Siegfried, SEEG freed, Line was the name of two fortified lines of defense established by Germany in the 1900's. Generals Paul von Hindenburg and Erich Ludendorff had the first Siegfried Line built in the winter of 1916-1917, during World War I (1914-1918). Called the Hindenburg Line by the Allies, the line stretched across northern France and Belgium. British and Australian troops smashed through it in September 1918. See World War I.