The organisation of the British Army during the First World War

D/DLI 7/805/73 Officers of ‘D’ Company, 14^th Battalion, Durham Light Infantry, 1916

A few people have asked me about how, for example 8^th Battalion, fits into the larger scheme of things.  My first thought was ‘that’s straightforward’ but it can get complicated quickly.  To some extent, it depends how much you want to know.  Firstly, I’ll be talking about the Infantry, things will vary for other types of unit.

In the First World War the British Army was organised into a number of separate Armies, dedicated to fighting or home service operations.

Working from the top down, each Army was subdivided into a hierarchy of units.  An infantry regiment and its constituent battalions fit midway between the top level (Army) and the smallest (Section).

Army

Corps

Division

Brigade

Regiment

Battalion

Company

Platoon

Section

It is important to note that whilst the others are all fighting units, the regiment was only an organisational unit.  A regiment, such as the Durham Light Infantry, never fought altogether as one entity. 

As we hold the Regimental archive for the Durham Light Infantry it is the one I know most about and will be using for examples.  Not all of its battalions were formed immediately as the war began (and some were in existence beforehand), but at its largest, there were over 30 battalions at home and overseas.

Above the regimental level is where it becomes complicated as not every battalion was in the same brigade/division/corps.  What’s more, battalions changed brigade, brigades changed division, and divisions changed corps due to the requirements of battle.  Below battalion level, companies could be attached to battalions of other regiments but this was a temporary arrangement.  

D/DLI 2/20/5(30) ‘A’ Company, 20^th Battalion, Durham Light Infantry, taken United Kingdom, [1916]

The Armies are the top level (though they still came under the authority of the government department of the War Office).  The First to Fifth Armies were formed between 1914 and 1916, the British Salonika Army formed in 1915.  The First to Third Home Forces Armies formed in 1914 and disbanded at the end of 1915/early 1916, replaced by the Northern and Southern Home Forces Armies in early 1916.  A battalion could be an Army Troop – not part of the intermediate unit levels – in November 1916 2/9^th DLI became part of the British Salonika Army.

In this context, corps refers to the unit comprising two or more divisions and commanded by a Lieutenant General.  There were also supporting troops that came under direct control of the corps.  The Army Service Corps, for example, used the term differently and were not part of this hierarchy.

Commanded by a Major General, divisions were the basic fighting units of the army and moved around as such; the 5^th Division was in France and Flanders, then moved to Italy.  Some battalions, such as 1/7^th DLI in November 1915 and 1/9^th in February 1918 became Pioneer battalions which were Divisional Troops.  Pioneer battalions worked on building and maintaining the infrastructure and came under the supervision of the division, and were thus not part of a brigade. 

Brigades were commanded by Brigadier Generals and were typically formed of four battalions (reducing to three in 1918).  

D/DLI 7/426/155 13 Platoon, ‘D’ Company, 2^nd Battalion, Durham Light Infantry, taken behind the line at Loos, France, 1917

At full strength, a battalion had about 1000 officers and men led by a Lieutenant Colonel; there were four companies in a battalion, four platoons in a company, and four sections in a platoon.

Explanation of 1/9^th, 2/9^th, 3/9^th:  The Territorial Forces were volunteer battalions of part time soldiers that existed before the war.  In the Durham Light Infantry, there were five territorial battalions, the 5^th to 9^th.  The Territorials were mobilised at the outbreak of the war (see the posts on the Second Battle of Ypres for more about this).  As the majority of these men volunteered to go abroad, a second line reserve unit was raised for each of the territorial battalions for home service.  As these became active on home service, third line units were formed as another reserve.  Many second line units ended up going abroad eventually.  The third line units were either disbanded or in the case of the DLI, merged into other units, in 1916.

D/DLI 2/1/268(21) Sergeants of 1^st Battalion, Durham Light Infantry, taken at Nowshera, India, 1916

It is worth mentioning that not all battalions existing in the army between 1914 and 1918 were considered as fighting in the First World War.  The army had units in India for example and this is where 1^st Battalion DLI spent the war period.  The men serving here were entitled to the British War Medal as this was given for overseas service.  To confuse matters, some were also entitled to the 1914-15 Star and the Victory Medal.  These medals applied to service in a theatre of war and some areas of India were classed as such.  This included the 1^st Battalion DLI who took part in fighting on the North West Frontier with the 1^st (Peshawar) Division.

It is possible to go further into the different types of battalion at which point it gets ever more complex.  As a reference I have used The Long, Long Trail website which I can highly recommend to find out more about what I have been writing about and more information about the brigades, division etc. that battalions were in.  A good starting point is their Order of Battle page.