XVIII Reserve Corps was formed on the outbreak of the war in August 1914 as part of the mobilisation of the Army. It was initially commanded by GeneralleutnantKuno von Steuben, formerly of the Prussian War Academy. It was still in existence at the end of the war in the 18th Army, Heeresgruppe Deutscher Kronprinz on the Western Front.
Structure on formation
On formation in August 1914, XVIII Reserve Corps consisted of two divisions, made up of reserve units. In general, Reserve Corps and Reserve Divisions were weaker than their active counterparts
Reserve Infantry Regiments did not always have three battalions nor necessarily contain a machine gun company
Reserve Jäger Battalions did not have a machine gun company on formation
Reserve Cavalry Regiments consisted of just three squadrons
Reserve Field Artillery Regiments usually consisted of two abteilungen of three batteries each
Corps Troops generally consisted of a Telephone Detachment and four sections of munition columns and trains 
In summary, XVIII Reserve Corps mobilised with 24 infantry battalions, 5 machine gun companies (30 machine guns), 6 cavalry squadrons, 12 field artillery batteries (72 guns) and 3 pioneer companies. It included one active Infantry Regiment (168th).
^Cron 2002, p. 111 About a third of Reserve Infantry Regiments formed in August 1914 lacked a machine gun company
^Cron 2002, p. 116 Active Jäger Battalions had a machine gun company with the exceptions of the 1st and 2nd Bavarian Jäger Battalions
^Cron 2002, p. 128 Most active cavalry regiments had four squadrons, some were raised to six squadrons
^Cron 2002, p. 134 Active Divisions had a Field Artillery Brigade of two regiments
^Cron 2002, p. 86 Active Corps Troops included a battalion of heavy howitzers (Foot Artillery), an Aviation Detachment, a Telephone Detachment, a Corps Pontoon Train, a searchlight section, 2 munition column sections, one Foot Artillery munitions column section and two Train sections
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