Führer Headquarters
At the beginning of World War II there were no permanent headquarters constructed for the German supreme leader, the "Führer". Hitler visited the frontlines by using either aeroplane or his special train, the "Führersonderzug"; thus, the "Führersonderzug" can be considered as the first of his field headquarters. The first permanent installation which became a Führer Headquarters was the "Felsennest", which was used by Hitler during the Battle of France in May, 1940. Hitler actually spent very little time in Berlin during the war, and the dwellings he most frequently used were the "Berghof" and the "Wolfsschanze", spending more than 800 days at the latter.