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 the First World War until the end of the Cold War, longer than any other corps. It had a short-lived precursor during the Waterloo Campaign. It served as the operational component of the British Army of the Rhine during the Cold War, and was tasked with defending West Germany.
VIII Corps was a British Army corps formation that existed during the First and Second World Wars. In the latter, it took part in the Normandy Campaign in 1944, where it was involved in Operation Epsom and Operation Goodwood. It would later play a supporting role in Operation Market Garden and finish the war by advancing from the Rhine to the Baltic Sea.
IV Corps was a corps-sized formation of the British Army, formed in both the First World War and the Second World War. During the First World War the corps served on the Western Front throughout its existence. During the Second World War it served in Norway and Britain until it was transferred to India, which was threatened with attack after Japan entered the war.
The II Corps was an army corps of the British Army formed in both the First World War and the Second World War. There had also been a short-lived II Corps during the Waterloo Campaign.
III Corps was an army corps of the British Army formed in both the First World War and the Second World War.
The Essex Yeomanry was a Reserve unit of the British Army that originated in 1797 as local Yeomanry Cavalry Troops in Essex. Reformed after the experience gained in the Second Boer War, it saw active service as cavalry in World War I and as artillery in World War II. Its lineage is maintained by 36 Signal Squadron, part of 71 (Yeomanry) Signal Regiment, Royal Corps of Signals.
The 1st Cavalry Division was a regular Division of the British Army during the First World War where it fought on the Western Front. During the Second World War it was a first line formation, formed from Yeomanry Regiments. It fought in the Middle East before being converted to the 10th Armoured Division.
V Corps was an army corps of the British Army that saw service in both the First and the Second World Wars. It was first organised in February 1915 and fought through the First World War on the Western front. It was recreated in June 1940, during the Second World War and was substantially reorganised in 1942 for participation in Operation Torch. It fought through the Tunisia Campaign and later the Italian Campaign.
The Queen's Own Oxfordshire Hussars (QOOH) was a Yeomanry Cavalry regiment of the British Army's auxiliary forces, formed in 1798. It saw service in the Second Boer War with 40 and 59 Companies of the Imperial Yeomanry and was the first Yeomanry regiment to serve in Belgium and France during the Great War. After almost four years of Trench warfare on the Western Front, where cavalry had been superfluous, the QOOH led the advance during the Allies' victorious Hundred Days Offensive in 1918. In 1922, the QOOHt became part of the Royal Artillery and during World War II it served as anti-tank gunners at Singapore and in North West Europe. After a series of postwar mergers and changes of role, the regiment's lineage is maintained by 142 Vehicle Squadron, Royal Logistic Corps.
The 7th (Meerut) Division was an infantry division of the Indian Army and before 1895, the Bengal Army, that saw active service during World War I.
The 3rd (Lahore) Division was an infantry division of the Indian Army and before 1895, the Bengal Army, first organised in 1852. It saw service during World War I as part of the Indian Corps in France before being moved to the Middle East where it fought against troops of the Ottoman Empire.
The South Irish Horse was a Special Reserve cavalry regiment of the British Army. Formed as an Imperial Yeomanry regiment in 1902 as the South of Ireland Imperial Yeomanry, it perpetuated a unit formed during the Second Boer War. It transferred to the Special Reserve (Cavalry) in 1908 and was renamed as the South Irish Horse. Having taken part in the fighting of World War I, it was disbanded after Irish Independence in 1922.
The Duke of Lancaster's Own Yeomanry (DLOY) was a yeomanry unit of the British Army from 1798 to 1992. Originally raised as part-time cavalry for home defence and internal security, the regiment sent mounted infantry to serve in the Second Boer War. During World War I it carried out mounted duties in Egypt and Palestine and on the Western Front. By 1917 the reserve units at home had become cyclists and the regiment serving on the Western Front joined an infantry battalion, seeing action at the Battle of Passchendaele, against the German Spring Offensive and in the final Allied Hundred Days Offensive. At the beginning of World War II the regiment gave up its horses and formed two regiments of medium artillery, which served in the Middle East, Italy and North West Europe. Postwar it became an armoured unit. Today its lineage is maintained by B Squadron, the Queen's Own Yeomanry.
The Royal Buckinghamshire Yeomanry is an Operational Hygiene Squadron of the Royal Logistic Corps, originally formed as cavalry in 1794, and has also served in artillery and signals roles. The lineage is continued by 710 Operational Hygiene Squadron, Royal Logistic Corps.
The South African 1st Infantry Brigade was an infantry brigade of the army of the Union of South Africa during World Wars I and II. During World War I, the brigade served as a British formation in Egypt and on the Western Front, most famously the Battle of Delville Wood. It was reactivated at the start of the Second World War as a South African formation and served in East Africa and the Western Desert; the brigade disbanded on 1 January 1943.
The XXI Corps was an Army Corps of the British Army during World War I. The Corps was formed in Palestine in August 1917 under the command of Lieutenant General Edward Bulfin. It formed part of the Egyptian Expeditionary Force (EEF) and served in the Sinai and Palestine Campaign. At the Battle of Sharon it fought what has been described as 'one of the most overwhelmingly successful operations of the war' and 'a precursor to the modern Blitzkrieg.' It then carried out remarkable march up the coast of modern-day Lebanon as the war came to an end.
XI Corps was a corps-sized formation of the British Expeditionary Force, active during the First World War that served on the Western Front and in Italy. It was recreated as part of Home Forces defending the United Kingdom during the Second World War.
VI Corps was an army corps of the British Army in the First World War. It was first organised in June 1915 and fought throughout on the Western Front. It was briefly reformed during the Second World War to command forces based in Northern Ireland, but was reorganized as British Forces in Ireland one month later.
The Structure of the Egyptian Expeditionary Force over the course of the First World War is shown below.
United Kingdom 
British Army