# XXXIX Reserve Corps (German Empire)

The XXXIX Reserve Corps (German: XXXIX. Reserve-Korps / XXXIX RK) was a corps level command of the German Army in World War I.

## Formation

XXXIX Reserve Corps was formed in December 1914. It was part of the second wave of new Corps formed in the early stages of World War I consisting of XXXVIII - XXXXI Reserve Corps of 75th - 82nd Reserve Divisions (plus 8th Bavarian Reserve Division). The personnel was predominantly made up of kriegsfreiwillige (wartime volunteers) who did not wait to be called up. It was still in existence at the end of the war.

### Structure on formation

On formation in December 1914, XXXIX Reserve Corps consisted of two divisions. but was weaker than an Active Corps
* the divisions were organised as triangular rather than square divisions with three infantry regiments rather than four, but had a brigade of two field artillery regiments
* Reserve Infantry Regiments consisted of three battalions but lacked a machine gun company
* Reserve Cavalry Detachments were much smaller than the Reserve Cavalry Regiments formed on mobilisation
* Reserve Field Artillery Regiments consisted of two abteilungen (1 gun and 1 howitzer) of three batteries each, but each battery had just 4 guns (rather than 6 of the Active and the Reserve Regiments formed on mobilisation)
In summary, XXXIX Reserve Corps mobilised with 18 infantry battalions, 2 cavalry detachments, 24 field artillery batteries (96 guns), 2 cyclist companies and 2 pioneer companies.
| Corps | Division | Brigade | Units |
| XXXIX Reserve Corps | 77th Reserve Division | 77th Reserve Infantry Brigade | 255th Reserve Infantry Regiment |
| XXXIX Reserve Corps | 77th Reserve Division | 77th Reserve Infantry Brigade | 256th Reserve Infantry Regiment |
| XXXIX Reserve Corps | 77th Reserve Division | 77th Reserve Infantry Brigade | 257th Reserve Infantry Regiment |
| XXXIX Reserve Corps | 77th Reserve Division | 77th Reserve Field Artillery Brigade | 59th Reserve Field Artillery Regiment |
| XXXIX Reserve Corps | 77th Reserve Division | 77th Reserve Field Artillery Brigade | 60th Reserve Field Artillery Regiment |
| XXXIX Reserve Corps | 77th Reserve Division | | 77th Reserve Cavalry Detachment |
| XXXIX Reserve Corps | 77th Reserve Division | | 77th Reserve Cyclist Company |
| XXXIX Reserve Corps | 77th Reserve Division | | 77th Reserve Pioneer Company |
| XXXIX Reserve Corps | 78th Reserve Division | 78th Reserve Infantry Brigade | 258th Reserve Infantry Regiment |
| XXXIX Reserve Corps | 78th Reserve Division | 78th Reserve Infantry Brigade | 259th Reserve Infantry Regiment |
| XXXIX Reserve Corps | 78th Reserve Division | 78th Reserve Infantry Brigade | 260th Reserve Infantry Regiment |
| XXXIX Reserve Corps | 78th Reserve Division | 78th Reserve Field Artillery Brigade | 61st Reserve Field Artillery Regiment |
| XXXIX Reserve Corps | 78th Reserve Division | 78th Reserve Field Artillery Brigade | 62nd Reserve Field Artillery Regiment |
| XXXIX Reserve Corps | 78th Reserve Division | | 78th Reserve Cavalry Detachment |
| XXXIX Reserve Corps | 78th Reserve Division | | 78th Reserve Cyclist Company |
| XXXIX Reserve Corps | 78th Reserve Division | | 78th Reserve Pioneer Company |

## Combat chronicle

In 1915, the German offensive in Courland was intended to be a diversion while the main effort was made further south by the German 11th Army and Austro-Hungarian 4th Army in the Gorlice–Tarnów Offensive.
Armee-Abteilung Lauenstein (Army Detachment Lauenstein) was formed by upgrading XXXIX Reserve Corps of 10th Army on 22 April 1915. It was named for its commander, Generalleutnant Otto von Lauenstein, who retained simultaneous command of XXXIX Reserve Corps. It was directly under the command of OB East.
Due to its success, it was continuously reinforced until it was raised to the status of an army as the Army of the Niemen on 26 May 1915. Generalleutnant von Lauenstein remained as commander of XXXIX Reserve Corps.

## Commanders

XXXIX Reserve Corps had the following commanders during its existence:
| From | Rank | Name |
| 24 December 1914 | Generalleutnant | Otto von Lauenstein |
| 7 July 1916 | Generalleutnant | Hermann von Staabs |
| 3 December 1917 | General der Infanterie | Hermann von Staabs |
| 16 March 1918 | Generalleutnant | Paul Grünert [de] |
| 23 May 1918 | General der Infanterie | Hermann von Staabs |

## Glossary

* 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.
* Armee-Gruppe or Army Group in the sense of a group within an Army and under its command, generally formed as a temporary measure for a specific task.
* Heeresgruppe or Army Group in the sense of a number of armies under a single commander.