The Siege of Bilbao and the Auxiliary Battalion.

The Auxiliary Volunteers battalion was a citizen militia created to defend Bilbao against Carlist attacks, following the liberal model created by the National Militia.
The Auxiliary Battalion was created in April 1872, at the beginning of the first Carlist uprising, under the authority of the City Council. And it was dissolved on April 11, 1876 at the end of the war. Since its creation it was under the direct dependence of the Bilbao city council, whose mayor became head of the aforementioned battalion.
On September 15, 1872, Luis Sacristán was appointed as sole Commander of the Volunteer Corps.
The Battalion was made up of eight companies and the staff consisted of the Commander, two assistants, a doctor, two sergeants, a master gunsmith, a corporal, and an orderly. In total, their number varied from 776 volunteers in January 1874 to 1,125 in April 1874. The number of casualties was 300, 14.5% due to death or illness, 60.6% due to changing positions in the defense of the city and 24'9 due to abandonment or desertion.
The Battalion reflected the composition of Bilbao's society. It was made up mainly of Biscayns, 66%, the rest were natives of other Spanish provinces or the American colonies and 0.5% of foreigners. 71% were under 40 years of age, so we can deduce that the young population of the Villa collaborated in their defense. Most of the assistants were manufacturers, artisans or merchants, which corresponds to the majority professions in the city at that time.
The activity of the Auxiliaries gained great relevance during the Siege of 1874. Of the 5,494 people who defended the city on April 1, 1874, 1,074 were Auxiliaries, almost 20%. As of January 24, 1874, the Auxiliaries covered almost all the garrisons in the square from 7:00 p.m. to 7:00 a.m. Their importance did not lie solely in their military contribution, but they played a very important role in maintaining the morale of the besieged.