Merchant submarine
They were constructed to slip through the naval blockade of the Entente Powers, mainly enforced by the efforts of the United Kingdom's Royal Navy.
[2][circular reference] Britain soon protested with the US against the use of submarines as merchant ships, arguing that they could not be stopped and inspected for munitions in the same manner as other vessels.
[3] On its first journey to the US, departing on the 23 June 1916, Deutschland carried 163 tons of highly sought-after chemical dyes, as well as medical drugs and mail.
[2][circular reference] A second journey in October-December of the same year was also successful, again trading chemicals, medicines and gems for rubber, nickel, alloys and tin.
[2][circular reference] Following his return, captain Paul König wrote a book (or possibly had it ghostwritten) about the journeys of Deutschland.
The declaration of war had been partly due to US anger over the actions of German submarines sinking shipping bound for Great Britain, sometimes just outside American territorial waters (See SM U-53).
Its fate was never decisively uncovered, though she may have collided with the British armed merchant cruiser HMS Mantua south of Iceland, as was theorized after the war.
As these boats were part of Kriegsmarine (Nazi Germany's navy), did carry light armaments (anti-aircraft guns), and never engaged in trade as such, they do not qualify as merchant submarines.
After the Italian submarines were converted for this cargo role, most of the extended range design were completed as an armed type IXD2 variant.
These were the 880-ton Archimede, the 940-ton Barbarigo, the 951-ton Comandante Cappellini, the 1,030-ton Alpino Bagnolini and Reginaldo Giuliani, the 1,036-ton Leonardo da Vinci and Luigi Torelli, the 1,331-ton Enrico Tazzoli and Giuseppe Finzi, and the 1,504-ton Ammiraglio Cagni.
[9] Following the Italian armistice in September, Giuseppe Finzi and Alpino Bagnolini were seized by Germany while undergoing conversion at Bordeaux, and designated UIT-21 and UIT-22, respectively.
UIT-22 departed Bordeaux for Sumatra in January 1944 and was destroyed by RAF 262 Squadron Catalina bombers off South Africa in March.
These would not strictly count as merchant submarines, as they would have been at least lightly armed and used mainly for directly war-related duties, such as supplying troops or delivering military forces to their targets.
In World War II, the Soviet Union used submarines (as well as other ships) to supply the besieged Crimean port of Sevastopol.
No weapons beyond two deck guns were envisaged, and the design borrowed many existing parts from the earlier VI and VI-bis submarine series to simplify construction.
[12] In the 1990s, the Malachite design bureau in St. Petersburg proposed submarines capable of transporting petroleum or freight containers in or through Arctic regions.
Mostly it was regarding to the vital supply of aluminum from South and Central America via submarines to avoid being sunk by enemy U-boats.
Financial limitations of the Great Depression made this early attempt less successful than the post-war accomplishments of a nuclear-powered submarine of the same name; USS Nautilus (SSN-571).
[15] Similar to the post-Cold War ideas of the Russian Federation, there have been some concept plans to use atomic-powered submarine oil tankers to exploit Arctic oilfields in Alaska and Siberia.
In one case, a Colombian drug cartel was interrupted before finishing the construction of a professional-grade, 30 m long, 200 ton carrying-capacity submarine apparently intended for the cocaine trade with the US.
