text: sm ub - 12 sm ub - 12 was a german type ub i submarine or u - boat in the german imperial navy ( german : kaiserliche marine ) during world war i. the submarine disappeared in august 1918 . ub - 12 was ordered in october 1914 and was laid down at the ag weser shipyard in bremen in november . ub - 12 was a little under 28 metres ( 92 ft ) in length and displaced between 127 and 141 tonnes ( 125 and 139 long tons ) , depending on whether surfaced or submerged . she carried two torpedoes for her two bow torpedo tubes and was also armed with a deck - mounted machine gun . ub - 12 was broken into sections and shipped by rail to antwerp for reassembly . she was launched and commissioned as sm ub - 12 in march 1915 . ub - 12 spent her entire career in the flanders flotilla and sank 22 merchant ships , about half of them british fishing vessels . the u - boat was also responsible for sinking the british destroyer hms laforey in 1917 . by early 1917 , ub - 12 had been converted into a minelayer with the replacement of her torpedo tubes with four mine chutes . ub - 12 disappeared after 19 august 1918 . design and construction after the german army 's rapid advance along the north sea coast in the earliest stages of world war i , the german imperial navy found itself without suitable submarines that could be operated in the narrow and shallow seas off flanders . project 34 , a design effort begun in mid - august 1914 , produced the type ub i design : a small submarine that could be shipped by rail to a port of operations and quickly assembled . constrained by railroad size limitations , the ub i design called for a boat about 28 metres ( 92 ft ) long and displacing about 125 t ( 123 long tons ) with two torpedo tubes . ub - 12 was part of the initial allotment of seven submarines — numbered ub - 9 to ub - 15 — ordered on 15 october from ag weser of bremen , just shy of two months after planning for the class began . ub - 12 was laid down by weser in bremen on 7 november . as built , ub - 12 was 27 . 88 metres ( 91 ft 6 in ) long , 3 . 15 metres ( 10 ft 4 in ) abeam , and had a draft of 3 . 03 metres ( 9 ft 11 in ) . she had a single 59 - brake - horsepower ( 44 kw ) körting 4 - cylinder diesel engine for surface travel , and a single 119 - shaft - horsepower ( 89 kw ) siemens - schuckert electric motor for underwater travel , both attached to a single propeller shaft . her top speeds were 7 . 45 knots ( 13 . 80 km / h ; 8 . 57 mph ) , surfaced , and 6 . 24 knots ( 11 . 56 km / h ; 7 . 18 mph ) , submerged . at more moderate speeds , she could sail up to 1 , 500 nautical miles ( 2 , 800 km ; 1 , 700 mi ) on the surface before refueling , and up to 45 nautical miles ( 83 km ; 52 mi ) submerged before recharging her batteries . like all boats of the class , ub - 12 was rated to a diving depth of 50 metres ( 160 ft ) , and could completely submerge in 33 seconds . ub - 12 was armed with two 45 - centimeter ( 17 . 7 in ) torpedoes in two bow torpedo tubes . she was also outfitted for a single 8 - millimeter ( 0 . 31 in ) machine gun on deck . ub - 12 's standard complement consisted of one officer and thirteen enlisted men . after work on ub - 12 was complete at the weser yard , she was readied for rail shipment . the process of shipping a ub i boat involved breaking the submarine down into what was essentially a knock down kit . each boat was broken into approximately fifteen pieces and loaded on to eight railway flatcars . in february 1915 , the sections of ub - 12 were shipped to antwerp for assembly in what was typically a two- to three - week process . after ub - 12 was assembled and launched on 2 march , she was loaded on a barge and taken through canals to bruges where she underwent trials . early career the submarine was commissioned into the german imperial navy as sm ub - 12 on 29 march 1915 under the command of kapitänleutnant ( kapt . ) hans nieland , a 29 - year - old first - time u - boat commander . on 18 april , ub - 12 joined the flanders flotilla ( german : u - boote des marinekorps u - flotille flandern ) , which had been organized on 29 march . when ub - 12 joined the flotilla , germany was in the midst of its first submarine offensive , begun in february . during this campaign , enemy vessels in the german - defined war zone ( german : kriegsgebiet ) , which encompassed all waters around the united kingdom , were to be sunk . vessels of neutral countries were not to be attacked unless they definitively could be identified as enemy vessels operating under a false flag . on 24 july , nieland and ub - 12 sank four british fishing vessels while patrolling between 30 nautical miles ( 56 km ; 35 mi ) east - northeast of lowestoft . all four of the sunken ships were smacks — sailing vessels traditionally rigged with red ochre sails — which were stopped , boarded by crewmen from ub - 12 , and sunk with explosives . ub - 12 similarly sank a pair of smacks off lowestoft on 4 august , and another trio from 23 to 25 august . on 21 november , nieland was succeeded by oberleutnant zur see ( oblt . ) wilhelm kiel in command of ub - 12 . under kiel 's command , ub - 12 sank three ships on 21 february 1916 : the 100 - ton belgian fishing ship la petite henriette , the largest sunk to - date by ub - 12 , and another pair of british smacks , oleander and w.e. brown . ub - 12 sank her largest ship , silksworth hall of 4 , 777 gross register tons ( grt ) , on 10 april . the british - registered ship was en route from hull to philadelphia in ballast when kiel torpedoed her without warning a little more than one nautical mile ( two kilometers ) from the lightvessel . other ships picked up 31 survivors from silksworth hall , but 3 men were lost . later in the month , admiral reinhardt scheer , the newest commander - in - chief of the high seas fleet , called off the merchant shipping offensive and ordered all boats at sea to return , and all boats in port to remain there . grand fleet ambush attempts in mid - may , scheer completed plans to draw out part of the british grand fleet . the german high seas fleet would sortie for a raid on sunderland , luring the british fleet across " ' nests ' of submarines and mine - fields " . in support of the operation , ub - 12 and five other flanders boats set out at midnight 30 / 31 may to form a line 18 nautical miles ( 33 km ; 21 mi ) east of lowestoft . this group was to intercept and attack the british light forces from harwich , should they sortie north to join the battle . unfortunately for the germans , the british admiralty had intelligence reports of the departure of the submarines which , coupled with an absence of attacks on shipping , aroused british suspicions . a delayed departure of the german high seas fleet for its sortie ( which had been redirected to the skagerrak ) and the failure of several of the u - boats stationed to the north to receive the coded message warning of the british advance caused scheer 's anticipated ambush to be a " complete and disappointing failure " . in ub - 12 's group , only ub - 10 sighted the harwich forces , and they were too far away to mount an attack . the failure of the submarine ambush to sink any british capital ships allowed the full grand fleet to engage the numerically inferior high seas fleet in the battle of jutland , which took place 31 may – 1 june . kapitänleutnant georg gerth took command of ub - 12 on 26 june , after oblt . kiel was assigned to command the new minelaying submarine uc - 18 . two months later , admiral scheer set up another ambush for the british fleet with plans for another high seas fleet raid on sunderland ( as had been the original intention in may ) . the german fleet planned to depart late in the day on 18 august and shell military targets the next morning . as in may , ub - 12 was part of a group intended to attack the harwich forces . as one of five boats forming the second line of boats from the flanders flotilla , ub - 12 was stationed off texel by the morning of 20 august . once again , british intelligence had given warning of the impending attack and ambush , causing the grand fleet to sortie at 16 : 00 on 18 august , five hours before the german fleet sailed . faulty intelligence caused scheer initially to divert from sunderland , and then to eventually call off the whole operation . although u - boats to the north sank two british light cruisers , ub - 12 and her group played no part in the action . in september , gerth led ub - 12 in sinking two more ships and capturing a third ship as a prize . the 313 - ton norwegian steamer was sunk on 6 september , while the 55 - ton marjorie was sunk on the 28th . in between the dutch ship niobe was seized as a prize on the 7th . conversion to minelayer ub - 12 and three sister boats — ub - 10 , ub - 16 , and ub - 17 — were all converted to minelaying submarines . ub - 12 was at the dockyard from november 1916 to january 1917 , and it is likely the boat was converted during this timeframe . the conversion involved removing the bow section containing the pair of torpedo tubes from each u - boat and replacing it with a new bow containing four mine chutes capable of carrying two mines each . in the process , the boats were lengthened to 105 feet ( 32 m ) , and the displacement increased to 147 t ( 145 long tons ) on the surface , and 161 t ( 158 long tons ) below the surface . during this same time , kapt . gerth was transferred to sm uc - 61 , and replaced on ub - 12 by oblt . friedrich moecke in early november . moecke was , in turn , replaced by oblt . ernst steindorff in january 1917 . by march , the newly converted submarine had begun laying mines off the french coast . the french navy trawler elisabeth struck one of ub - 12 's mines off calais on 13 march and sank . five days later , the british auxiliary minesweeper duchess of montrose sank with a loss of 12 men after detonating a mine laid by ub - 12 off gravelines . on 23 march , hms laforey , a destroyer with the dover patrol , struck one of ub - 12 's mines off cape gris - nez and went down with the loss of 59 men . in may , ub - 12 was on a patrol with ub - 39 in the english channel . on the night of 14 / 15 may while ub - 12 was on the surface , steindorff noted a large underwater explosion some miles away in a british minefield , and when ub - 39 failed to return to zeebrugge , one of the bases for the flanders flotilla , reported what was likely the demise of ub - 39 at the hands of a british mine . april found two more victims added to ub - 12 's tally . on the 20th , , another british auxiliary minesweeper was lost on one of ub - 12 's mines near the dyck lightvessel . six days later , the british steamer was mined while loaded with pit props destined for dunkirk . the 1 , 744 - ton cargo ship was the largest ship sunk by ub - 12 since the silksworth hall , sunk the previous april . ub - 12 sank another two ships under steindorff 's command , one each in june and july . the steamer dulwich — carrying coal from seaham for london — was mined and sunk with the loss of five men on 10 june . one month later , the french patrol vessel jupiter i was mined off calais . these were the last two ships credited to mines from ub - 12 for the next fourteen months . fate ub - 12 's activities over the next year are not well documented , and no specific record of her can be found in english - language sources . however , it is known that during this period , she was helmed by four different commanders , with the final officer , oblt . ernst , assuming command in may 1918 . under 's command , ub - 12 departed zeebrugge on 19 august to lay mines in the downs off the kentish coast , but never returned . according to one british source , ub - 12 was herself mined off helgoland sometime in august . author dwight messimer considers this unlikely given that helgoland is nowhere near the route that ub - 12 could have taken to get to the downs . a postwar german study concluded the two most likely fates for ub - 12 were that she either struck a british mine or was destroyed by one of her own mines that malfunctioned during deployment . messimer also considers it possible that ub - 12 may have had a diving accident related to her conversion to a minelayer . some two months after ub - 12 's presumed loss , she was credited with the sinking of her final ship . on 27 october , two weeks before the end of the war , the 92 - ton british ship struck one of ub - 12 's mines near the elbow lightvessel and sank . summary of raiding history external links - 12 off ramsgate : marine geophysical survey and archaeological report ' ' historic england project to research first world war