A British sentry keeps watch at a trench junction entitled 'Courlay Trench' and 'Gordon Alley', 1917 (c)

Photograph, World War One, Western Front (1914-1918), 1917 (c).

Trenches were not dug randomly, but were part of a complex design. Each of the front line trenches was backed-up by second and third lines: 'support' and 'reserve' trenches. Communication trenches linked them all together. The support and reserve trenches were lined with underground shelters or dug-outs which were used as protection from enemy fire and the weather. To help with navigation, trenches were named after well-known streets in the soldiers' home towns. Signposts were put up and trench maps made.

Official photograph from an album relating to the Western Front.