Alpine Fortress

The Alpine Fortress (German: Alpenfestung) or Alpine Redoubt was the World War II national redoubt planned by Heinrich Himmler in November/December 1943 for Germany's government and armed forces to retreat to an area from "southern Bavaria across western Austria to northern Italy". The plan was never fully endorsed by Hitler and no serious attempt was made to put the plan into operation.

In the six months following the D-Day landings in Normandy in June 1944, the American and British armies advanced to the Rhine and seemed poised to strike into the heart of Germany, while the Soviet Army, advancing from the east through Poland, reached the Oder. It seemed likely that Berlin would soon fall and Germany be divided. In these circumstances, it occurred both to some leading figures in the German regime and to the Allies that the logical thing for the Germans to do would be to move the government to the mountainous areas of southern Germany and Austria, where a relatively small number of determined troops could hold out for some time.

A number of intelligence reports to the Supreme Headquarters of the Allied Expeditionary Forces (SHAEF) identified the area held stores of foodstuffs and military supplies built up over the preceding six months, and could even be harbouring armaments production facilities. Within this fortified terrain, they said, Hitler would be able to evade the Allies and cause tremendous difficulties for the occupying Allied forces throughout Germany.

The minister of propaganda, Joseph Goebbels, set up a special unit to invent and spread rumours about an Alpenfestung. Goebbels also sent out rumours to neutral governments, thus keeping the Redoubt myth alive and its state of readiness unclear. He enlisted the assistance of the intelligence service of the SS, the SD, to produce faked blueprints and reports on construction supplies, armament production and troop transfers to the Redoubt. This utter deception of allied military intelligence is considered to be one of the greatest feats of the German Abwehr during the entire war.

...
Wikipedia