The action off Lerwick (, "Lerrick") was a naval engagement on 17 October 1917 fought in the North Sea during the First World War. The German light, minelaying cruisers and attacked a westbound convoy of twelve colliers and other merchant ships and their escorts, part of the regular Scandinavian convoy. The two escorting destroyers and nine neutral Scandinavian ships were sunk off Shetland, Scotland.
Admiralty code breakers had uncovered the call signs of Bremse and Brummer and by direction finding knew that they had sailed from Wilhelmshaven to (Lister Deep) north of Sylt but an operation as far north as the Scandinavian convoy collier route was not anticipated by the British naval commanders because the Admiralty failed promptly to pass on the information.
Both of the British destroyer commanders were commended for their bravery, though some members of the Admiralty felt that by leaving the convoy to engage a superior enemy force, they had left the merchant ships open to attack. Other British ships did not receive reports of the attack until late afternoon, were not in a position to intercept and the German cruisers returned safely to port. The British called the attack on neutral vessels, giving no time for the crews to abandon ship, an outrage.
The Germans denied allegations that their ships had fired on survivors in the water, despite the evidence of gunshot wounds to some crewmembers. Admiral David Beatty, the commander-in-chief of the Grand Fleet, severely criticised the Admiralty for failing to pass on information derived from the code-breakers of Room 40.
Background Neutral shipping The German U-boat campaign inflicted serious losses on neutral shipping but British counter-measures along the east coast of Britain and in the North Sea, including escorted convoys, managed to limit the losses of Scandinavian merchant ships. British losses continued unabated and in the last three months of 1916 losses of 618,000 gross register tons (GRT) were matched by only 220,000 GRT of new ships. From January to March 1917, 912,000 GRT were lost for a replacement of 326,000 GRT. Neutral shipping was an important addition to the British merchant fleet but in the last quarter of 1916, non-British shipping losses, excluding those of the Central Powers were 1, 159,000 GRT and in the next three months were 1,619,000 against new building of 587,000 GRT (mostly US construction). British ships were being fitted with defensive armament, often a 4.7-inch gun with a naval crew. Neutrals were afraid to arm their ships and compromise their status as non-combatants, making them more vulnerable than the British ships.
Norway
In February 1917, the British government took soundings with several neutral governments over the purchase of their merchant fleets but the suggestion was spurned. In negotiations with the Norwegian government about the resumption of coal imports from Britain, the Norwegians were so desperate for coal that they offered the merchant fleet if the matter could be carried off without German reprisals. The suggestion was all the more compelling to the Norwegians because the British could requisition their ships with no provision for any supplies to Norway. In June 1917, about 300,000 people protested against rising food prices, 40,000 in the capital, Kristiania. The Norwegian prime minister, Gunnar Knudson, thought that another coal shortage would cause mass unemployment, social unrest and possibly revolution. It was suggested that rather than sell the fleet, the Norwegians should charter it and that armed British ships be substituted on the routes suffering the worst losses from German U-boats. The Norwegian Shipowners' Association () accepted the Tonnage Agreement in which the transport of coal to Norway would be assured by British charter or requisition of the ships. The connivance of the Norwegian government in the arrangement would be camouflaged by being made by the and the Ministry of Shipping. The British gained 130 freighters of 200,000 GRT and the Norwegians of coal per month.
The Scandinavian convoy In April 1917, the British began shipping coal north from the Humber Estuary to Lerwick in the Shetland Islands and then across the North Sea to Norway. Beginning in autumn 1914, six minesweeping trawlers sailed from each port on the east coast just before dawn and swept a channel wide and long, the sweep being repeated late in the day. The swept channel was extended northwards to Scotland and the Orkney Islands. The monthly quota of required daily convoys from Lerwick, most being neutral Scandinavian ships, usually escorted by two British destroyers from a pool of eight detached from the Grand Fleet, supported by several armed trawlers. To 1 July, 351 ships made the eastbound journey from Lerwick and 385 the voyage westwards from Norway, an average of 368 round trips a month, for the loss of twenty ships. In July, ten ships were sunk by the attacks of , , , and , from 454, a loss of 2.2 per cent. Seven depth charge attacks were made by escort ships to no effect and was torpedoed while escorting colliers northwards up the British coast to Lerwick. In anticipation of the added difficulty of escorting colliers in the autumn, winter and spring, several cruisers were sent to the Humber. The Scandinavian convoys had been a considerable success but had to sail in waters where they were vulnerable to German surface vessels for most of the journey. The return voyage began in Bergen in Norway, a neutral port where sailings could be observed by Germans and the use of neutral ships made it impossible for the British to keep convoy procedures and sailings secret.
Net mine barrage Earlier in 1917, the Admiralty anticipated that U-boats would soon return to Germany. In early October 1917 another attack was planned. U-boats sailed between two minefields to the east of the Dogger Bank and the Outer Silver Pit, a funnel in the North Sea long, wide at the north end, narrowing to at the southern end. A barrage of underwater mine nets were to be laid at the narrow end of the funnel. At the wide (northern) end, four submarines mounted a standing patrol and further south, two destroyer leaders, fourteen destroyers and a yacht patrolled between the Moray Firth and the Firth of Forth. Net drifter fishing boats, were to place nets in the funnel between the Firth of Forth and Flamborough Head. Four destroyers and sixteen trawlers, commanded from the yacht, HMY Goissa. The southernmost end of the funnel, where U-boats had to skirt the Dogger Bank minefields, was to be patrolled by Harwich Force. To maintain the standing patrols required between destroyers and flotilla leaders, with from Harwich Force, beginning on 27 September.
Storms interrupted the operation several times and the submarines, patrol ships and net barrage boats saw nothing of note during the operation. The net drifters reported nine underwater explosions as the nets were being strung out. The explosions were taken to be premature explosions of mines catching in the nets. As dark fell more explosions were heard, two green rockets were spotted at the east end of the net line and more explosions were heard. On 3 October, hydrophones detected a submarine at the west end of the nets, an explosion and then silence; other boats' hydrophone sets gave similar indications. There was silence until 9 October, when the destroyer was attacked north of the net barrage. Before the U-boat was expected to reach the nets, another was seen and attacked, then a U-boat engine was heard clearly and a depth charge dropped. The weather had damaged the nets and mines and on 10 October the operation was terminated. The Director of Naval Intelligence reported a month later that three U-boats had been destroyed close to the mine trap; German sources later confirmed that , and had been sunk.
Prelude
High Seas Fleet
During late 1917, the commander of the High Seas Fleet, () Admiral Reinhard Scheer, decided to augment the U-boat campaign with attacks on the Scandinavian convoys by surface ships. Scheer hoped to terrorise Scandinavian neutrals, who were co-operating with the British and sailing in convoys with naval escorts. Scheer anticipated that success would force the British to divert naval ships from counter-U-boat operations and create an opportunity to engage the Grand Fleet at an advantage. U-boat reports gave the impression that much shipping was moving between Lerwick and Bergen in Norway. German bases to the south of the route made a surprise attack at the east end of the convoy route by surface ships feasible. The short days and stormy weather in the autumn and winter increased the possibility that a sortie could go unobserved.
By forcing the British to reinforce the escorts of the Scandinavian convoy, a surface ship attack could help the wider U-boat campaign. The new, fast, minelaying light cruisers Brummer ( Max Leonhardi) and Bremse ( Siegfried Westerkamp), with a speed of , each armed with four naval guns and two (22-pounder) anti-aircraft guns, were chosen for an operation against the Scandinavian convoy. The minelaying gear was taken off and the ships disguised to look like British C-class cruisers. Brummer and Bremse kept wireless silence and Brummer had a wireless interception team on board to jam British signals. On 17 October, a westbound convoy of two British, one Belgian, and nine Scandinavian ships was off Lerwick.
Room 40
In this section, the course of British code breaking and communication between the Admiralty, Beatty and ships at sea has anticipated events for continuity.
On 15 October, Room 40 decrypted a message from Brummer that "Most Secret Order 71950" had been put back to 16 October. The message contained notice that the ship would sail via Norman Deep, because Way Blue had been blocked by mines, asking that minesweeping be carried out. An hour later, Admiral Sir Henry Oliver, the Deputy Chief of the Naval Staff, dispatched a signal to Beatty, "Minelayer Brummer leaves via Norman Deep tomorrow 16 to northward probably for minelaying. She should be intercepted". More decodes became available to Oliver soon afterwards and should have suggested that minelaying might not be the reason for the sortie; wireless silence was unusually rigorous and a decoded message from the submarine described much shipping off Lerwick. Late on 16 October, the light cruiser reported that it would be off List auf Sylt at the north end of the island of Sylt with destroyer escorts, corresponding to a signal from Brummer that afternoon. Signals were then decrypted ordering all U-boats to refrain from attacks on light cruisers, except when certain that they were British. Oliver had undertaken to pass on new data to ships at sea but failed to supply this, the inferences that could be drawn from them or to contact Beatty until eighteen hours later, by when the convoy had been attacked.
15 October convoy