The STEN, or Sten gun, is the name given to a family of blowback-operated British submachine guns chambered in 9×19mm Parabellum. They were used extensively by both British and Commonwealth forces throughout World War II and the Korean War. The word "Sten" is an acronym, and was created from the names of the weapon's chief designers: the "S" comes from Major Reginald V. Shepherd, the "T" from Harold J. Turpin, and the "En" stands for the Enfield factory.