A periscope rifle is a rifle that has been adapted to enable it to be sighted by the use of a periscope. This enables the shooter to remain concealed below cover. The device was independently invented by a number of individuals in response to the trench warfare conditions of the First World War, and while it is not clear which army was the first to use periscope rifles, the weapons were in use by the end of 1914.[1]
Similar devices were also built for use with machine guns.[2][3] In 1916, another similar device was patented for use with pistols.[4]