Mendoza, an officer in the Spanish Navy, sadly contemplates the cruiser "Cervera," scrapped after so many glorious years of service. He nostalgically recalls the ship's history, so closely linked to his own. There he met Mary, his fiancée, and when they both believed themselves to be the happiest people in the world, the outbreak of the Civil War abruptly separated them. Mary went to seek refuge with her family in the besieged Simancas barracks, which "the Cervera" was ordered to bombard when the enemy stormed it. Mendoza heard nothing more of his fiancée while the war continued. Antonio, the older brother, was assigned to the famous "bous" (cruisers) that carried out such important missions across the open sea, and the younger brother, Manuel, served as an officer on the cruiser "Baleares." Through each of their stories, we learn about the main actions of the battle for control of the sea.