# I Corps (German Empire)

The I Army Corps / I AK (German: I. Armee-Korps) was a corps level command of the Prussian and then the Imperial German Armies from the 19th Century to World War I.
It was established with headquarters in Königsberg (now Kaliningrad, Russia). Initially, the Corps catchment area comprised the entire Province of East Prussia, but from 1 October 1912 the southern part of the Province was transferred to the newly formed XX Corps District.
In peacetime, the Corps was assigned to the I Army Inspectorate, which became the 8th Army at the start of the First World War. The corps was still in existence at the end of the war, and was disbanded with the demobilisation of the German Army after World War I.

## Austro-Prussian War

The I Corps fought in the Austro-Prussian War against Austria in 1866, including the Battle of Trautenau and the Battle of Königgrätz.

## Franco-Prussian War

The Corps served in the Franco-Prussian War against France in 1870–1871. It saw action in the Battle of Noiseville, the Battle of Gravelotte, the Siege of Metz, the Battle of Amiens, the Battle of Hallue, and the Battle of St. Quentin, among other actions.

## Peacetime organisation

From formation in 1820, the Corps commanded two divisions: 1st Division and 2nd Division. These were joined by 37th Division when it was formed on 1 April 1899. 37th Division was transferred to XX Corps when it was formed on 1 October 1912.
The 25 peacetime Corps of the German Army (Guards, I - XXI, I - III Bavarian) had a reasonably standardised organisation. Each consisted of two divisions with usually two infantry brigades, one field artillery brigade and a cavalry brigade each. Each brigade normally consisted of two regiments of the appropriate type, so each Corps normally commanded 8 infantry, 4 field artillery and 4 cavalry regiments. There were exceptions to this rule:
    V, VI, VII, IX and XIV Corps each had a 5th infantry brigade (so 10 infantry regiments)
    II, XIII, XVIII and XXI Corps had a 9th infantry regiment
    I, VI and XVI Corps had a 3rd cavalry brigade (so 6 cavalry regiments)
    the Guards Corps had 11 infantry regiments (in 5 brigades) and 8 cavalry regiments (in 4 brigades).
Each Corps also directly controlled a number of other units. This could include one or more
    Foot Artillery Regiment
    Jäger Battalion
    Pioneer Battalion
    Train Battalion
Peacetime organization of the Corps :
| Corps | Division | Brigade | Units | Garrison |
| I Corps | 1st Division | 1st Infantry Brigade | 1st (1st East Prussian) Grenadiers "Crown Prince" | Königsberg |
| I Corps | 1st Division | 1st Infantry Brigade | 41st (5th East Prussian) Infantry "von Boyen" | Tilsit, III Bn at Memel |
| I Corps | 1st Division | 2nd Infantry Brigade | 3rd (2nd East Prussian) Grenadiers "King Frederick William I" | Königsberg |
| I Corps | 1st Division | 2nd Infantry Brigade | 43rd (6th East Prussian) Infantry "Duke Charles of Mecklenburg" | Königsberg, II Bn at Pillau |
| I Corps | 1st Division | 1st Field Artillery Brigade | 16th (1st East Prussian) Field Artillery | Königsberg |
| I Corps | 1st Division | 1st Field Artillery Brigade | 52nd (2nd East Prussian) Field Artillery | Königsberg |
| I Corps | 1st Division | 1st Cavalry Brigade | 3rd (East Prussian) Cuirassiers "Count Wrangel" | Königsberg |
| I Corps | 1st Division | 1st Cavalry Brigade | 1st (Lithuanian) Dragoons "Prince Albrecht of Prussia" | Tilsit |
| I Corps | 2nd Division | 3rd Infantry Brigade | 4th (3rd East Prussian) Grenadiers "King Frederick the Great" | Rastenburg |
| I Corps | 2nd Division | 3rd Infantry Brigade | 44th (7th East Prussian) Infantry "Count Dönhoff" | Goldap |
| I Corps | 2nd Division | 4th Infantry Brigade | 33rd (East Prussian) Fusiliers "Count Roon" | Gumbinnen |
| I Corps | 2nd Division | 4th Infantry Brigade | 45th (8th East Prussian) Infantry | Insterburg, Darkehmen |
| I Corps | 2nd Division | 2nd Field Artillery Brigade | 1st (1st Lithuanian) Field Artillery "Prince August of Prussia" | Gumbinnen, Insterburg |
| I Corps | 2nd Division | 2nd Field Artillery Brigade | 37th (2nd Lithuanian) Field Artillery | Insterburg |
| I Corps | 2nd Division | 2nd Cavalry Brigade | 12th (Lithuanian) Uhlans | Insterburg |
| I Corps | 2nd Division | 2nd Cavalry Brigade | 9th Jäger zu Pferde | Insterburg |
| I Corps | 2nd Division | 43rd Cavalry Brigade | 8th (East Prussian) Uhlans "Count zu Dohna" | Gumbinnen, Stallupönen |
| I Corps | 2nd Division | 43rd Cavalry Brigade | 10th Jäger zu Pferde | Angerburg, Goldap |
| I Corps | Corps Troops | | 5th Machine Gun Abteilung | Insterburg |
| I Corps | Corps Troops | | 1st Fortress Machine Gun Abteilung | Königsberg |
| I Corps | Corps Troops | | 1st (East Prussian) Foot Artillery "von Linger" | Königsberg, Lötzen (Feste Boyen) |
| I Corps | Corps Troops | | 1st (East Prussian) Pioneer Battalion "Prince Radziwill" | Königsberg |
| I Corps | Corps Troops | | 18th (Samland) (Fortress-) Pioneer Battalion | Königsberg |
| I Corps | Corps Troops | | 5th Fortress Telephone Company | Königsberg |
| I Corps | Corps Troops | | 5th Airship Battalion | Graudenz, Königsberg, Schneidemühl |
| I Corps | Corps Troops | | 1st (East Prussian) Train Battalion | Königsberg |

## World War I
### Organisation on mobilisation

On mobilization on 2 August 1914, the Corps was restructured. The 1st and 2nd Cavalry Brigades were withdrawn to form part of the 1st Cavalry Division and the 43rd Cavalry Brigade was broken up and its regiments assigned to the divisions as reconnaissance units. The Divisions received engineer companies and other support units from the Corps headquarters. In summary, I Corps mobilised with 24 infantry battalions, 8 machine gun companies (48 machine guns), 8 cavalry squadrons, 24 field artillery batteries (144 guns), 4 heavy artillery batteries (16 guns), 3 pioneer companies and an aviation detachment.
Initial wartime organization of the Corps :
| Corps | Division | Brigade | Units |
| I Corps | 1st Division | 1st Infantry Brigade | 1st Grenadier Regiment |
| I Corps | 1st Division | 1st Infantry Brigade | 41st Infantry Regiment |
| I Corps | 1st Division | 2nd Infantry Brigade | 3rd Grenadier Regiment |
| I Corps | 1st Division | 2nd Infantry Brigade | 43rd Infantry Regiment |
| I Corps | 1st Division | 1st Field Artillery Brigade | 16th Field Artillery Regiment |
| I Corps | 1st Division | 1st Field Artillery Brigade | 52nd Field Artillery Regiment |
| I Corps | 1st Division | | 8th Uhlan Regiment |
| I Corps | 1st Division | | 1st Company, 1st Pioneer Battalion |
| I Corps | 1st Division | | 1st Divisional Pontoon Train |
| I Corps | 1st Division | | 1st Medical Company |
| I Corps | 1st Division | | 3rd Medical Company |
| I Corps | 2nd Division | 3rd Infantry Brigade | 4th Grenadier Regiment |
| I Corps | 2nd Division | 3rd Infantry Brigade | 44th Infantry Regiment |
| I Corps | 2nd Division | 4th Infantry Brigade | 33rd Fusilier Regiment |
| I Corps | 2nd Division | 4th Infantry Brigade | 45th Infantry Regiment |
| I Corps | 2nd Division | 2nd Field Artillery Brigade | 1st Field Artillery Regiment |
| I Corps | 2nd Division | 2nd Field Artillery Brigade | 37th Field Artillery Regiment |
| I Corps | 2nd Division | | 10th Jäger zu Pferde Regiment |
| I Corps | 2nd Division | | 2nd Company, 1st Pioneer Battalion |
| I Corps | 2nd Division | | 3rd Company, 1st Pioneer Battalion |
| I Corps | 2nd Division | | 2nd Divisional Pontoon Train |
| I Corps | 2nd Division | | 2nd Medical Company |
| I Corps | Corps Troops | | I Battalion, 1st Foot Artillery Regiment |
| I Corps | Corps Troops | | 14th Aviation Detachment |
| I Corps | Corps Troops | | 1st Corps Pontoon Train |
| I Corps | Corps Troops | | 1st Telephone Detachment |
| I Corps | Corps Troops | | 1st Pioneer Searchlight Section |
| I Corps | Corps Troops | | Munition Trains and Columns corresponding to II Corps |

### Combat chronicle

On mobilisation, I Corps was assigned to the 8th Army to defend East Prussia, while the rest of the Army executed the Schlieffen Plan offensive in August 1914. It saw action at the battles of Stallupönen, Gumbinnen, and Tannenberg, and the First Battle of the Masurian Lakes.
The Corps was still in existence at the end of the war.

## Commanders

The I Corps had the following commanders during its existence:
| From | Rank | Name |
| 18 March 1814 | General der Infanterie | Friedrich Graf Bülow von Dennewitz |
| 5 March 1816 | General der Kavallerie | Karl Ludwig von Borstell |
| 18 June 1825 | Generalleutnant | Karl August von Krafft |
| 30 March 1832 | Generalleutnant | Oldwig von Natzmer |
| 29 November 1839 | General der Kavallerie | Friedrich Graf von Wrangel |
| 7 April 1842 | General der Kavallerie | Karl Friedrich Emil zu Dohna-Schlobitten |
| 28 March 1854 | General der Infanterie | Franz Karl von Werder |
| 29 January 1863 | General der Infanterie | Adolf von Bonin |
| 30 October 1866 | General der Infanterie | Eduard Vogel von Falckenstein |
| 4 August 1868 | General der Kavallerie | Edwin Freiherr von Manteuffel |
| 15 July 1873 | General der Infanterie | Albert Freiherr von Barnekow |
| 5 June 1883 | Generalleutnant | Walther von Gottberg |
| 1 June 1885 | Generalleutnant | Christian Ewald von Kleist |
| 15 June 1889 | General der Infanterie | Paul Bronsart von Schellendorff |
| 29 June 1891 | General der Infanterie | Hans Wilhelm von Werder |
| 10 January 1895 | General der Infanterie | Karl Graf Finck von Finckenstein |
| 27 January 1902 | General der Infanterie | Colmar Freiherr von der Goltz |
| 11 September 1907 | General der Infanterie | Alexander von Kluck |
| 1 October 1913 | Generalleutnant | Hermann von François |
| 8 October 1914 | Generalleutnant | Robert Kosch |
| 11 June 1915 | General der Infanterie | Johannes von Eben |
| 5 June 1917 | General der Infanterie | Arnold von Winckler |
| 25 February 1918 | Generalleutnant | Wilhelm Groener |
| 28 March 1918 | Generalleutnant | Theodor Mengelbier |
| 14 December 1918 | General der Infanterie | Johannes von Eben |
| 25 February 1919 | Generalleutnant | Ludwig von Estorff |