Germany hesitated for a long time to build submarines, seeing them as purely defensive naval warfare devices. It was not until 1906 that the first fully functional German submarine „U1“ was put into service.
With „U5“ to „U12“ however, the Imperial Navy already had submersibles 4 years later that were far superior to foreign competitors. The first diesel-powered submarines were produced as early as 1913 („U19“ to „U22“).
During World War I, it quickly became clear that submarines were the only means of naval warfare that could break the British blockade. However, large-scale production (as later in World War 2) did not take place. The Versailles Peace Treaty of 1919 stipulated the extradition of 176 submarines and prohibited the German Reich from building and maintaining submarines.