At the beginning of the Spanish Civil War, on 17 July, he participated in the capture of the Civil Guard barracks in La Felguera. Two days later he marched at the head of 400 anarcho-syndicalists towards Gijón, where he had a prominent role in the Siege of Gijón, participating in the taking of Simancas barracks and El Coto. After the capture of the headquarters of the "Simancas" regiment, a massacre took place, which Carrocera tried to prevent without success. Later he directed the military operations during the Siege of Oviedo and in September 1936, he was wounded in the Villafría sector, during the fight against the nationalists. Confirmed as a militia major, he became one of the main commanders of the confederal militias in Asturias. The anarcho-syndicalist author Diego Abad de Santillán described him as an "authentic hero".