Merchant submarine

A merchant submarine is a type of submarine intended for trade, and being without armaments, it is not considered a warship like most other types of submarines. The intended use would be blockade running, or to dive under Arctic ice.

Strictly speaking, only two submarines have so far been purpose-built for non-military merchant shipping use, outside of criminal enterprises, though standard or partly converted military submarines have been used to transport smaller amounts of important cargo, especially during wartime, and large-scale proposals for modern merchant submarines have been produced by manufacturers. Criminal enterprises have also built transport submarines to avoid authorities, such as narcosubs.

Germany

Only two merchant submarines have historically been built, both in Germany during World War I. They were constructed to slip through the naval blockade of the Entente Powers, mainly enforced by the efforts of Great Britain's Royal Navy. The British blockade had led to great difficulties for German companies in acquiring those raw materials which were not found in quantity within the German sphere of influence, and thus was hindering the German war efforts substantially.