A soldier looking through a trench periscope, 1916 (c)

Photograph, World War One, Mesopotamia (1914-1918), 1916 (c).

Periscopes provided a less dangerous way of observing the Turks from the trenches. In its simplest form, a periscope could be just a stick with two angled pieces of mirror at the top and bottom.

From one of five photograph albums compiled by Lieutenant Kindom.