'EB' was a British naval operation to seize the German weather vessel München and its important code equipment and documentation (5/7 May 1941).
After Enigma-coded signals from a weather observation and reporting vessel had been intercepted by British D/F stations, which were thus able to establish the position of the sending vessel, the light cruisers Birmingham, Edinburgh and Manchester of the 18th Cruiser Squadron, under the command of Vice Admiral L. E. Holland, departed Scapa Flow in the Orkney islands group during 5 May, and on the following day were joined to the east of Iceland by the destroyers Bedouin, Eskimo, Nestor and Somali. The entire force then headed to the north in the direction of the weather vessel’s position near Jan Mayen island.
At 15.00 on 7 May, just inside the Arctic Circle, the British ships were deployed at 10-mile (16-km) intervals in their search for München. The plan was to employ surprise and speed to capture the vessel in the hope of securing the coding tables before the Germans had been able to jettison them over the side in weighted containers.
At 17.07 the German vessel was spotted between Edinburgh and Somali. The latter fired warning shots, and München's crew began to abandon ship. Somali went alongside and took possession of the vessel, and then a prize crew from Edinburgh arrived in a cutter, which also carried Captain J. R. S. Haines of Naval Intelligence, in civilian clothes. München's captain had thrown the Enigma coding machine over his vessel’s side as Somali approached, but had left the coding tables for May and June on his desk, and these were seized by Haines.
Some of München's crew were taken on board Somali, but most were accommodated in Edinburgh, which reached Scapa Flow on 10 May. Somali escorted the captured vessel to Scapa Flow, and Nestor delivered Haines back to Scapa Flow at high speed.
From the Orkney islands Haines was immediately flown to London with the vital documents.
The rest of the task force continued north in search of another German weather ship believed to be operating within the Arctic Circle. Although the search was continued to the edge of the ice field, and Supermarine Walrus spotter flying boats were used, the other German vessel was not located. As München had radioed a sighting report, it is probable that the other ship had moved off to the east. The British subsequently used the cover designation 'Primrose' (ii) to conceal the real nature of 'EB'.
Although 'EB' had no direct result in the British search for the German battleship Bismarck during her 'Rheinübung' sortie into the Atlantic, the fruits of the information discovered on München and U-110, on 7 and 10 May respectively, allowed the Royal Navy between 3 and 18 June to undertake a systematic search for and either destroy or sink many of the ships of the German raider supply organisation, and during this effort a number of Axis blockade-runners at sea were also lost.
On 28 May the 3,290-ton blockade-runner Lech, homeward-bound from Rio de Janeiro, was scuttled by her crew in the South Atlantic when a British warship approached here. On the following day the weather ship August Wriedt fell victim to the British search operations. On 3 June the 6,367-ton tanker Belchen, which had replenished U-111 and U-557 in the Davis Strait between Greenland and Baffin island, was caught and sunk by the British light cruisers Aurora and Kenya between Greenland and Labrador, the German survivors being rescued by U-93.
On 4 June the 8,923-ton tanker Gedania was abandoned after her crew had sighted the approach of the 4,890-ton British armed boarding vessel Marsdale, whose crew was therefore able to take possession of the tanker without opposition. An aircraft from the fleet carrier Victorious, proceeding to Gibraltar with the light cruiser Hermione, sighted the 4,000-ton patrol ship Gonzenheim to the north of the Azores islands group, but the German ship was able to escape from the 14,204-ton auxiliary merchant cruiser Esperance Bay before being scuttled when the battleship Nelson and light cruiser Neptune, called to the scene, came into view: Neptune torpedoed the burning wreck.
On 4 and 5 June respectively the tankers Esso Hamburg (9,849 tons) and Egerland (9,798 tons) were scuttled by their crews in the South Atlantic supply area along the route linking Freetown, Sierra Leone, and Natal, Brazil, when they were approached by the heavy cruiser London and destroyer Brilliant.
On 6 June the 9,179-ton blockade-runner Elbe, homeward-bound from the Far East, was sunk by aircraft from the fleet carrier Eagle near the Azores islands group.
On 8 June Vice Admiral Sir James Somerville’s Force 'H' (battle-cruiser Renown, fleet carrier Ark Royal, light cruiser Sheffield and six destroyers) departed Gibraltar to the west to avoid Vichy French air attacks anticipated in response to the 'Exporter' seizures of Lebanon and Syria, and also to effect the interception of German supply ships and blockade-runners. On 9 June Force 'H' met the fleet carrier Victorious, steaming south with the light cruiser Hermione, and Sheffield was detached to return to the UK. On 12 June Sheffield encountered the homeward-bound 10,397-ton Friedrich Breme in the North Atlantic to the west-north-west of Cape Finisterre, and the crew of this German tanker scuttled their ship.
On 15 June the supply ship Lothringen, tasked with the replenishment of the U-boats operating off Sierra Leone, was sighted in the central Atlantic by an aeroplane from the fleet carrier Eagle and then captured by the light cruiser Dunedin.
As the British search groups were replenishing and Force 'H' was operating in the Mediterranean, the Axis powers were able to pass the patrol ship Kota Pinang, the supply ships Ermland and Spichern, the Italian blockade-runners Atlanta and Todaro all homeward bound past West Africa, and the German Regensburg homeward-bound from the Far East all passed through the blockade line to reach ports on the west coast of France.
On receiving information that more ships had been sighted, Force 'H' once again headed into the Atlantic on 16 June with Renown, Ark Royal, Hermione and the destroyers Faulknor, Fearless, Forester, Foresight and Foxhound. The destroyers located and sank Oberleutnant Franz Gramitzky’s U-138, which was the only U-boat operating in the area, on 18 June and then departed to refuel at Gibraltar.
After another unsuccessful search, the other ships of Force 'H' returned to Gibraltar on 21 June.
On the same day the appearance of the heavy cruiser London persuaded the captain of the 4,422-ton German blockade-runner Babitonga, homeward-bound from Brazil, to scuttle his ship in the South Atlantic.
During the afternoon of 22 June British air reconnaissance sighted the 3,039-ton supply ship Alstertor, which was returning from the Indian Ocean, and the boarding vessel Marsdale and the destroyers Faulknor, Fearless, Forester, Foxhound and Fury were despatched to search for her. On 23 June, off Cape Finisterre, the crew of Alstertor sighted the British warships and her captain decided to scuttle his ship: the British ships rescued the crew and 78 British prisoners transferred from the German merchant raider Atlantis.
Six of the eight German ships sunk between 3 and 18 June were lost as a result of the British penetration of German naval Enigma traffic, and another seven supply ships and weather vessels succumbed for the same reason in the course of the following three weeks. The Admiralty then decided to end the effort in case German naval intelligence came to the conclusion that the British were indeed reading encrypted naval signals.