Despite being a convinced socialist with anti-Fascist convictions, Bottecchia joined the Bersaglieri corps of the Italian army during the first world war. For four years he ferried messages and supplies on the Austrian front with a special folding bicycle. During the conflict he contracted malaria and also had to evade capture several times. Bottecchia endured a gas attack on 3 November 1917 after the battle of Caporetto while providing covering fire for retreating forces. Near Sequals he was captured, but escaped while being marched into captivity at night. After returning to Italian lines, he twice conducted reconnaissance sorties into Austrian-held areas, which by now included his home region of Colle Umberto. Bottecchia was later awarded a bronze medal for valor.