Structure of the British Army in the First World War

This page looks at the structure of the British Army during the First World War and is one of a series of articles to help you research soldiers who served in the war:

I also offer a First World War Soldier Research Service.

Structure of the British Army in the First World War

When researching a soldier who served in the First World War you will quickly come across words, abbreviations and acronyms which relate to the structure of the British Army. Without understanding this jargon, you may struggle to interpret the documents you find. In addition, you’ll miss out on further sources of information, in the form of additional war diaries, divisional histories etc.

A British Infantry Battalion in the First World War

Regiments in the British Army were made up of individual battalions which were usually grouped into four as part of an infantry brigade. The number was reduced to three in early 1918 due to a manpower shortage. Three brigades formed the bulk of an infantry division and two or more divisions formed a corps. Two or more corps formed an army group. I’ve written a separate article which goes into greater detail on the structure of an infantry battalion. You will need to find out which formation the battalion served in which can often be found by searching the battalion’s title online.

  • Establishment: 1,007, including 30 officers.
  • Commanded by a Lieutenant Colonel
  • Resources to consult: Battalion, regimental and divisional histories. The war diary of the battalion if it exists, as well as the war diaries of units in the brigade, the brigade headquarters war diary and divisional general staff war diary.

An infantry battalion was divided into a headquarters, machine gun section and four companies (usually lettered A to D, 1 to 4, or W to Z) of 227 officers and men. Companies were split into four platoons of approximately 50 men, with a platoon being subdivided into four sections of 12 men. Five officers of The King’s Own (Royal Lancaster Regiment) are shown below. In total, there were thirty in a battalion. It was not unusual for a battalion to lose 50% of their officers in a single day’s fighting. On the opening day of the Battle of the Somme, 1 July 1916, at least nineteen battalions suffered twenty or more officer casualties. The regiment of these officers can be identified from their cap and collar badges consisting of a lion with Kings Own beneath.

Five British Officers of the First World War

A British Infantry Brigade in the First World War

  • Establishment: 3,000-4,000 men
  • Commanded by a Brigadier General
  • Resources: Divisional history along with regimental and battalion histories if they exist. The main resource will be the war diary of the brigade headquarters, along with the battalions which served with it. The war diaries of the other brigades of the division may also be of use as will the war diary of the division’s general staff.

In 1914, an infantry brigade contained a brigade headquarters and four battalions. Three infantry brigades formed the bulk of an infantry division. In early 1918, due to the inability of the army to replace heavy losses, the number of battalions was reduced to three. The war establishment of an Infantry brigade in 1914 is given below:

  • Headquarters: 4 Officers and 23 Other Ranks.
  • 4 Battalions: 120 Officers and 3,908 Other Ranks.
  • Horses: Riding: 65. Draught: 112. Heavy Draught: 34. Pack: 36.

A British Infantry Division in the First World War

  • Establishment: 16,000-18,000
  • Commanded by a Major General
  • Resources: A divisional history is usually the best starting point followed by the war diaries of the division’s general staff. These war diaries are usually very large containing hundreds of pages each. Then there are brigade headquarters diaries to consult and if you’re researching a particular incident/battle in-depth, then battalion war diaries.

An infantry division was designed so it could operate independently and didn’t just contain infantry battalions. The structure of a division varied throughout the war. The war establishment of an infantry division in 1914 was:

  • 1 Headquarters: 15 Officers and 67 Other Ranks.
  • 3 Infantry Brigades: 372 Officers and 11,793 Other Ranks.
  • 1 Headquarters Divisional Artillery: 4 Officers and 18 Other Ranks.
  • 3 Field Artillery Brigades: 69 Officers and 2,316 Other Ranks.
  • 1 Field Artillery (Howitzer) Brigade: 22 Officers and 733 Other Ranks.
  • 1 Heavy Battery and Ammunition Column: 6 Officers and 192 Other Ranks.
  • 1 Divisional Ammunition Column: 15 Officers and 553 Other Ranks.
  • 1 Headquarters Divisional Engineers: 3 Officers and 10 Other Ranks.
  • 2 Field Companies: 12 Officers and 422 Other Ranks.
  • 1 Signal Company: 5 Officers and 157 Other Ranks.
  • 1 Cavalry Squadron: 6 Officers and 153 Other Ranks.
  • 1 Divisional Train: 26 Officers and 402 Other Ranks.
  • 3 Field Ambulances: 30 Officers and 672 Other Ranks.
  • Total: 585 Officers and 17,488 Other Ranks.
  • Horses: Riding: 1,471. Draught: 3,350. Heavy Draught: 644. Pack:127.

A British Cavalry Regiment in the First World War

British cavalry regiments differed from their infantry counterparts in that they didn’t contain multiple units before the outbreak of war. For example, the 13th Hussars consisted of just one unit whereas the Grenadier Guards, contained three battalions which were joined by another two during the war. The regular cavalry regiments which pre-war contained those serving full-time with the army, formed reserve cavalry regiments in Britain and Ireland during the war. The yeomanry regiments, formed of part-time volunteers pre-war raised second and third-line units which didn’t operate abroad. I’ve written another article focusing on the establishment of a British cavalry regiment in more detail.

  • Establishment: 549, including 26 officers
  • Commanded by a Lieutenant Colonel
  • Resources: British cavalry regiments often have good regimental histories. The unit’s war diary and cavalry brigade headquarters’ war diaries will be the most important sources of information. Then there will be the war diaries of the regiments it served with in the brigade.

In 1914, a cavalry regiment was divided into a Headquarters, Machine Gun Section, and three squadrons. The squadrons were usually designated A, B and C with each containing 227 men, commanded by a Major.

A British Cavalry Brigade in the First World War

  • Establishment: 1,600-2,000+
  • Commanded by a Brigadier General
  • Resources: There is a history of the 6th Cavalry Brigade. The main resources will be the brigade headquarters war diary, its units’ war diaries and the divisional general staff war diary.

In 1914, a cavalry brigade contained a brigade headquarters, three cavalry regiments and a battery of the Royal Horse Artillery. Its establishment varied depending on whether it was acting as part of a Division, or independently. If operating independently a cavalry brigade would contain units from the Royal Engineers and Royal Army Medical Corps. Below is the establishment of a Cavalry Brigade not allotted to a Cavalry Division.

  • Headquarters: 7 Officers and 47 Other Ranks.
  • 3 Cavalry Regiments: 78 Officers and 1,569 Other Ranks.
  • 1 Horse Artillery Battery: 7 Officers and 215 Other Ranks.
  • 1 Ammunition Column: 2 Officers and 115 Other Ranks.
  • 1 Field Troop: 3 Officers and 74 Other Ranks.
  • 1 Signal Troop: 1 Officer and 42 Other Ranks.
  • 1 Cavalry Field Ambulance: 6 Officers and 118 Other Ranks.
  • Total in the field: 104 Officers and 2,180 Other Ranks.
  • Horses Riding: 1,826. Draught: 581. Pack: 32.

A British Cavalry Division in the First World War

  • Establishment: 9,000+
  • Commanded by a Major General
  • Resources: The main resource will be the war diaries of its general staff and brigade headquarters.

A cavalry division contained four cavalry brigades and supporting arms, which would allow it to operate independently. The wartime establishment of a cavalry division in 1914 is given below:

  • Headquarters: 15 Officers and 81 Other Ranks.
  • 4 Cavalry Brigades: 340 Officers and 6,532 Other Ranks.
  • Headquarters Cavalry Divisional Artillery: 3 Officers and 17 Other Ranks.
  • 2 Horse Artillery Brigades: 38 Officers and 1,324 Other Ranks.
  • 1 Field Squadron: 7 Officers and 184 Other Ranks.
  • 1 Signal Squadron: 8 Officers and 198 Other Ranks.
  • 1 Headquarters Divisional Train Army Service Corps: 4 Officers and 22 Other Ranks
  • 4 Cavalry Field Ambulances: 24 Officers and 472 Other Ranks
  • Total: 439 Officers and 8,830 Other Ranks.
  • Horses: Riding: 7,350. Draught: 2,378. Pack: 87.

A British Corps in the First World War

  • Establishment: circa 50,000
  • Commanded by a Lieutenant General

A Corps contained two or more Divisions and was one step below an army group. A corps should not be confused with those units of the arms of service which had corps in their title, Royal Army Medical Corps, Army Service Corps etc.

 A British Army Group in the First World War

  • Establishment: circa 100,000
  • Commanded by a General

An army group contained two or more corps.

Unit Commanded by
Army General
Corps Lieutenant General
Division Major General
Brigade Brigadier General
Battalion Lieutenant Colonel
Company Major
Platoon Lieutenant or Second Lieutenant
Section Corporal

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