Submarine Warfare - World War I

World War I

Submarine warfare in World War I was partly a fight between German U-Boats and Atlantic supply convoys bound for Great Britain. British and Allied submarines conducted widespread operations in the Baltic, North Sea, Atlantic, Mediterranean and Black Seas. Only a few actions occurred outside of the wider European-Atlantic theatre. German submarine attacks on allied merchant ships gave a direct cause for Americans to enter the war in April 1917.

All participants were supposed to abide by the Hague Conventions of 1899 and 1907 but this was found to be impracticable for submarines. Initially German submarines did attempt to comply with the Prize Rules but then went to unrestricted submarine warfare. American diplomatic pressure forced the Germans to stop this for a while, but in January 1917 Germany declared a War Zone around the British Isles and sank up to a quarter of shipping entering it, until escorted convoys were introduced. The sinking of the Pathfinder was the first combat victory of a modern submarine, and the exploits of U-9, which sank three British cruisers in under an hour, establishing the submarine as an important new component of naval warfare.

German submarines were used to lay mines and to attack iron ore shipping in the Baltic. The British submarine flotilla in the Baltic operated in support of the Russians until the Russian-German Pact.

During the war, the British invested efforts in developing a submarine that could operate in conjunction with a battleship fleet - the "Fleet Submarine". To achieve the necessary 20 knots (surfaced) the K class submarines were steam powered. In practice the K class were a constant problem and could not operate effectively with a fleet.