Constructed by DeSchiMAG AG Weser in Bremen as yard number 903, U-25 was commissioned on 6 April 1936.

It experienced a short, but successful combat career, sinking eight ships and damaging one.

During its trials it was found that the Type IA submarine was difficult to handle due to its poor stability and slow dive rate.

In early 1940, the boat was called into combat duty due to the shortage of available submarines.

Enid (Captain Wibe), of then-neutral Norway en route to Dublin, went to assist Polzella.