On formation in August 1914, IX 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 
The IX Reserve Corps was exceptional as it formed the major part of the North Army so was provided with more Corps Troops than other Reserve Corps: a Foot Artillery Battalion, a Pioneer Regiment and a Field Airship Detachment.
In summary, IX Reserve Corps mobilised with 25 infantry battalions, 5 machine gun companies (30 machine guns), 6 cavalry squadrons, 12 field artillery batteries (72 guns), 4 heavy batteries (16 guns), a Field Airship Detachment and 7 pioneer companies. 17th Reserve Division was slightly stronger than the norm as it included an active infantry brigade.
On mobilisation, IX Reserve Corps was assigned to the North Army, which was held back in Schleswig to defend the German North Sea Coast in case of British landings. It was soon transferred to the Western Front, joining 1st Army in late August.
IX Reserve Corps had the following commanders during its existence:
^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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