Great Britain

British soldier resting in a front-line trench on the Somme, Sept 1916.

This picture was taken by Lt Ernest Brooks a British photographer and was captured at the end of September 1916 after the Battle of Thiepval Ridge.  The Allies objective in the battle was to take the high ground held by the Germans between the villages of Thiepval and Courcelette. 

Interesting to note is the material secured over his rifle's action to protect the moving parts and keep them clean in the filth of the trench.

-Bootie

(Colorized pic) Two British soldiers helping two wounded German prisoners at the Battle of Albert on the Somme near Boisselle, France, July 1916.

(Colorized pic) Royal Marines lined up on the deck of HMS Royal Oak around 1916, running through rifle practice while at sea, turning the battleship itself into a floating training ground as they prepared for the demands of wartime service.

(Colorized) Troops departing Letchworth Station, Aug 1914.

Battle of the Somme, 1916 — Allied troops going ‘over the top,’ advancing from their own trench during one of the most costly offensives of the Great War.

Interesting pic (and colorized!) This photograph shows worn boots returned to a London factory during WW1 to be repaired and sent back to the front.
Likely taken from fallen soldiers, they reflect both wartime necessity and the heavy human cost of war.

No data, no exactly location: a Brit soldier sitting in the mud on the Western Front eating a spoonful of hot food, possibly a potato, from a steaming food container.

The silhouette left on the ground by the body of a crew member of a German zeppelin shot down over the town, who fell from the airship, is observed by British members. Billericay, Essex, Sept 1916

British Mark I tank at the Battle of Somme

Battle traffic seen at Grevillers on 25 August 1918, following the village’s capture by the British 37th Division and the New Zealand Division at the start of the Hundred Days Offensive.

Eric Wookey, of the Gloucester Regiment, wearing an early gas mask and holding a pint outside his billet/1916

Elsie Knocker (1884/1978) and Mairi Chisholm (1896/1981) —known as “The Madonnas of Pervyse”—ran one of the most extraordinary first aid posts of WW1.
In Nov 1914, Elsie and Mairi set up their own frontline aid post in Pervyse, Belgium, treating wounded soldiers just yards from the fighting. Working under constant fire and risking their lives daily, they remained there until 1918, leaving only after being severely gassed.
Their courage and dedication saved countless lives, earning them the Belgian Order of Leopold (1915) and the British Military Medal (1917).

Royal Naval Division troops at Gallipoli, 1915 (Ernest Brooks)

Voluntary Aid Detachment (VAD) ambulance drivers maintaining motor ambulances at Étaples during the First World War.