From 1939-1941 Albert Speer adapted it for use as Adolf Hitler's main military command headquarters, under the title Adlerhorst. A compound of air-raid standard concrete bunkers were disguised as seven cottages, under which was an extensive bunker complex which linked them to the castle. But on completion the complex was dismissed by Hitler on a visit in February 1940, and Speer subsequently adapted it to serve as the Luftwaffe headquarters during Operation Sea Lion, the invasion of Great Britain.