The German Army was organized into Heeresgruppen (Army Groups), which were usually composed by more than two Armeen (Armies). The Befehlshaber im Rückwärtigen Heeresgebiet (Supreme Commander of the Rear Area, abbreviated RHG, e.g. RHG B for Heeresgruppe B) was responsible for security and antipartisan warfare in the Rückwärtige Heeresgebiet (the area immediately behind the front). Some of these Army Groups included units from several Axis countries. For example, Heeresgruppe Africa contained both German and Italian Armies.

Heerestruppen

As it was a command structure, the Heeresgruppe had relatively few units directly subjected, most of all transmission units. The Befehlshaber im Rückwärtigen Heeresgebiet was usually assigned Sicherungs-Divisionen (Security Divisions), Security and Guard units, and partly police units.

An Armeeoberkommando (AOK) was the command level between Army Group and Corps. It was usually commanded by a Generaloberst (Colonel General) or above, and controlled several Armee-Korps (usually form three to six).
The area of responsibility of an AOK was split between the Operational Area, which was further subdivided at corps and divisional level, and the Army Rear Area, which was run by the Kommandanten rückwärtiges Gebiet (Korück or Rear Area Commander).
Demands and allocation of logistic supplies usually went straight to the Oberquartiermeister (Senior Quartermaster) of the AOK; the Army Group command was only involved in situations of crisis.
In the course of the war, as a stopgap alongside the AOKs in certain places, were formed ad hoc formations called Armeeabteilungen (Army Detachments) and Kampfgruppen (Battle Groups) at Army level. As they were ad hoc units, such formations would be named from their Commanders, and often did not have the usual levels of command support.

Armeetruppen
The AOK had its own Armeetruppen (Army Troops) like Heavy Artillery, Engineers and other specialist troops that were subordinated to it depending on availability and task. It also had substantial Versorgungstruppen (Supply Units) and Sanitätseinrichtungen (Medical facilities) because among his tasks was to manage the whole supply system.
To maintain order and security in the Rear Area to the AOKs were detached Sicherungs- and Ordnungstruppen (usually at least one Feldgendarmerie-Abteilung, alas some Feld- and Ortskommandanturen with the relatives Sicherungsbataillonen), one Korück (Kommandantur des rückwärtigen Armeegebiets) and sometimes a Sicherungs-Division.
It usually received at least one Armee-Nachrichten-Regiment and often some Luftwaffe units (Flying units and Flak), but only auf Zusammenarbeit angewiesen (assigned for collaboration) and not directly subjected. Depending on the dimensions of the rückwärtigen Armeegebiets (Rear Area), could be assigned a Zivilverwaltung (Civil Administration) and some Wehrwirtschaftseinheiten (litteraly War Economy Units).

An Armeekorps (AK) was the command level between Army and Division. It was usually commanded by a General der... (Lieutenat General) or above, and controlled several Divisionen (from two to five, usually three).

Korpstruppen

At the beginning of the war the German Army Corps had some Korpstruppen permanently subjected: Nachrichten-Abteilung (Transmission Battalion), Artillerie-Regiment (Artillery Regiment), 2-3 Pionier-Bataillone (Engineer Battalions), Versorgungstruppen (Supply Troops), Feldgendarmerie (Military Police). After 1940 the Korpsstäbe (Corps HQs) only had: one Nachrichten-Abteilung, feeble Versorgungstruppen and the Feldgendarmerie. All other units were temporarily attached only when needed.

A Division is a large military unit or formation, usually consisting of between 10,000 and 25,000 soldiers. To accomplish the different tasks in the battlefield there are many different types. As a rule, the components of the German Divisions during World War Two were Brigades and/or Regiments for the main arms (Infantry, Tanks and Artillery) and Battalions of the support Arms (Anti Tank, Engineer, Supply and so on).