In the trench warfare of the First World War, exposing even a helmet above the parapet could draw immediate enemy fire. The trench periscope allowed soldiers to observe no-man’s-land and enemy positions while remaining safely below the trench line.
This example is a box-type trench periscope made by W. Watson & Sons, Ltd.. It consists of a rectangular wooden case fitted with two flat mirrors set at 45-degree angles, creating a simple optical path that relays the forward view down to the observer. Viewing openings at the top and bottom allow observation while remaining under cover.
Trench Observation and Soldier Safety
After late 1914, static trench systems dominated the Western Front. Enemy lines were often close, and snipers and machine-gunners watched constantly for movement. Observation was essential but dangerous, making trench periscopes a common and effective safety device used by sentries, officers, and infantrymen alike.
Early trench periscopes were made by installing two mirrors at 45-degree angles at either end of a long box or tube. During the winter of 1914–1915, soldiers on the front lines used these improvised box periscopes, also known as hyposcopes. Most measured between 30 centimetres and 100 centimetres in length.
In early 1915, commercial manufacture of box-type trench periscopes began in the United Kingdom. However, demand exceeded supply until 1916. To make up for the shortfall in commercial supply, British Army workshops behind the front lines started to manufacture trench periscopes in mid-1916.
Construction and Use
Periscopes of this type used no lenses. Light entering the top opening was reflected downward by the upper mirror and redirected toward the observer by the lower mirror. While the image was reversed and lacked magnification, it was sufficient for detecting movement and observing enemy activity.
These periscopes could be rested on the parapet or braced against sandbags. Their simple wooden construction made them inexpensive, lightweight, and easy to replace.When observing with a binocular, rest it on the glass screen. When observing without a binocular, lower the shutter until the eyes are protected by it and the glass screen.
Technical Summary
- A 3.25 inch (8.26 cm) deep by 4.5 inch (11.43 cm)wide by 13 inch (33.02 cm) high grey wooden box with a 45 degree mirror at either end with a 3 inch (7.62 cm) by 4 inch (10.16 cm) viewing slot on each end.
- Construction: Wooden box with flat glass mirrors
- Periscope No. 9. Mark II with 22.5 inches between mirrors) TRENCHSCOPE CO 1917.