XII Corps ( United Kingdom ) XII Corps was an army corps of the British Army in World War I and World War II . In World War I , it formed part of the British Salonika Force on the Macedonian front . In World War II , it formed part of Second Army during the Normandy and North - West Europe campaigns of 1944 - 45 . World War I . XII Corps was formed in France on 8 September 1915 under the command of Lt - Gen Sir Henry Fuller Maitland Wilson . In November 1915 , XII Corps was sent from France with 22nd , 26th and 28th Division s under command to reinforce Allied forces on the Macedonian front . Wilson and his corps headquarters ( HQ ) arrived at the port of Salonika on 12 November , but the commander of the British Salonika Force ( BSF ) took XII Corp ’ s staff to establish his own HQ . On 14 December 1915 , the War Office sanctioned the establishment of two corps within the BSF and Wilson reformed XII Corps . After a period holding the defensive position known as ‘ the Birdcage ’ around Salonika , XII Corps moved up - country in July 1916 , taking over former French positions , but only part was involved in the fighting during the summer and autumn . XII Corps was selected to attack the Bulgarian positions west of Lake Doiran in April 1917 . The area to be attacked was ‘ a defender ’ s dream , being a tangled mass of hills cut by numerous ravines ’ . Wilson planned a three - stage operation to capture the three lines of defences , preceded by a short intense bombardment . The BSF ’ s commander , Sir George Milne decided that his manpower was too limited , and reduced this to a smaller assault on the first defence line only , preceded by a three - day bombardment to neutralise enemy batteries and destroy trenches and barbed wire . This , of course , lost the element of surprise and the Bulgarians were well aware of what was coming . Only three brigades were engaged , but the casualties were high and little ground was gained . In a second attack two weeks later , the assault troops managed to cross no man ’ s land , but it was difficult to get information back to HQs , and some companies simply disappeared . This 1st Battle of Doiran ( second battle by Bulgarian reckoning ) had been a failure and , with many troops being withdrawn to other theatres , XII Corps did not get another opportunity to launch a major attack until 18 September 1918 . On that day , with two brigades of 22nd Division and the Greek Seres Division , XII Corps failed to take ‘ Pip Ridge ’ and the ‘ Grande Couronne ’ . The following day , the attack was renewed with a brigade from 27th Division supported by the remnants of 22nd Division , the Seres Division , and the French 2nd Regiment of Zouaves . Once more the attack failed with heavy casualties . However , the 2nd Battle of Doiran had served its purpose by drawing Bulgarian attention away from Gen Franchet d ’ Esperey ’ s main Franco - Serbian thrust , which broke through the Bulgarian lines further west . On 21 September , the BSF was ordered to pursue the retreating Bulgarians , with XII Corps in the lead . Bulgaria signed an armistice with the Allies on 29 September , but XII Corps continued to advance across Bulgaria towards the Turkish frontier , until the Ottoman Turks also signed the Armistice of Mudros on 31 October . XII Corps occupied parts of European Turkey and Wilson was appointed GOC Allied Forces Gallipoli and Bosporus . On 11 February 1919 , XII Corps ceased to exist , Wilson becoming Commander , Allied Forces Turkey in Europe , British Salonika Army , and British Army of the Black Sea . Composition of XII Corps in World War I . Order of Battle ( March 1917 ) Corps Troops : World War II . Home defence . XII Corps , which was formed in 1940 , was part of the United Kingdom ' s Home Forces in the early part of World War II . Lieutenant - General Bernard Montgomery was its commander from 27 April 1941 until 13 August 1942 , when he was sent to Egypt to take command of Eighth Army . Order of Battle , June - October 1940 North West Europe . XII Corps was designated as one of the follow - up corps of the British Second Army . In July 1944 , it took over command of the troops holding the Odon Valley area in July 1944 ( previously under command of the British VIII Corps ) . It took part in a diversionary action in the area prior to Operation Goodwood ( 18 – 20 July 1944 ) , and was then involved in the fighting southwards out of this area in August . The Corps was the last assignment of the 59th ( Staffordshire ) Infantry Division prior to the division ' s disbandment in August . XII Corps supported the left flank of XXX Corps during Operation Market Garden in September 1944 ; but , like VIII Corps on the right flank , struggled to match the pace of XXX Corps ' rapid advance . This left XXX Corps ' flanks exposed to German counter - attacks on its lines of communication , and was one of the major factors in the British failure at Arnhem . Order of battle , June 1944 < br > General Officer Commanding Lt - Gen Neil Ritchie < br > Corps Troops Attached formations Divisions attached at other times General Officers Commanding . Commanders included :