- Disrupting Supply Lines
- Anti Surface Ship Warfare
- Mine laying
- Aiding and Moving Covert Agents
- Aiding and Moving Military Forces
- Gathering Intelligence
- Rescuing Downed Air Men
- "Milk Cowing" Resupplying Other Submarines
- Carrying Cargo
- And Occasionally Attacking Other Submarines.
Photograph from the periscope of USS Thresher (SS-200) in January 1944, of a torpedoed Japanese merchant ship sinking in the Pacific. Courtesy National Archives.