At 11:50 hours, the ironclad "Numancia" opened fire on the defenses. The Peruvian fort "Santa Rosa" fired back soon after. No shot hit the Spanish warships, so the guns had to be recalibrated; a loss of time that could have been avoided if the Peruvian artillery had begun firing over the Spanish ships while they were taking up positions. When the batteries resumed their fire, a shot hit the "Numancia" injuring the Spanish Admiral Méndez Nuñez. The ship, however, suffered no damage thanks to its armor. The "Cañón del Pueblo", a 500-pound Blakely gun, became unusable as the heavy recoil made it derail.