I Corps ( United Kingdom ) I Corps was an army corps in existence as an active formation in the British Army for most of the 80 years from its creation in World War I until the end of the Cold War , longer than any other corps . It had a short - lived precursor during the Waterloo Campaign . Napoleonic precursor . Assembling an army in Belgium to fight Napoleon ’ s resurgent forces in the spring of 1815 , the Duke of Wellington formed it into army corps , deliberately mixing units from the Anglo - Hanoverian , Dutch - Belgian and German contingents so that the weaker elements would be stiffened by more experienced or reliable troops . As he put it : ‘ It was necessary to organize these troops in brigades , divisions , and corps d ’ armee with those better disciplined and more accustomed to war ’ . He placed I Corps under the command of the Prince of Orange and it was this corps that was first contacted by the advancing French at Quatre Bras on 16 June 1815 . However , Wellington did not employ the corps as tactical entities , and continued his accustomed practice of issuing orders directly to divisional and lower commanders . When he drew up his army on the ridge at Waterloo , elements of the various corps were mixed up , and although he gave the Prince of Orange nominal command of the centre , that officer had different forces under him . Subsequent to the battle , the corps structure was re - established for the advance into France , I Corps being commanded by Maj - Gen Sir John Byng , the Prince of Orange having been wounded at Waterloo . Composition of I Corps in the Waterloo Campaign . GOC : General HRH The Prince of Orange Prior to World War I . After Waterloo the army corps structure largely disappeared from the British Army , except for ad hoc formations assembled during annual manoeuvres ( e . g . Army Manoeuvres of 1913 ) . In 1876 a Mobilisation Scheme for eight army corps was published , with ' First Corps ' based on Colchester . In 1880 First Corps ' organization was : This scheme had been dropped by 1881 . The Stanhope Memorandum of 1891 ( drawn up by Edward Stanhope when Secretary of State for War ) laid down the policy that after providing for garrisons and India , the army should be able to mobilise three army corps for home defence , two of regular troops and one partly of militia , each of three divisions . Only after those commitments , it was hoped , might two army corps be organised for the unlikely eventuality of deployment abroad . When war with the Boer Republics was imminent in September 1899 , a Field Force , referred to as the Army Corps ( sometimes 1st Army Corps ) was mobilised and sent to Cape Town . It was , in fact , ' about the equivalent of the First Army Corps of the existing mobilization scheme ' , and was placed under the command of Gen Sir Redvers Buller , GOCinC of Aldershot Command . However , once in South Africa the corps never operated as such , and the three divisions ( 1st , 2nd and 3rd ) were widely dispersed . The 1901 Army Estimates introduced by St John Brodrick allowed for six army corps based on the six regional commands ( Aldershot , Southern , Irish , Eastern , Northern and Scottish ) of which only I Corps ( Aldershot Command ) and II Corps ( Southern Command on Salisbury Plain ) would be entirely formed of regular troops . However , these arrangements remained theoretical , the title ' I Corps ' being added to Aldershot Command . In 1907 the title changed to ' Aldershot Corps ' but reverted to simply ' Aldershot Command ' the following year . Finally , the Haldane Reforms of 1907 established a six - division British Expeditionary Force for deployment overseas , but only Aldershot Command possessed two infantry divisions and a full complement of ‘ army troops ’ to form an army corps in the field . World War I . Pre - war planning for the British Expeditionary Force ( BEF ) did not envisage any intermediate headquarters between GHQ and the six infantry divisions , but it was assumed that if corps HQs became necessary , then the GOC Aldershot Command would automatically become GOC I Corps in the field . On mobilisation in August 1914 the decision was made to conform to the two - division army corps organisation employed by the French armies alongside which the BEF was to operate . Sir Douglas Haig , then commanding at Aldershot , therefore took I Corps HQ to France with 1st Division and 2nd Division under command , and it remained on the Western Front throughout the war . It had a peripheral part at the Battle of Mons , then saw hard fighting at the Battle of the Aisne and First Battle of Ypres in 1914 , at the Battle of Aubers Ridge in the Spring of 1915 and alongside the Canadian Corps at the Battle of Hill 70 , as well in many other large battles of World War I . Composition of I Corps in World War I . The composition of army corps changed frequently . Some representative orders of battle for I Corps are given here . Order of Battle at Mons 23 August 1914 GOC : Lieut - Gen Sir Douglas Haig By the time of the battles of Aubers Ridge and Festubert ( May 1915 ) , I Corps still had 1st and 2nd Divisions under command , but had been reinforced by 47th ( 1 / 2nd London ) Division of the Territorial Force , and 1st Canadian Division . Once the era of trench warfare had set in on the Western Front ( 1915 – 17 ) , the BEF left its army corps in position for long periods , so that they became familiar with their sector , while rotating divisions as they required rest , training , or transfer to other sectors . On 25 September 1918 , for the final battles , I Corps was transferred from First Army to Sir William Birdwood ' s Fifth Army . " ' Order of Battle during the final advance in Artois 2 October - 11 November 1918 GOC : Lieut - Gen Sir Arthur Holland < br > BGGS : Brig - Gen G . V . Hordern < br > Deputy Adjutant & Quartermaster - General : Brig - Gen N . G . Anderson < br > Commander , Royal Artillery : Brig - Gen H . C . Sheppard < br > Commander , Heavy Artillery : Brig - Gen F . G . Maunsell < br > Commander , Engineers : Brig - Gen H . W . Gordon World War II . Battle of France . During World War II , I Corps ' first assignment was again to the British Expeditionary Force where it was commanded by General Dill , and then Lieut - Gen Barker from April 1940 . After the Germans broke through Allied lines in May 1940 , the BEF was forced to retreat to Dunkirk for evacuation . The GOCinC , Lord Gort , ordered Barker to form the rearguard with I Corps to cover the evacuation , and surrender to the Germans as a last resort . However , the acting commander of II Corps , Maj - Gen Bernard Montgomery , advised Gort that Barker was in an unfit state to be left in final command , and recommended that Maj - Gen Harold Alexander of 1st Division should be put in charge . Gort did as Montgomery advised , and in the event the bulk of I Corps was successfully evacuated . As Montgomery recalled : ' " Alex " got everyone away in his own calm and confident manner ' . Composition of I Corps in the Battle of France . GOC : Lt - Gen M . G . H . Barker North - West Europe . I Corps then remained in the United Kingdom until the landings in Normandy for Operation " Overlord " , where , along with XXX Corps , it was a spearhead corps of Second Army of 21st Army Group . After fighting for two months around Caen , the Corps was subordinated on 1 August 1944 to First Canadian Army for the remainder of the Normandy campaign and the subsequent operations in the Low Countries and Germany until 1 April 1945 . I Corps Headquarters then took over administration of 21st Army Group ' s logistics area around the port of Antwerp , Belgium until the end of the war . During the North - West Europe campaign it was under the command of Lieutenant General John Crocker . Composition of I Corps in NW Europe Campaign . GOC : Lt - Gen John Crocker Attached : Assignments of corps to armies , and divisions to corps , changed frequently during the campaign : As of 6 June 1944 As of 7 July 1944 As of 1 August 1944 ( now part of First Canadian Army ) British Army of the Rhine . After the defeat of Germany , 21st Army Group became the British Army of the Rhine ( BAOR ) , and I Corps was transformed into a corps district , with an administrative , rather than combat , role . It was disbanded in 1947 . However , in October 1951 the corps was reactivated to become the principal combat element of the BAOR , with its HQ based in Bielefeld . In March 1952 , following the reactivation of 6th Armoured Division , its component formations were : Included as part of this was Canada ' s contribution to the NATO land forces in Germany . A Canadian mechanised brigade remained part of BAOR until 1970 . The size of this force , 6 , 700 , was such that it was referred to within British circles as a " light division " . In a following 1958 - 60 reorganisation the Corps was formed into three mixed armour / infantry divisions including five brigade groups , which were in 1965 brought together into three centralised divisions . With the end of National Service manpower across the whole of BAOR dropped from around 77 , 000 to 55 , 000 . In the late 1970s the Corps was reorganised as four small five battle group armoured divisions plus a roughly brigade sized infantry ' Field Force ' . It then comprised : Following the 1981 - 3 reorganisation , the Corps consisted of 1st and 4th Armoured Divisions , which would have manned the front line against the anticipated attack by the Soviet 3rd Shock Army , plus in an in - depth , reserve role the 3rd Armoured Division and finally the 2nd Infantry Division which was tasked with rear - area security . With the end of the Cold War , I ( BR ) Corps was redesignated in 1992 as a NATO Rapid Reaction Corps under SACEUR and renamed as Headquarters Allied Command Europe Rapid Reaction Corps . HQ ARRC moved to Rheindahlen in 1994 . General Officers Commanding . Commanders have included : " Note : I Corps was disbanded at the end of World War I and reformed at the start of World War II " " Note : I Corps was disbanded in June 1947 and reformed in late 1951 "