From the article, "That DNA is inherited directly from World War II, when bunkers were already an established part of Swiss military strategy. In the early ‘40

From the article, "That DNA is inherited directly from World War II, when bunkers were already an established part of Swiss military strategy. In the early ‘40s, when neutral Switzerland was entirely surrounded by Axis powers, the army famously stocked the Swiss Réduit (“National Redoubt”), a series of military fortifications in the central Alps dating to the 1880s, with supplies and ammunition to prepare for a potential Nazi invasion." From my post, "Founded in the idea to make it too expensive for Nazi Germany to invade."