Corps

Corps (pronounced kore)

(1) A military body with a specific function (intelligence corps, medical corps etc).

(2) A military unit of ground combat forces consisting of two or more divisions and other troops.

(3) A group of persons associated or acting together (diplomatic corps; press corps et al).

(4) In printing, a continental designation that, preceded by a number, indicates size of type in Didot points of 0.0148 inches (3.8 mm).

(5) An alternative word for a corpse (obsolete).

(6) In classical ballet, as the corps de ballet, the group of dancers who are not soloists

1225-1275; Middle English corps and Middle French cors, both derived from Latin corpus (body) from the primitive Indo-European kwerp- (body, form, appearance).  Sense in English evolved from dead body (thirteenth century) to live body (fourteenth century) to body of citizens (fifteenth century).  The modern military sense (dating from 1704) is from French corps d'armée, picked up in English during Marlborough's campaigns, the use at the time not based on a specific number of troops but the more generalized "a part of an army expressly organized and having a head".  In English, pronunciation was corse at first and this persisted until the eighteenth century by which time it was archaic except for poetic use.

The field corps, a tactical unit of an army and which contained two or more divisions, was one of Napoleon’s structural innovations in military re-organization although such formations, ad-hoc or planned, had long been a known feature of battlefield tactics. The word was soon extended to other organized groups under a leader, as in corps de ballet (1826) or corps diplomatique (1796), although with the latter, the leader (dean of the diplomatic corps) is an appointment for ceremonial purposes, often, by convention, extended to the papal nuncio.  The special use Corpsman (enlisted medical auxiliary) was used first by the US military in 1941.

The corps in army organizational structures.

Standard of the Corps of Royal Engineers.  Specialized formations (intelligence corps, medical corps et al) exist in all branches of the military with no rules or consistency in the numbers of their establishment.  However, whereas the structures of navies (squadrons, flotillas, fleets etc) and air forces (flights, squadrons, wings, groups etc) are based on the number of vessels or airframes attached, the army (mostly) defines its organization by the number of personnel allocated, the numbers listed below generally indicative based on historic formations.  

Command Group   Size of Command

Army Group           400,000-2,000000

Army                     150,000-360,000

Corps                    45,000-90,000

Division                 10,000-30,000

Brigade                 1500-5000

Regiment              1500-3500

Battalion               500-1500

Company              175-250

Platoon                 12-60

Squad                   4-24

Most armies use all or a subset of the above although the numbers vary (greatly).  A division is made up of 3-4 brigades, a corps of 3-4 divisions and so on.  In western armies, the numbers listed above reflect the big-scale mass formations used during World War II; peacetime armies are a fraction of the size but the organizational framework is retained, most forces actively using only the smaller clusters.  During WWII, US army command groups tended to be up to twice the size of British units though within the same army, divisions often varied in size, an infantry division being usually larger than the armored.  A corps can be assembled from the armies of more than one nation, the Australian & New Zealand Army Corps (ANZAC) being formed in 1915 prior to deployment as part of the Dardanelles Campaign.  Other organizational tags such as squadron also exist but tend now either to be rare or, like battery, applied to specialized units based on function rather than size.  A special case is troop which is generally an alternative word for platoon but there are exceptions.

In twenty-first century wars, entire divisions are rarely committed operationally and brigade level engagements are regarded as large-scale.  In the world wars of the twentieth century, uniquely big, multi-theatre affairs, the standard battlefield unit tended to be the division of which the Soviet Union fielded nearly five-hundred.  The numbers in the world wars were certainly impressive but in a sense could be deceptive, the percentage of those listed on the establishment actually committed to combat sometimes surprisingly low (though this tended to apply less to those of the USSR).  One British prime-minister, pondering this, complained to the Chief of the Imperial General Staff (and the CIGS was a noted ornithologist) that the army reminded him “…of a peacock; all tail and very little bird”.  Dryly, the field marshal responded by pointing out “the peacock would be a very poorly balanced bird without its tail”.

Royal Flying Corps publicity photograph, 1917.

The Royal Flying Corps (RFC) was created in 1912 as the air arm of the British Army.  Late in the First World War, it was merged with Royal Naval Air Service (RNAS), the Royal Air Force (RAF) being formed on 1 April 1918.  Military aviation didn't however become exclusive to the RAF, the army retaining its own operations, mainly for communications, reconnaissance and meteorological services.  The Admiralty was never entirely happy about the merger and the Fleet Air Arm (FAA), though still an operational unit of the RAF, was formed in 1924, necessitated by the launching that year of the of the Royal Navy's first aircraft carrier.  By 1937, even the RAF was convinced naval aviation was different and in 1939 FAA reverted to the Admiralty, operating both from carriers and ground stations.

United States Army Air Corps Curtiss P-40, 1940.

Military aviation in the US was formalized in 1907 with the creation of the United States Army Air Corps (USAAC); the service renamed to United States Army Air Force (USAAF) in 1941.  It wasn't until 1947 when, as part of the National Security Act of that year that the US Air Force (USAF) was established as the fourth branch of the US military.  Remarkably, given it was the US which in the 1940s created the parameters for modern, carrier-based warfare, the admirals, still hankering for the great set-piece, high seas clash of the battleship fleets (which would never happen, largely because of aircraft), tried in 1919 to abolish naval aviation because there was “…no use the fleet will ever have for aviation."  The naval aviators (pilots work for the air force they say) however weren't forced to walk the plank and the navy received its first carrier in 1922 though the intra and inter service squabbles would continue for years.