Wikipedia
The Führerreserve (“Officers Reserve”) was set up in 1939 as a pool of temporarily unoccupied high military officers waiting for new assignments in the German Armed Forces during World War II. The various military branches and army groups each had their own pools that they could use as they saw fit. The officers were required to remain at their assigned stations and be available to their superiors, but could not exercise any command function, which was equivalent to a temporary retirement while retaining their previous income. Especially in the second half of the war, more and more politically problematic, troublesome, or militarily incompetent officers were assigned to the Führerreserve.
Examples:
Major Karl August Meinel, 1 August 1942, was shifted into the Führerreserve, because on 13 January 1942 he wrote a critical report to General Hermann Reinecke on the segregation and execution of Russian prisoners of war in prison camp Stalag VII-A by the Gestapo and the Sicherheitsdienst SD (security service) of the Reichsführer SS ( Heinrich Himmler). Stalag VII-A was north of Moosburg, a Bavarian town close to Munich.
Georg Thomas, head of the Military Economics and Armament Office of the Armed Forces Supreme Command, played an essential role in drawing up the starvation policy for the occupied Eastern territories. He was transferred to the Officers Reserve on 20 November 1942 and arrested after the 20 July 1944 assassination attempt on Hitler because of his contacts with the resistance.
Franz Halder, head of the army general staff, planned army operations from 1939 to 1941. He was dismissed in 1942 and transferred to the Officers Reserve. After the assassination attempt on Hitler of 20 July 1944, his involvement in a conspiracy in 1938 came to light, which led to his arrest and imprisonment in Flossenbürg concentration camp. He was freed by U.S. troops in May 1945.
Walther von Brauchitsch became Supreme Commander of the Army in 1938 and was decisively involved in planning Operation Barbarossa. He was dismissed on 19 December 1941 because of the military defeat at Moscow and transferred to the Officers Reserve.