Ersatz is German for "replacement". Ersatz divisions were formed on mobilisation from replacement units of active regiments. Each brigade replacement battalion (Brigade-Ersatz-Bataillone) was numbered after its parent infantry brigade, and was formed with two companies taken from each of the brigade's replacement battalions (of which there was one per infantry regiment). Cavalry ErsatzAbteilungen and Field Artillery ErsatzAbteilungen were likewise formed from active cavalry and field artillery regiments.
Armee-Abteilung Falkenhausen[4] was set up in the southern part of the Western Front in Alsace-Lorraine on 17 September 1914 from the parts of 6th Army that remained in Lorraine after the main body marched north to participate in the Race to the Sea. The Staff of the Ersatz Corps and its commander took command of the Armee-Abteilung and the Ersatz Corps ceased to exist.[5]
^Cron 2002, p. 84 Armee-Abteilung or Army Detachment in the sense of "something detached from an Army". It is not under the command of an Army so is in itself a small Army.
Cron, Hermann (2002). Imperial German Army 1914-18: Organisation, Structure, Orders-of-Battle [first published: 1937]. Helion & Co. ISBN1-874622-70-1.
Ellis, John; Cox, Michael (1993). The World War I Databook. Aurum Press Ltd. ISBN1-85410-766-6.
Busche, Hartwig (1998). Formationsgeschichte der Deutschen Infanterie im Ersten Weltkrieg (1914 bis 1918) (in German). Institut für Preußische Historiographie.
Histories of Two Hundred and Fifty-One Divisions of the German Army which Participated in the War (1914-1918), compiled from records of Intelligence section of the General Staff, American Expeditionary Forces, at General Headquarters, Chaumont, France 1919. The London Stamp Exchange Ltd (1989). 1920. ISBN0-948130-87-3.
The German Forces in the Field; 7th Revision, 11th November 1918; Compiled by the General Staff, War Office. Imperial War Museum, London and The Battery Press, Inc (1995). 1918. ISBN1-870423-95-X.