Who developed this defensive plan in the 1880s that has Fort de Cindey as one of its three principal fortified regions?
National Redoubt (Switzerland): The Swiss National Redoubt (German: "Schweizer Reduit" ; French: "Réduit suisse" ; Italian: "Ridotto nazionale" ; Romansh: "Reduit nazional" ) was a defensive plan developed by the Swiss government beginning in the 1880s to respond to foreign invasion.
i don't know