Corps A corps ( " core " ; the plural is spelled the same as singular but pronounced " cores " ; from French , from the Latin " corpus " " body " ) is either a large military formation composed of two or more divisions , or an administrative grouping of troops within an armed force with a common function , such as Artillery or Signals . Corps may also refer to a particular unit or a particular branch of service , such as the United States Marine Corps , the Corps of Royal Marines , the Honourable Corps of Gentlemen at Arms , or the Corps of Commissionaires . The military term was subsequently adopted for public service organizations with a paramilitary command structure , volunteer public service organizations , such as the Peace Corps , various ambulance corps , some NGOs ( non - government organizations ) , and other civic volunteer organizations . Due to this use of the term , it has also spread to some other civic or volunteer organizations that lack the paramilitary structure . Military formation . In many armies , a corps is a battlefield formation composed of two or more division s , and typically commanded by a lieutenant general . During World War I and World War II , due to the large scale of combat , multiple corps were combined into armies which then formed into army group s . In Western armies with numbered corps , the number is often indicated in Roman numerals ( e . g . , VII Corps ) . Australia . In the later stages of World War I , the five infantry divisions of the First Australian Imperial Force ( AIF ) — consisting entirely of personnel who had volunteered for service overseas — were united as the Australian Corps , on the Western Front , under Lieutenant General Sir John Monash . During World War II , the Australian I Corps was formed to co - ordinate three Second Australian Imperial Force ( 2nd AIF ) units : the 6th , 7th and 9th Divisions , as well as other Allied units on some occasions , in the North African campaign and Greek campaign . Following the commencement of the Pacific War , there was a phased withdrawal of I Corps to Australia , and the transfer of its headquarters to the Brisbane area , to control Allied army units in Queensland and northern New South Wales ( NSW ) . II Corps was also formed , with Militia units , to defend south - eastern Australia , and III Corps controlled land forces in Western Australia . Sub - corps formations controlled Allied land forces in the remainder of Australia . I Corps headquarters was later assigned control of the New Guinea campaign . In early 1945 , when I Corps was assigned the task of re - taking Borneo , II Corps took over in New Guinea . Canada . Canada first fielded a corps - sized formation in the First World War ; the Canadian Corps was unique in that its composition did not change from inception to the war ' s end , in contrast to British corps in France and Flanders . The Canadian Corps consisted of four Canadian divisions . After the Armistice , the peacetime Canadian militia was nominally organized into corps and divisions but no full - time formations larger than a battalion were ever trained or exercised . Early in the Second World War , Canada ' s contribution to the British - French forces fighting the Germans was limited to a single division . After the fall of France in June 1940 , a second division moved to England , coming under command of a Canadian corps headquarters . This corps was renamed I Canadian Corps as a second corps headquarters was established in the UK , with the eventual formation of five Canadian divisions in England . I Canadian Corps eventually fought in Italy , II Canadian Corps in NW Europe , and the two were reunited in early 1945 . After the formations were disbanded after VE Day , Canada has never subsequently organized a Corps headquarters . Republic of China ( 1911 – 1947 ) . An NRA Corps ( 軍團 ) was a type of military organization used by the Chinese Republic , and usually exercised command over two to three NRA Division s and often a number of Independent Brigade s or Regiment s and supporting units . The Chinese Republic had 133 Corps during the Second Sino - Japanese War . After losses in the early part of the war , under the 1938 reforms , the remaining scarce artillery and the other support formations were withdrawn from the Division and was held at Corps , or Army level or higher . The Corps became the basic tactical unit of the National Revolutionary Army having strength nearly equivalent to an allied Division . France . The French Army under Napoleon used corps - sized formations ( ) as the first formal combined - arms groupings of division s with reasonably stable manning and equipment establishments . Napoleon first used the Corps d ' Armée in 1805 . The use of the Corps d ' Armée was a military innovation that provided Napoleon with a significant battlefield advantage in the early phases of the Napoleonic Wars . The Corps was designed to be an independent military group containing cavalry , artillery and infantry , and capable of defending against a numerically superior foe . This allowed Napoleon to mass the bulk of his forces to effect a penetration into a weak section of enemy lines without risking his own communications or flank . This innovation stimulated other European powers to adopt similar military structures . The Corps has remained an echelon of French Army organization to the modern day . Poland ( 1938 – 39 ) . The Polish Armed Forces used Independent Operational Group ' s in the place of the Corps before and during World War Two . An example woulde be Independent Operational Group Polesie . The groups , as the name indicates , were more flexible and showed greater capacity to absorb and integrate elements of broken units over a period of just a couple days and keep cohesion during the September Campaign than more traditional army units such as divisions , regiments , or even brigades . United Kingdom . The British Army still has a corps headquarters for operational control of forces . I Corps of the British Army of the Rhine was redesignated the Headquarters Allied Command Europe Rapid Reaction Corps in 1994 . It is no longer a purely British formation , although the UK is the ' framework nation ' and provides most of the staff for the headquarters . A purely national Corps headquarters could be quickly reconstituted if necessary . It took command of the International Security Assistance Force in Afghanistan on 4 May 2006 . Previously , it was deployed as the headquarters commanding land forces during the Kosovo War in 1999 and also saw service in Bosnia and Herzegovina , commanding the initial stages of the IFOR deployment prior to that in 1996 . Otherwise , the only time a British corps headquarters has been operationally deployed since 1945 was II Corps during the Suez Crisis . United States . The first corps in the United States Army were legalized during the American Civil War by an Act of Congress on July 17 , 1862 , but Major General George B . McClellan designated six corps organizations within his Army of the Potomac that spring . Prior to this time , groupings of divisions were known by other names , such as " wings " and " grand divisions " . The terminology " Army Corps " was often used . These organizations were much smaller than their modern counterparts . They were usually commanded by a major general , were composed of two to six divisions , although predominantly three , and typically included from 10 , 000 to 15 , 000 men . Although designated with numbers that are sometimes the same as modern U . S . Army corps , there is no direct lineage between the 43 U . S . corps of the Civil War and those with similar names in the 20th century due to Congressional legislation caused by the outcry from Grand Army of the Republic veterans during the Spanish – American War . In the Confederate States Army , corps were authorized in November 1862 . They were commanded by lieutenant generals and were usually larger than their Union Army counterparts because their divisions contained more brigades , each of which could contain more regiments . All of the Confederate corps at the Battle of Gettysburg , for instance , exceeded 20 , 000 men . However , for both armies , unit sizes varied dramatically with attrition throughout the war . In Civil War usages , by both sides , it was common to write out the number , thus " Twenty - first Army Corps " , a practice that is usually ignored in modern histories of the war . During World War I the American Expeditionary Forces ( AEF ) adopted the common European usage of designating corps by Roman numerals As of 2003 , the United States Army has four field corps . The structure of a field corps is not permanent ; many of the units that it commands are allocated to it as needed on an " ad hoc " basis . On the battlefield , the field corps is the highest level of the forces that is concerned with actually fighting and winning the war . Higher levels of command are concerned with administration rather than operations , at least under current doctrine . The corps provides operational direction for the forces under its command . Corps are designated by consecutive Roman numerals . The present active corps in the US Army are I Corps ( " eye core " ) , III Corps , V Corps ( deactivated June 2013 ) , and XVIII Airborne Corps ; their numbers derive from four of the 24 corps [ numbers I - XVI , XVIII - XXIV and XXXVI ] that were formed during World War II . It also refers to a grouping of specialized troops such as the Army Corps of Engineers , Army Signal Corp and the United States Marine Corps . Soviet Union . The pre - World War II Red Army of the former USSR had rifle corps much like in the Western sense with approximately three divisions to a corps . However , after the war started , the recently purged Soviet senior command ( Stavka ) structure was apparently unable to handle the formations , and the armies and corps were integrated . Rifle Corps were re - established during the war after Red Army commanders had gained experience handling larger formations . Before and during World War II , however , Soviet armored units were organized into corps . The pre - war Mechanized Corps were made up of divisions . In the reorganizations , these " Corps " were reorganized into tank brigade s and support units , with no division structure . Due to this , they are sometimes , informally , referred to as " Brigade Buckets " . After the war , the Tank and Mechanized Corps were re - rated as divisions . During the reforms of 1956 - 58 , most of the corps were again disbanded to create the new Combined Arms and Tank Armies . A few corps were nevertheless retained , of both patterns . The Vyborg and Archangel Corps of the Leningrad Military District were smaller armies with three low - readiness motorized rifle divisions each . The Category A Unified Corps of the Belarussian Military District ( Western TVD / Strategic Direction ) and Carpathian Military District ( also Western TVD ) were of the brigade pattern . The Soviet Air Forces used ground terminology for its formations down to squadron level . As intermediates between the Aviation Division and the Air Army were Corps — these also had three Air Divisions each . Administrative Corps . In the British Army and the armies of many Commonwealth countries , a corps is also a grouping by common function , or an Arm or a Service ( e . g . Intelligence Corps , Royal Logistic Corps , Royal Corps of Signals ) , performing much the same function as a ceremonial infantry or cavalry regiment , with its own cap badge , stable belt , and other insignia and traditions . The Royal Armoured Corps and the Corps of Infantry are looser groupings of independent regiments . Australia . In Australia , soldiers belong foremost to a Corps which defines a common function or employment across the army . The Australian Army has a system of coloured lanyards , which each identify a soldier as part of a specific Corps ( or sometimes individual battalion ) . This lanyard is a woven piece of cord which is worn on ceremonial uniforms and dates back to the issue of clasp knives in the early 20th century which were secured to the uniform by a length of cord . If a soldier is posted to a unit outside of their parent corps , except in some circumstances the soldier continues to wear the hat badge and lanyard of their Corps ( e . g . a Clerk posted to an infantry battalion would wear the hat badge of the Royal Australian Ordnance Corps but would wear the lanyard of the battalion they are posted to . ) Canada . In Canada , with the integration of the Canadian army into the Canadian Forces , the British Corps model was replaced with personnel branch es , defined in Canadian Forces Administrative Orders ( CFAOs ) as " . . . cohesive professional groups . . . based on similarity of military roles , customs and traditions . " " CFAO 2 - 10 ) " However , the Armour Branch has continued to use the title Royal Canadian Armoured Corps , the Infantry Branch continued to use the Royal Canadian Infantry Corps designation , and the Artillery Branch uses the term Royal Regiment of Canadian Artillery . When the Army , Royal Canadian Navy , and Royal Canadian Air Force were merged in 1968 to form the Canadian Forces , the Royal Canadian Dental Corps and Royal Canadian Army Medical Corps were deactivated and merged with their Naval and Air Force counterparts to form the Dental Branch ( Canadian Forces ) and the Canadian Forces Medical Service of the Canadian Forces Health Services Group ( CF H Svcs Gp ) . The Royal Canadian Army Service Corps transport and supply elements were combined with the Royal Canadian Ordnance Corps to form the Logistics Branch The Royal Canadian Army Service Corps clerical trades were merged with the Royal Canadian Army Pay Corps and the Royal Canadian Postal Corps to form the Administration Branch ( later merged with the Logistics Branch ) Other " corps " , included : Canadian Engineer Corps , Signalling Corps , Corps of Guides , Canadian Women ' s Army Corps , Royal Canadian Army Veterinary Corps , Canadian Forestry Corps , Canadian Provost Corps and Canadian Intelligence Corps . United States . The Corps system is also used in the U . S . Army to group personnel with a common function , but without a regimental system there is less variation in insignia and tradition . These are often referred to as " Branches " and include the Quartermaster Corps , Ordnance Corps , Transportation Corps , Medical Corps , Nurse Corps , Chaplain Corps , Judge Advocate General ' s Corps , & Finance Corps . Each of these Corps is also considered a " Regiment " for historic purposes but these Regiments have no tactical function . Non - military use . The Salvation Army calls its local units / church " corps " ( e . g . The Rockford Temple Corps , The St . Petersburg Citadel Corps ) , echoing the pseudomilitary name and structure of the organization . In the United Kingdom , the Royal Observer Corps was a civil defence unit disbanded in 1995 . In the US , there are non - military , administrative , training and certification Corps for commissioned officers of the government ' s uniformed services , such as the United States Public Health Service Commissioned Corps and the National Oceanic and Atmospheric Administration Commissioned Corps . Many volunteer municipal or university ambulance , rescue , and first aid squads are known as VACs ( volunteer ambulance corps ) . Prominent examples are the Order of Malta ( the largest in Ireland ) , Hatzolah ( largest VAC network worldwide ) , Hackensack VAC . The usage of the term Ambulance Corps dates to Civil War Major General George B . McClellan ' s General Order No 147 to create an " ambulance corps " within the Union Army . GO 147 used " Corps " in one of its standard military senses . However , subsequent formations of non - military ambulance squads continued to use the term , even where they adhere less to paramilitary organizational structure . The Peace Corps was organized by the United States as an " army " of volunteers . Some Non - governmental organizations ( NGOs ) are known as corps . Examples include Global Service Corps and Mercy Corps . A Patent Examiner in the US is a member of the Examiner Corps .