The effort to protect civilians during the Spanish Civil War launched Organized Passive Defense boards and committees devoted to saving the lives of those swept up by events beyond their choosing. These efforts in-cluded building some of the 20th century’s first bomb shelters to protect civilians from aerial attacks. We re-port here the case of Quart de Poblet, a village in the Republican rearguard, where the construction of bomb shelters and the establishment of a Local Passive Defense Board combined to save the lives of those facing indiscriminate attacks from fascist and anti-government aviation. Preserving the Plaça de la Creu bomb shelter allows future generations to experience war construc-tion firsthand and to understand on a physical-level the decisions organized civilians made to protect their families from the realities of 20th century mechanized war – a new type of war in which civilians unwillingly became the main protagonists.