The Führer Headquarters, Führerhauptquartiere abbreviated FHQu in German, were headquarters used by Nazi leader Adolf Hitler and his close circle of commanders and officials. As Hitler directly controlled much of the German war effort, the FHQu were de facto military headquarters.
This is partial text from the full article (usually with photos) at https://armorama.com/news/read-review-hitler-s-headquarters-in-the-west-then-and-now-by-jean-paul-pallud