Terminology of Military Units – Part 2: High Level Formations

Above the division, there are several more layers of military formation that can be created when the size of the forces in a theatre of operations becomes large enough to warrant them. Unlike the division, these are not usually permanent formations, only being created when several divisions come together in one place (though as always, there are exceptions to this rule).

Corps:  this is a confusing word as it has several different meanings. In some contexts it can mean an arm of service or a particular profession within the military. An example of this include the Royal Armoured Corps – a name that covers all tank units within the British Army even though these will never all serve together. The Royal Armoured Corps will never exist as a group of men together in one place. Rather it is a virtual unit for giving a sense of belonging to a profession and bringing together experience and knowledge about how tanks are used.

Another use of the word corps is as an army within an army, for example the US Marine Corps.

But the meaning I want to discuss here is as a real operation military formation, when it is a grouping of several divisions (2 or 3, typically) to fight together. The important parts of a corps are the headquarters, which co-ordinates the divisions under its command, and the various support arms it might have such as heavy artillery which doesn’t usually exist at divisional level. In addition there will be non-combat support services such as pioneer or engineer units to keep the roads and railways supplying the combat units useable.

Army: if a theatre of operations is large enough to have half a dozen or more corps operating in it, the decision might be made to organise them into several armies. The level of army as a formation was the highest level grouping created in the British Army during the First and Second World Wars. An example is the 8th Army, the formation that encompassed all British forces fighting in the North African desert in the latter stages of the campaigns against Rommel.

Army Group:this level of formation only needs to be created when there are truly astonishing numbers of soldiers fighting in a theatre of operation and where there would be too many armies for one single theatre commander to keep track of. It came into its own on the Eastern Front in the Second World War, where the size of the forces was astounding. The German invasion of Russia in 1941 (Operation Barbarossa) saw 4.5 million German and German-ally soldiers invading Russia along a front of 1,800 miles. To make the planning of such a vast operation manageable, the front was divided into 3 army groups: Army Group North, Army Group Centre and Army Group South.

As far as I am aware, no formation higher than an army group has even been created. No nation has ever brought together enough men in one theatre of operations at one time to make it necessary, and let us hope they never will. The horrors of army groups of over a million men clashing on the Eastern Front in the Second World War were bad enough without imagining slaughter involving tens of millions of soldiers.

Links to other parts of this series:

Part 1: infantry formations, divisional level and below: http://socyberty.com/military/terminology-of-military-units-part-1-infantry-formations-divisional-level-and-below/

Part 3: tank and artillery units: http://socyberty.com/history/terminology-of-military-units-part-3-tank-and-artillery-units/