Sten

The STEN (or Sten gun) was a family of British submachine guns chambered in 9×19mm and used extensively by British and Commonwealth forces throughout World War II and the Korean War. They had a simple design and very low production cost, so they were also effective insurgency weapons for resistance groups.

STEN is an acronym, from the names of the weapon's chief designers, Major Reginald V. Shepherd and Harold Turpin, and EN for Enfield. Over four million Stens in various versions were made in the 1940s.