carlist advance, but were eventually overrun and captured. Most of the Legion's soldiers who surrendered to the Carlists were summarily executed due to popular anger over the Legion's burning of local buildings in the previous weeks. The battle led to the end of the British Auxiliary Legion as an effective fighting force, with two-thirds of their members killed, wounded or executed by the Carlists or local civilians. O'Donnell and the remnants of his forces withdrew to Hernani, Gipuzkoa.