STEN is an acronym of - Major R.V. Shepherd, Mr. Harold Turpin & the Royal Small Arms Factory, Enfield. Shepherd & Turpin are the credited designers of the weapon and Enfield the manufacturers although Stens were produced in Canada and hand made by Partisans in some countries. The need for a cheap Sub-Machine Gun was made clear after America's entry in to the war in 1941 when Britain was buying up all the available Thompsons it could get it's hands on. This put a strain on Thompson production and so the Sten came along at just the right time. Easy to manufacture it was made of Stamped Metal Parts that were welded together to make the basic shape with other components added afterwards. In it's most basic version (Mk III) it only had 47 working parts. About 4 million Stens were produced seeing service in to the Korean war. Many Partisans even made their own copied versions with about 2500 of these seeing use in Poland during the Warsaw uprising. It became a standard British Army weapon from 1942 and equipped most Infantry Units.