The STEN (or Sten gun) was a family of British 9 mm submachine guns used extensively by British and Commonwealth forces throughout World War II and the Korean War. They were notable for having a simple design and very low production cost making it an effective insurgency weapon with resistance groups. Over 4 million Stens in various versions were made in the 1940s.
STEN is an acronym, from the names of the weapon's chief designers, Major Reginald V. Shepherd and Harold Turpin, and EN for Enfield.
Rolf Mehlen carried a Sten gun when he fought with the German Emergency Militia in West Germany against the invading Soviets during World War III. He fought with reckless courage, charging a Soviet machine-gun nest while firing the Sten to keep his opponents heads down, then finishing them off with grenades. His colleague Gustav Hozzel was both impressed and appalled by this display of courage.
When Sgt. Alistair Walsh served in Egypt in 1942, he made sure to carry a Sten gun. While cheaply made and likely to fall apart if dropped, it would spray a lot of bullets which was what Walsh wanted and needed during a fight. After he was wounded and returned to service, this time by Calais, Walsh continued to cary a Sten. It didn't have the range of a rifle but for the house-to-house fighting he expected, the higher rate of fire would more than compensate.