Her pre-war service was uneventful, as she trained crews and officers in the rapidly expanding U-boat arm of the Kriegsmarine following the abandonment of the terms of the Treaty of Versailles two years before.

The submarine was powered by two MWM RS 127 S four-stroke, six-cylinder diesel engines of 700 metric horsepower (510 kW; 690 shp) for cruising, two Siemens-Schuckert PG VV 322/36 double-acting electric motors producing a total of 460 metric horsepower (340 kW; 450 shp) for use while submerged.

[1] During the Second World War, she was mainly deployed for coastal work, a role enforced by her small size and endurance.

It was in this region that she scored her first successes, after fruitless operations off the Polish coast during the invasion of that country and a patrol against British shipping coming from Norwegian ports.

In December 1940 she laid mines off Blyth, in Northumberland, which claimed two coastal freighters and a naval patrol minesweeper in less than a week.