Established by the Eastern Command, September 1914, as part of K2. Early days were somewhat chatotic, the new volunteers having very few trained officers and NCOs to command them, no organised billets or equipment. However, by the Spring of 1915, the Division was considered to be ready for France.

25 May 1915 : landed in Boulogne; the Division served with distinction on the Western Front for the remainder of the war, taking part in most of the significant actions.

The Battle of Albert (first phase of the Battle of the Somme 1916)

The Battle of Bazentin (second phase of the Battle of the Somme 1916)

In the latter action, the Division captured Trones Wood.

The Battle of Delville Wood (third phase of the Battle of the Somme 1916) (53rd Brigade)

The Battle of the Ancre Heights (ninth phase of the Battle of the Somme 1916)

In the above action, the Division captured Schwaben redoubt, and helped capture Regina Trench.

The Battle of the Ancre (tenth phase of the Battle of the Somme 1916)

Operations on the Ancre

The German Retreat to the Hindenburg Line

The Third Battle of the Scarpe (fourth phase of the Arras Offensive)

The Battle of Pilckem (first phase of Third Battle of Ypres)

In the above action, the Division helped capture Westhoek.

The Battle of Langemarck (second phase of Third Battle of Ypres) (53rd Brigade)

The First Battle of Passchendaele (seventh phase of the Third Battle of Ypres)

The Second Battle of Passchendaele (eighth phase of the Third Battle of Ypres)

The Battle of St Quentin (first phase of the First Battles of the Somme 1918)

The Battle of the Avre (fifth phase of the First Battles of the Somme 1918)

The Actions of Villers-Bretonneux (sixth phase of the First Battles of the Somme 1918)

The Battle of Amiens

The Battle of Albert (first phase of the Second Battles of the Somme 1918)

The Battle of Bapaume (second phase of the Second Battles of the Somme 1918)

The Battle of Epehy (second phase of the Battles of the Hindenburg Line)

The Battle of the St Quentin Canal (fourth phase of the Battles of the Hindenburg Line)

The Battle of the Selle

The Battle of the Sambre

In total, the Division suffered more than 46,500 casualties during the Great War, of whom 13,727 died. Demobilisation was completed by 20th March 1919.

The Division won 11 awards of the Victoria Cross.

53rd Brigade

8th (Service) Bn, the Norfolks (joined September 1914, disbanded February 1918)

8th (Service) Bn, the Suffolks (joined September 1914, disbanded February 1918)

10th (Service) Bn, the Essex (joined September 1914)

6th (Service) Bn, the Royal Berkshire (joined October 1914, disbanded February 1918)

8th (Service) Bn, the Royal Berkshire (joined February 1918)

7th (Service) Bn, the Royal West Kents (joined February 1918)

53rd Brigade Machine Gun Company (joined 13 February 1916, moved into 18 MG Bn 16 February 1918)

53rd Trench Mortar Battery (joined 17 June 1916)

54th Brigade

10th (Service) Bn, the Royal Fusiliers (joined September 1914, left October 1914)

11th (Service) Bn, the Royal Fusiliers (joined September 1914)

2nd Bn, the Bedfords (joined May 1918)

7th (Service) Bn, the Bedfords (joined February 1915, left May 1918)

8th (Service) Bn, the Royal Sussex (joined September1914, left February 1915)

6th (Service) Bn, the Northamptonshire (joined November 1914)

12th (Service) Bn, the Middlesex (joined September 1914, disbanded February 1918)

54th Brigade Machine Gun Company (joined 13 February 1916, moved into 18 MG Bn 16 February 1918)

54th Trench Mortar Battery (joined 1 June 1916)

55th Brigade

7th (Service) Bn , the Queen's (joined September 1914)

7th (Service) Bn , the Buffs (joined September 1914)

8th (Service) Bn, the East Surreys (joined September 1914)

7th (Service) Bn, the Royal West Kents (joined September 1914, left February 1918)

55th Brigade Machine Gun Company (joined 13 February 1916 , moved into 18 MG Bn 16 February 1918)

55th Trench Mortar Battery (joined 17 June 1916)

Divisional Troops

10th (Service) Bn, the Royal Fusiliers (joined October 1914, left March 1915)

8th (Service) Bn, the Royal Sussex (joined as Pioneers February 1915)

6th (Service) Bn, the Northamptonshire (joined September 1914, left November 1914)

No 18 Machine Gun Battalion (created 16 February 1918)

No 15 Motor Machine Gun Battery (joined 22 July 1915, left 4 May 1916 when transferred to XV Corps)

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Divisional Mounted Troops

C Squadron , the Westmoreland and Cumberland Yeomanry (joined 15 June 1915, left 10 May 1916)

18th Divisional Cyclist Company (formed 8 December 1914, left 21 May 1916)

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Divisional Artillery

LXXXII Brigade, RFA

LXXXIII Brigade, RFA

LXXXIV Brigade, RFA (left as an Army Brigade on 25 January 1917)

LXXXV (H) Brigade, RFA (broken up 3 December 1916)

18th Heavy Battery, RGA (a Battery of 4 60-lbr guns raised with the Division but moved independenetly to Egypt in October 1915. Served most of the war in Salonika.)

18th Divisional Ammunition Column

V.18 and W.18 Heavy Trench Mortar Batteries RFA (V Bty formed 28 April 1916; was attached to Fourth Army TM School until 6 May 1916; left for II Corps on 19 February 1918. W Bty formed 21 May 1916, but broken up by 26 November 1916, having by then received no weapons)

X.18, Y.18 and Z.18 Medium Mortar Batteries RFA (joined by 19 June 1916; by 19 February 1918, Z broken up and batteries reorganised to have 6 x 6-inch weapons each)

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Engineer Units

79th Field Company (joined Sep 1914)

80th Field Company (joined Sep 1914)

92nd Field Company (joined Jan 15)

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Field Ambulances

54th Field Ambulance (joined Jun 1914)

55th Field Ambulance (joined Jun 1914)

56th Field Ambulance (joined Jun 1914)

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18th Divisional Train ASC (150, 151, 152 and 153 Coys ASC)

219th Divisional Employment Company (joined 3 June 1917)

30th Mobile Veterinary Section

35th Sanitary Section ( left 24 March 1917, for Fifth Army)

18th Divisional Motor Ambulance Workshop (on 16 April 1916, absorbed by Divisional Train)