[1] The Ronis-class submarines were propelled by two shafts driven by two Sulzer diesel engines for travel on the surface, rated at 1,300 brake horsepower (970 kW) and two electric motors 700 shaft horsepower (520 kW) for subsurface movement.

They were armed with six 21-inch (533 mm) torpedo tubes with two located in the bow, and four situated in two twin external turnable mounts.

[3] Constructed in France, the submarines were part of the navy's plan to guard Latvia's coastlines.

During World War II, the Ronis-class submarines participated in operations in the Baltic Sea.

However, with the Germans approaching the city, the Soviets were forced to blow up and scuttle the Ronis-class submarines on 24 June 1941 to prevent their capture.