Battle of Atlantic - May-June 1941 , Codebreaking , US Intervention in Atlantic , Allied Shipbuilding and German Surface Raiders and Capture of Enigma Machine (part 2)

Hitler’s U-Boat War” , Clay Blair Jr.
“The War For All Seas” , Ewan Mawdsley
“World War II At Sea” , Craig L. Symonds
“The War With Hitler’s Navy” , Adrian Stewart

The loss of Bismarck marked a turning point in the German naval war. Its humiliating failure, together with the failure of the battle cruisers Gneisenau and Scharnhorst to inflict any substantial damage on British maritime assets, brought to a close the dominance of the big surface ships in the Kriegsmarine. Never again was one to sortie into the Atlantic. Virtually overnight the U-boat became the Kriegsmarine’s preferred ship, the only possibility for defeating Great Britain at sea. Admiral Raeder’s influence on Hitler declined; that of Dönitz rose commensurately.

In US , President Roosevelt seized upon the Bismarck sortie to nudge the United States closer to open intervention. On May 27, the day Bismarck went down, he legally declared a state of unlimited national emergency. “The Battle for the Atlantic,” Roosevelt said somewhat expansively, “now extends from the icy waters of the North Pole to the frozen continent of the Antarctic.” Everything pointed to an eventual attack on the Western Hemisphere. “It would be suicide to wait until they are in our front yard,” he concluded. Therefore he had ordered the US Army and Navy to intensify air and surface-ship patrols in the North and South Atlantic and had directed the U.S. Maritime Commission to dramatically increase the production of merchant shipping. Two weeks later, he froze German and Italian assets in the United States and closed down all the consulates of those two nations.

Behind the scenes, Roosevelt volunteered another expeditionary force to relieve the British garrison in Iceland, an operation (Indigo) that was to be carried out on July 7. As agreed earlier in ABC-1, the U.S. Navy stepped up measures to provide escort of convoys on the leg between Canada and Iceland.

The Bismarck affair brought the U-boat war against shipping in the North Atlantic to a virtual standstill in the last ten days of May. The twenty boats in that area sank only two ships. Ottokar Paulshen in the new U-557, which nearly had been lost in an accident during its Baltic workup, got a 7,300-ton freighter; the Type IID duck U-147, commanded by Eberhard Wetjen, on an indoctrination patrol to the Atlantic, got a 2,500-ton freighter. When the new IXB U-109, commanded by Hans-Georg Fischer, age thirty-three, reached Lorient on May 29, having sunk only one ship on an eighteen-day patrol, Dönitz judged that Fischer was incapable of commanding a U-boat and sacked him. To replace Fischer, Dönitz brought back the Ritterkreuz holder Heinrich Bleichrodt, then commanding U-67, which was in the Baltic conducting sonar R&D work.

Altogether 347 loaded ships sailed from Halifax to the British Isles in SC Slow and HX Halifax convoys during May. The U-boats sank thirteen (or 4 percent) of these vessels—nine from convoy HX 126 and four stragglers from other eastbound convoys. In addition, U-boats in this area sank seven ships from the westbound convoy OB Outbound 318 plus six other ships that were sailing alone for 31,500 tons. The duck U-138 sank another lone freighter near North Channel. Total sinkings in the northern area in May 1941: thirty-one ships.

The successful attack on convoy HX Halifax 126 near 41 degrees west longitude, hastened the plans of the Admiralty and Western Approaches to deploy convoy-escort groups from Halifax out to 35 degrees west, where they were to hand over to the Iceland-based British escort groups. The first such Canadian escort group (of the Newfoundland Escort Force) sailed from St. John’s on June 2 to rendezvous with eastbound convoy HX Halifax 129. Commanded by J.S.D. (Chummy) Prentice, the group was composed of three Canadian corvettes, HMCS Chambly, HMCS Collingwood, and HMCS Orillia. Bedeviled by communications and engine problems, this pioneering Canadian force did not shine, according to the British, but all things considered, Prentice judged, his ships performed well, at least individually.

This convoy, Halifax HX 129, would be recorded as the first transatlantic eastbound convoy to be escorted “clear-across” or “end-to-end.” That is, a Canadian escort group from St. John’s to 35 degrees west; an Iceland-based British escort group from 35 degrees west to 20 degrees west; a British escort group from 20 degrees west to North Channel. Canadian and British aircraft in Newfoundland and Iceland provided limited air escort to the convoy but, as will be seen, due to diversion to help Bismarck in late May , no U-boats were available to attack HX 129. In a reverse procedure, convoy OB Outbound 331 was recorded as the first transatlantic westbound convoy to be escorted “end-to-end.” To field enough escort groups to provide this “end-to-end” transatlantic service, it was necessary to reduce the number of ships in each group, a calculated risk but one deemed worth running.



Thinly stretched in every theater, the Royal Navy was not prepared physically or mentally to fight U-boats in equatorial West African waters. Reginald (“Bob”) Whinney, a career officer who had specialized in ASW, was appalled by what he found when he arrived in Freetown to train the local escort force. The senior officer, Admiral Algernon Willis, Whinney wrote in his memoir,

was “severe, unbending, and very thin, ashen, unhappy-looking, possibly operationally tired, possibly not fit. What a choice where the crying need was for driving, but essentially benign, encouraging leadership.” Summing up the situation, Whinney continued:

“With few exceptions, the officers at Freetown were then the unhappiest collection I had ever met or was to meet in my whole Service career. There were several reasons for this. Certainly the climate was one of them. It was very debilitating due to the heat, the humidity and the prevalence of malaria. The living conditions were appalling; recreation was almost nil and social life did not exist. To cap this, it appeared that it was to Freetown, where the drink was duty-free—gin two pence a glass—that a number of officers who had been in recent trouble, including over drink, were sent. In many cases, these poor chaps had not enough to do. (Let it hastily be added that I was not in such a category.) Finally, Freetown was not an area of hot war and so got little priority from the Admiralty; and to cap the lot again, there was no inspiring lead from the top.”

By early May five large boats patrolled in South Atlantic waters. One, Oesten’s U-106, escorted the blockade-runner Lech from Brazil, a mission that took her to 50 degrees west longitude, the deepest penetration of the Western Hemisphere by any U-boat to then. At the insistence of the OKM (German Naval Staff in Berlin), U-106 remained in Brazilian waters to escort a second blockade runner, Windhuk, but the sailing of that ship was delayed indefinitely. When the OKM finally released U-106 on May 7, Oesten was low on fuel and had engine problems and had to rendezvous with the supply ship Egerland, which had been prepositioned in the South Atlantic to support Bismarck.

The other four boats patrolled off the African coast, resupplying from Egerland and another supply ship, Nordmark. Schewe in U-105 and Hessler in U-107 were the last boats to refuel from Nordmark. While they were doing so, on May 3 and 4, the new arrivals, Heinrich Liebe in U-38 and Viktor Schütze in U-103, patrolled off Freetown, picking off unescorted ships with little fear of ASW measures. Liebe sank two for 10,200 tons; Schütze sank six for 28,800 tons.

These four boats then switched places. After replenishing, Schewe’s U-105 and Hessler’s U-107 closed on Freetown, while Liebe’s U-38 and Schütze’s U-103 hauled off to mid-Atlantic to find Egerland. Schewe sank four ships for 28,400 tons, including the 11,800-ton British freighter Rodney Star; Hessler sank two ships for 16,300 tons. Counting past overclaims, Schewe’s victories earned a Ritterkreuz. While Schewe was sinking the fourth ship on May 16, a torpedo misfired and a crewman was seriously injured. On instructions from Dönitz, Schewe hauled out and transferred the injured man to Egerland, then refueled and set course for Lorient.

Three boats rendezvoused with Egerland from May 13 to May 17, then set off for Freetown waters to join Hessler in U-107. After they departed, on May 18, Egerland reported she had only six torpedoes left. Another Bismarck supply ship, Gedania, was therefore ordered to relieve Egerland. Two other boats sailed from Lorient for African waters in May: Eckermann’s U-A and Jost Metzler’s U-69, the first Type VII to attempt a very long-range cruise. U-69 then laid a minefield off Gold Coast on 23rd May. Here German Navy picked up first US Merchant Marine victim of the war.

Inbound to Africa to lay the mines, on the evening of May 21 the watch spotted a lighted southbound ship. The lights indicated she was a neutral, but Metzler believed she might be a disguised U-boat hunter. He cautiously approached her and asked for identification by signal light. When she replied “Robin Moor,” Metzler’s suspicions intensified because he could find no such ship in Lloyd’s Register. Moreover, when daylight came, Metzler saw the name Exmoor on her stern, listed in Lloyd’s as a 5,000-ton American ship. Was she Robin Moor, Exmoor, or a disguised hunter?

The captain of Robin Moor came across to U-69 in a whaler, bringing his ship’s papers and cargo manifest. He explained that the ship had only just been bought by Americans and that as a consequence, her name had been changed from Exmoor to Robin Moor. Metzler claimed he saw “radio apparatus” apparatus” and “guns” on the manifest and that the ship was therefore “a neutral carrying contraband” and thus fair game under the prize rules. Despite the explicit orders from Hitler, the OKM, and Dönitz to avoid any contact with American ships, Metzler decided to sink her. After the crew had abandoned ship in lifeboats, Metzler put her under with one torpedo and thirty rounds from his deck gun. Robin Moor was the first American ship to be sunk by a U-boat in the war.

When Dönitz heard the news of the Robin Moor sinking, he was furious. Metzler remembered that Dönitz sent “rocket after rocket to me, bombarding me with questions about the details and the reasons for the sinking.” No explanation seemed to satisfy Dönitz. London made a huge propaganda coup on Robin Moor affair espexially in US since Robin Mor was a US ship. “The Admiral’s tone conjured up a picture for me of a court-martial on my return,” Metzler wrote.


The hunting off Freetown , West Africa remained good.

• After refueling from Egerland, Heinrich Liebe in U-38 sank five ships for 29,400 tons, bringing his total to seven.

• Jost Metzler in U-69 bravely laid his TMB mines in the harbors of Takoradi on May 27, and Lagos on May 29. Later, Metzler lightheartedly described these extremely hazardous missions as “crazy exploits,” but they were successful. The British were forced to close both harbors. One mine damaged a 5,400-ton freighter in Takoradi; another sank a 2,900-ton freighter in Lagos.

• Viktor Schütze in U-103 sank four ships for 22,500 tons, including the 6,900-ton tanker British Grenadier, bringing his total to eleven.

• The Italian submarine Tazzoli sank the 8,800-ton Norwegian tanker Alfred Olsen.

• Homebound to Lorient, George Schewe in U-105 sank another ship, bringing his confirmed total to twelve for 70,500 tons.

• Jürgen Oesten in U-106, who had been sidetracked on escort missions for almost seven weeks, sank two ships for 13,200 tons, bringing his total to seven, plus the hit on the battleship Malaya.

• Günther Hessler in U-107 sank three more ships for 14,500 tons, bringing his total to eleven, including a second tanker, the 8,000-ton Dutch Marisa.

The aggregate sinkings of the boats in the South Atlantic in May were more than sufficiently impressive to justify the “diversion” of these boats from the North Atlantic. The sinkings served another purpose as well: They compelled the British to drastically curb the unescorted ship traffic in that area, to increase convoying from Freetown, and to draw a substantial number of surface escorts from the North Atlantic to the South Atlantic. Accordingly, Dönitz directed two more IXBs, U-66 and U-123, to sail to West Africa in June.


Thanks to the priceless intelligence haul from Lemp’s U-110, British codebreakers could read naval Enigma fluently and currently throughout the month of June. The torrent of information, which the British called Most Secret Ultra (shortened to Ultra), gave a select few in the Admiralty an astounding view of the Kriegsmarine’s innermost secrets, including everything about U-boat operations. Rodger Winn’s assistant in the U-boat Tracking Room, Patrick Beesly, remembered: “We rapidly learned the exact number of U-boats at sea, and not only the contents of their own signals but, even more important, the instructions constantly being pumped out to them by Dönitz from his headquarters in Lorient.”

The radio traffic between Dönitz and his skippers also revealed to the Admiralty day-by-day positions of nearly all the U-boats. Hence the Admiralty had an opportunity to organize task forces and “pounce” these boats by surface ship and aircraft and destroy them, putting an end to the U-boat menace in one simultaneous operation. But to attack twenty-odd U-boats in diverse locations simultaneously, the Admiralty believed, would tip off the Germans that Enigma had been broken and lead them to take corrective measures, such as changing the keys, or perhaps even introducing a new code machine.

Rather than attack the U-boats frontally, the Admiralty elected to impede their operations in indirect ways. These were principally two: by routing convoys away from the known U-boat positions and by thwarting the plan to use Bismarck’s supply ships for refueling U-boats at sea.

The refueling scheme was to be thwarted by directly confronting the supply ships and capturing or sinking them, as if the British had come upon them as a result of comprehensive and diligent blue-water patrolling. To be sure, there was a risk of arousing German suspicion, but less so in sinking big surface ships because the surface ships were easier to detect by radar than U-boats. The Admiralty knew, from breaking Enigma dispatches from Bismarck, that Lütjens had informed the OKM that British surface-ship radar was amazingly effective, capable of picking up a surface ship at a range of “at least 35,000 meters,” or about twenty miles.

Royal Navy assault on Bismarck’s supply ships began on June 3 in the North Atlantic. The cruisers HMS Aurora and HMS Kenya attacked the 10,000-ton German tanker Belchen, which was parked eighty miles southwest of Greenland. Belchen had refueled Kleinschmidt’s U-111 and Paulshen’s U-557, and when the cruisers struck, she was in the process of refueling Korth’s U-93. Belchen threw off the hoses and scuttled. Korth dived but he shied from attacking the cruisers while they destroyed Belchen with accurate gunfire.

Later that day, Korth surfaced and rescued all fifty survivors of Belchen. Dönitz instructed him to make for another Bismarck supply ship, Friedrich Breme, offload the survivors, refuel, and resume his patrol. But Korth demurred on the grounds that should that rendezvous fail, he did not have enough fuel to reach France. Halfway back to Lorient, on June 6, Korth spotted and reported a southbound convoy, but owing to his shortage of fuel and the presence on board of the fifty Belchen survivors, he did not attack or shadow it for the benefit of other boats. Although Korth had won his Ritterkreuz earlier on this patrol, when he arrived in Lorient, Dönitz upbraided him for not attacking and tracking the convoy, regardless of the presence of the Belchen survivors. Logging that Korth seemed to be losing his fighting edge, Dönitz decided to send him to West African waters on his next patrol.

The loss of Belchen was a stiff blow to Dönitz. She had been ideally situated to resupply the western patrol line, enabling those boats to double the time in the operating area. After Korth in After Korth in U-93, Walter Kell, age twenty-seven, commanding commanding the VIIC U-204 on his maiden patrol from Germany, had been next in line to refuel from Belchen. So that operation, and several others as well, had to be canceled.

In the two days following the destruction of Belchen, June 4 and 5, Royal Navy naval task forces struck at four other German supply ships in the North and South Atlantic simultenously thanks to intelligence guidence of ULTRA. Aircraft from HMS Victorious, the battleship HMS Nelson, and the cruiser HMS Neptune teamed up with the armed merchant ship Esperance Bay, forcing the 4,000-ton German supply ship Gonzenheim to scuttle. In the same area, the destroyer HMS Marsdale, trained for boarding, captured the 9,000-ton German tanker Gedania before she could scuttle. In southern waters, the light cruiser HMS London and the destroyer HMS Brilliant forced the 9,900-ton German tanker Esso Hamburg and the 9,800-ton German tanker Egerland to scuttle.

In the capture of Gedania, which was en route to relieve Egerland, the British Royal Marines who boarded her and Germans fought a pitched battle aboard tanker, during which several Gedania crewmen were killed. After the victory the British marines found numerous secret papers, including Enigma materials and the operational orders issued to Gedania. These orders contained a wealth of new information: instructions for conducting a rendezvous with a U-boat (coded meeting points, communications procedures, recognition signals), precise (coded) routes to be followed by supply ships and blockade runners when approaching French ports, and, not incidentally, the location of the North Atlantic weather-reporting trawler during June 1941.

Thanks to this information Submarine Tracking Room in OIC , Western Approaches Command and British Admiralty quickly went to work. First on 6th June 1941 , a 9.500 ton German blockade runner Elbe was intercepted by Swordfish and Fairey Blackburn aircraft from Royal Navy carrier HMS Eagle off Azores and forcing German blockade runner to scuttle when cornered.

Dönitz learned of the loss of Egerland from Heinrich Liebe in U-38, who was approaching her to replenish when she was scuttled and who then searched unsuccessfully for survivors. It was another blow. Her loss and the loss of her relief, Gedania, meant that the highly rewarding U-boat operations off the West African coast were to be interrupted until a substitute resupply ship could be stationed in those waters. Dönitz therefore directed the five boats remaining in the Freetown area to replenish, if necessary, from another Bismarck supply ship, the 10,700-ton tanker Lothringen, which had parked farther north.

Continuing their secret campaign, Royal Navy had five more successes. On June 12 the cruiser HMS Sheffield intercepted and forced the 10,400-ton German tanker Friedrich Breme to scuttle off Dakar. On June 15 the carrier HMS Eagle and the cruiser HMS Dunedin captured German tanker Lothringen intact , obtaining Enigma materials and wiping out the proposed resupply of the U-boats in the Freetown area. On June 21 light cruiser HMS London forced the 4,400-ton German supply ship Babitonga, (a merchant-raider supply ship), to scuttle. On June 23 destroyers of the 8th Flotilla and the destroyer HMS Marsdale teamed with aircraft and forced another German merchant-raider supply ship, the 3,000-ton Alstertor, to scuttle.

Nor was that all. Thanks to intelligenge captured on German tanker Gedania , on June 28 the cruiser HMS Nigeria and three destroyers of the Royal Navy Home Fleet pounced on the 136-foot, 344-ton German weather-reporting trawler Lauenburg, commanded by fifty-eight-year-old Hinrich Gewald off Greenland. A boarding party from the destroyer HMS Tartar, commanded by Lt. T. Hugh P. Wilson and advised by code-breaker Allon Bacon, captured the trawler and intelligence materials of “inestimable value” (as the Admiralty later put it), including the daily Enigma ring and plugboard keys for July 1941. These enabled Bletchley Park to continue reading naval Enigma fluently and currently through that month.

Denied the services of the supply ships Egerland, Gedania, and Lothringen, which, as related, the British wiped out, and badly in need of refits or overhauls and rest for the crews, one by one the boats in West African waters returned to France. George Schewe in U-105 and Jürgen Oesten in U-106 arrived on June 13 and June 18, having been out for 112 and 110 days, respectively. Dönitz had high praise for both skippers. Schewe’s score of twelve ships for 70,500 tons established a new record for a single patrol. Trailing U-105 homeward by about a week, Heinrich Liebe in U-38 sank his eighth ship, the 7,600-ton British freighter Kingston Hill. This sinking put Liebe over the 200,000-ton mark and he thus became the sixth skipper to earn Oak Leaves to his Ritterkreuz. Having commanded U-38 since the outbreak of war, Liebe had been in continuous Atlantic combat longer than any other skipper. When he reached Lorient, Dönitz sent him to a job in the Training Command, but the weary U-38 was retained in the Atlantic.