The Submarine War Steamer St Margaret, sunk 1917. Shetland Museum The Germans regarded their U-Boats as a submersible counter-blockade. The submarine hadn’t been significant in naval warfare before World War One. Its potential was unknown but feared, especially in regard to warships. On 22 September 1914, the German submarine U-9 sank the old British cruisers, Aboukir, Cressy, and Hogue, in a single action. However, the main use of Kaiserliche Marine submarine fleet was against allied merchant shipping. Britain depended heavily on its merchant fleet, and Shetland contributed manpower disproportionately to that same fleet. Not only that, but the islands’ links with the rest of the UK were solely by sea. The allies blockaded Germany with surface vessels. The Germans regarded their U-Boats as a submersible counter-blockade. They would use the novel technology to interdict allied supplies, and degrade the war economy of Britain especially. Adding quick firing guns to U-Boats and leaving the limited supply of torpedoes for high value targets made a very effective weapons system. They were also important mine-layers. Actions against merchant shipping had to be undertaken under the rules of war. Vessels had to be stopped, searched and, if need be, sunk. But submarines could be much more effective if they sank vessels on sight. For periods during World War One, Imperial Germany operated unrestricted submarine warfare, where civilian vessels were sunk without warning. Often this was by gunfire. For most of 1915 this policy operated in the North and Irish Seas. It was suspended on 1 September that year. An attack on the ferry ss Sussex had outraged international opinion. It operated again from 15 March to 20 April 1916. Unrestricted warfare resumed at the beginning of February 1917, and just short of 700,000 tons of allied and neutral shipping was lost in April that year. Thereafter the total declined and U-Boat losses rose. The Germans never had the number of submarines of sufficient size and range to truly effect the devastation needed. The allies developed counter-measures, mainly convoys, but also patrols by aircraft and mine barrages, and weapons such as depth-charges. Shetland lost a great deal of men through this kind of warfare. The war memorial lists 121 merchant seamen dead. While this total includes death by accident and illness, and by mine, much of it is attributable to the U-Boat campaign. The Roll of Service shows 140 seamen who survived mining or torpedoing. More info: James Scott, sunk by gunfire January 1916. Captain William Leask, torpedoing of St Margaret, Sept. 1917. Charles Hardy, ss Euphorbia, torpedoed July 1916. Unknown sailor, torpedoed for the second time, Feb. 1918. Captain Henry Mainland, ss Lanao, sunk Oct. 1916.