sentences:  Soviet S-class submarine
  
  The S-class or Srednyaya (, "medium") submarines were part of the Soviet Navy's underwater fleet during World War II.Unofficially nicknamed Stalinets (, "follower of Stalin"; not to be confused with the submarine L-class L-2 "Stalinets" of 1931), boats of this class were the most successful and achieved the most significant victories among all Soviet submarines.