The 19th (Western) Division was constituted as follows during the war: ;
56th Brigade : • 7th (Service) Battalion,
King's Own (Royal Lancaster Regiment) (
disbanded February 1918) • 7th (Service) Battalion,
East Lancashire Regiment (
disbanded February 1918) • 7th (Service) Battalion,
South Lancashire Regiment (
disbanded February 1918) • 7th (Service) Battalion,
Loyal North Lancashire Regiment (
disbanded February 1918) •
4th (Extra Reserve) Battalion, King's (Liverpool Regiment) (
joined 3 December 1915, left 15 December 1915) • 56th Machine Gun Company,
Machine Gun Corps (
joined 14 February 1916, moved to 19th Machine Gun Battalion 14 February 1918) • 56th Trench Mortar Battery (
joined 17 June 1916, broken up 5 February 1918, reformed 6 March 1918) • 9th (Service) Battalion,
Cheshire Regiment (
joined February 1918) • 1/4th Battalion,
King's (Shropshire Light Infantry) (
joined February 1918) • 8th (Service) Battalion,
Prince of Wales's (North Staffordshire Regiment) (
joined February 1918) ;
57th Brigade : • 10th (Service) Battalion,
Royal Warwickshire Regiment • 8th (Service) Battalion,
Gloucestershire Regiment • 10th (Service) Battalion,
Worcestershire Regiment (
until June 1918) • 8th (Service) Battalion, Prince of Wales's (North Staffordshire Regiment) (
until February 1918) • 57th Machine Gun Company, Machine Gun Corps (
joined 14 February 1916, moved to 19th Machine Gun Battalion 14 February 1918) • 57th Trench Mortar Battery (
joined 15 June 1916) • 3rd Battalion, Worcestershire Regiment (
joined June 1918) ;
58th Brigade • 9th (Service) Battalion, Cheshire Regiment (
left February 1918) • 9th (Service) Battalion,
Royal Welsh Fusiliers • 5th (Service) Battalion,
South Wales Borderers (
left December 1914) • 9th (Service) Battalion,
Welsh Regiment • 6th (Service) Battalion, Duke of Edinburgh's (Wiltshire Regiment) (
from December 1915 until June 1918) • 58th Machine Gun Company, Machine Gun Corps (
joined 14 February 1916, moved to 19th Machine Gun Battalion 14 February 1918) • 58th Trench Mortar Battery (
joined 15 June 1916) • 2nd Battalion, Duke of Edinburgh's (Wiltshire Regiment) (
joined May 1918) ;
Divisional Troops : • 6th (Service) Battalion, Duke of Edinburgh's (Wiltshire Regiment) (
left December 1914) • 5th (Service) Battalion, South Wales Borderers (
joined as provisional Pioneer battalion December 1914, conversion completed February 1915) • 13th Motor Machine Gun Battery (
joined 14 July 1915, left 7 March 1916) • 246th Machine Gun Company,
Machine Gun Corps (
joined 19 July 1917, moved into 19 Machine Gun Battalion 14 February 1918) • 19th Battalion, Machine Gun Corps (
formed 14 February 1918) ;
Divisional Mounted Troops : • C Squadron,
Queen's Own Yorkshire Dragoons (
joined 26 June 1915, left 21 April 1916) • 19th Divisional Cyclist Company,
Army Cyclist Corps (
formed 19 November 1914, left 21 April 1916) ;
Divisional Artillery : • LXXXVI Brigade,
Royal Field Artillery (
left 23 January 1917) • LXXXVII Brigade, Royal Field Artillery • LXXXVIII Brigade, Royal Field Artillery • LXXXIX (Howitzer) Brigade, Royal Field Artillery (
broken up 8–9 September 1916) • 19th Divisional Ammunition Column Royal Field Artillery • 19th Heavy Battery,
Royal Garrison Artillery (
raised with the division but moved independently to France on 15 July 1915 and joined XXI Brigade, Royal Garrison Artillery) • W.19 Heavy Trench Mortar Battery, Royal Field Artillery (
joined May 1916, disbanded 19 February 1918) • X.19, Y.19 and Z.19 Medium Mortar Batteries, Royal Field Artillery (
formed by May 1916; on 18 February 1918, Z broken up and batteries reorganised to have 6 x 6-inch weapons each) ;
Royal Engineers : • 81st Field Company,
Royal Engineers • 82nd Field Company, Royal Engineers • 94th Field Company, Royal Engineers • 19th Divisional Signals Company, Royal Engineers ;
Royal Army Medical Corps : • 57th Field Ambulance,
Royal Army Medical Corps • 58th Field Ambulance, Royal Army Medical Corps • 59th Field Ambulance, Royal Army Medical Corps • 36th Sanitary Section, Royal Army Medical Corps (
left 9 July 1917) ;
Other Divisional Troops : • 19th Divisional Train
Army Service Corps (
154, 155, 156 and 157 Companies) • 31st Mobile Veterinary Section
Army Veterinary Corps • 220th Divisional Employment Company (
joined 19 July 1917) • 19th Divisional Motor Ambulance Workshop (
absorbed into divisional train 6 April 1916) ==Commanders==