In November 1936 he participated in the Villarreal offensive. In February and March 1937 Marcelino Bilbao fought with the Isaac Puente battalion in the siege of Oviedo, integrated into the 1st Brigade of the Basque Expeditionary Brigades. Faced with General Mola's offensive, he participated in the withdrawal of the Guipuzcoan fronts, was a direct witness to the bombardment of Guernica and fought in the battle of Sollube. After the fall of the Bilbao's Iron Ring, it went to Santander and from there to Asturias, participating in the Battle of Mazuco. In this battle, the entire battalion was decorated with the Medal of Freedom (highest distinction of the Second Spanish Republic) awarded by Belarmino Tomás, president of the Sovereign Council of Asturias and León, to the commander of the battalion, Antonio Teresa de Miguel.