STEN is an acronym for the designers Shepard, Turpin and Enfield, the manufacturer. In 1940, after the disaster at Dunkirk and facing the prospect of a German Invasion, the British needed weapons and they needed them fast. The answer was the Sten gun, a simple design that was cheap and fast to produce compared to the American Thompson or the German MP40. During the war more than 4 million were produced, the most common variant was the Mk.2. The gun was issued to British and commonwealth forces. It was also smuggled in to occupied countries were it was used by various resistance movements. It Was so simple to produce that several resistance movements managed to manufacture it in secret.
One Variant of the gun featured an integrated suppressor. This was used by special forces such as the SAS on covert missions. Later variants of the Sten were of higher quality, but the Mk.2 which was the most common was not well liked by the troops, it was known for its bad reliability and cheap look. The gun would often jam and was known to accidentally discharge. However due to economic reasons it would continue to be used into the 60's.