While the fighting in Norway was still in progress, on May 10 Hitler launched the long-postponed offensive against the West. The German blitzkrieg smashed through Belgium and northern France, splitting the Allied ground forces. The Chamberlain government fell; Winston Churchill moved up to the post of Prime Minister. Churchill attempted to reinforce and to rally the dispirited and defeatist French, but it was a lost cause. France was doomed.
Having been badly roughed up in Norway, the Kriegsmarine was not in shape to contribute much to the offensive in France. Owing to the loss of five oceangoing U-boats in the Norway operation and the need to refit the others and to give the combat-weary crews a rest, Dönitz deployed none during the early stages of the blitzkrieg. Submarine support was restricted to patrols by eight ducks in the North Sea. Three ducks sank six ships for 17,400 tons, including the French submarine Doris and the British destroyer Grafton, the latter while evacuating British troops at Dunkirk. The British sloop Weston trapped one duck, U-13, commanded by Max Schulte, age twenty-four, forced it to scuttle, and captured its crew.*
In truth, the U-boat arm had not much heart to resume the fight. “Faith in the torpedo had been completely lost,” Dönitz wrote. “I do not believe that ever in the history of war men have been sent against the enemy with such a useless weapon. These brave, enterprising [U-boat] crews, who had proved their worth during the previous months of the war, had been plunged into a state of dismal depression … a slough of despond.”
In the days immediately following Norway, Dönitz collected and meticulously analyzed the torpedo-firing data. The skippers had carried out a total of thirty-eight attacks: four against battleships, fourteen against cruisers, ten against destroyers, and ten against transports. Discounting marginal attacks from long range at highspeed targets in poor light or other unfavorable conditions, Dönitz concluded that had the torpedoes not failed, “certain hits” (and probably sinkings or severe damage) would have occurred in one of the attacks on the battleships, seven on the cruisers, seven on the destroyers, and five on the transports. In summary, he calculated that about twenty enemy warships and transports had escaped almost certain destruction because of torpedo failures.
Dönitz used this damning data to mobilize internal political pressures against the torpedo bureaucrats, and he won over Admiral Raeder and the OKM. Upon receipt of Dönitz’s “shattering summary,” the OKM diarist commented that the “continual failure of the torpedoes, resulting from catastrophic technical deficiencies, must be regarded as a calamity … a failure of historical significance in German naval warfare at a time which is of decisive importance….” Admiral Raeder declared that the correction of submarine torpedo defects was the Navy’s “most urgent problem” and hastened to assure Dönitz and his men that “the defects are known and being put right” with the highest possible priority.
Dönitz devoted a large share of his working hours to seeking a solution to the torpedo defects—but not happily. “It is monstrous,” he wrote in his log, “that I should have to be burdened with lengthy discussions and investigations of the causes of torpedo failures and their remedy. This is the business of the technical directorates and departments. But as long as these authorities are slow to do what is necessary, I am forced to take action myself.”
By this time Dönitz had lost all confidence in the magnetic pistol. It was too complicated and too sensitive. Furthermore, he (rightly) believed that the British had perfected a way of reducing the magnetic fields of their ships—probably by degaussing, he thought—rendering the magnetic pistol less effective. He therefore urged that highest priority be assigned to correcting the depth-keeping defect and other suspected defects in the impact pistol.
With the return of good weather to the Baltic, the “Torpedo Dictator,” Dr. Cornelius, had been carrying out intensive tests of the impact pistol. The results, presented about May 1, were “staggering” and “criminal,” as Dönitz put it in his diary. Cornelius reported “a high rate of failure” owing to a poor, overly complex, and “clumsy” design. The weakness had not been detected theretofore because the torpedo technicians had not tested the pistol adequately in peacetime.
A few days after Cornelius revealed these test results, on May 5, the Germans captured the British submarine Seal; a 1,500-ton minelayer. When the Germans towed Seal to Germany, it was found that she carried twelve torpedoes (six in the tubes, six reloads) fitted with contact pistols. After Dönitz and his staffers had closely examined the pistols, Dönitz declared them to be “very sound” and “efficient” and he insisted that they be “copied.” Cornelius concurred, and by this means the Germans were able to produce a reliable contact pistol in a very short time.
Meanwhile, Cornelius had some encouraging news. On May 11 he pronounced that the depth-keeping defect had been fixed. Torpedoes could be relied upon to run within a foot and a half of the depth setting. Furthermore, he asserted, “improved firing” of the magnetic pistol had been achieved.
The depth-keeping defect had not, in fact, been completely fixed. Nor would it be for another two years. There was another as-yet-undetected fault. The rudder shaft of the torpedo passed through the balance chamber, where the hydrostatic valve controlling the depth setting was located. The chamber was not airtight. As a result, when the boats ran submerged for prolonged periods (as in Norway) and the internal air pressure rose, the air pressure in the balance chamber likewise rose. This confused the hydrostatic valve, which was designed to operate at sea (or atmospheric) level, and caused it to set the torpedoes to run deeper. Since the latest testing had been carried out at sea level from surface craft or U-boats that had not remained submerged for very long, the leak in the balance chamber had no adverse effects on the hydrostatic valve, and so this flaw remained undetected.
Dönitz and his staff agonized over what to do: resume the U-boat war in the Atlantic or wait for improved torpedoes? His chief of staff, Eberhard Godt, Dönitz remembered, was of the “emphatic opinion” that the U-boat arm should not be committed to battle until all the torpedo defects had been eliminated. But Dönitz believed that any delay would do “incalculable harm” to the morale and efficiency of his men. Notwithstanding prematures and other failures, the Atlantic boats, employing magnetic pistols, had achieved considerable success in February. Dr. Cornelius had pronounced the depth-keeping defect fixed and some “improvement” in the magnetic pistol. As long as there was “even a slender prospect of success,” Dönitz believed, the U-boat war in the Atlantic should be resumed.
Before that could happen, the men had to be reassured and encouraged. Admiral Raeder did his part with cheer-up visits and by awarding a Ritterkreuz to Dönitz. Dönitz, in turn, secured a Ritterkreuz for Werner Hartmann, who had sunk nineteen ships to exceed the leading ace Herbert Schultze, and one for Otto Schuhart, who had sunk the carrier Courageous in the early days of the war.* Dönitz personally visited every flotilla staff and U-boat to exhort his men.
Dönitz also made some important command and staff changes. He relieved three skippers: Hundius Flotilla commander Werner Hartmann in U-37, Herbert Sohler in U-46, who had returned from Norway in a state of “nervous exhaustion,” and Herbert Schultze in U-48, who was ill and had to be hospitalized with a serious stomach or kidney disorder. Dönitz named Hartmann to be his first staff officer, replacing Viktor Oehrn, age thirty-two, who replaced Hartmann in U-37. He named Sohler commanding officer of the Wegener Flotilla, replacing Hans-Rudolf Rösing, who replaced Schultze in U-48. Prien’s able first watch officer, Engelbert Endrass, age twenty-nine, replaced Sohler in U-46.
In resuming the U-boat war in the Atlantic, Dönitz planned to replicate the opening assault of September 1939: a maximum commitment of force across the broadest possible front. But this plan was frustrated by Hitler and by the jam-up in the shipyards. The Führer insisted that the U-boat arm continue hauling supplies to the beleaguered German ground forces in Norway. In response, the OKM directed Dönitz to assign one-third of the oceangoing force (seven boats) to these supply missions. On appeal, Dönitz was able to reduce the supply missions to merely two (U-26, U-122), but the reconversion of the other five boats from supply back to attack configuration delayed their availability. The jam-up in the shipyards delayed the refits of other boats. As a consequence, Dönitz was compelled to postpone the opening blow—the maximum commitment of force—to June.
Six oceangoing boats sailed in May to reopen the Atlantic U-boat war. Infuriatingly, mechanical problems compelled two boats, U-28 (Kuhnke) and U-48 (Rösing), to abort while still in the North Sea. The other four, U-29 (Schuhart), U-37 (Oehrn), U-43 (Ambrosius), and the new VIIB U-101, commanded by Fritz Frauenheim, age twenty-eight, from the duck U-21, reached the Atlantic. To enhance their chances for success, Dönitz had obtained from Hitler another relaxation in the rules, which, in effect, permitted unrestricted submarine warfare in British and French waters. Commencing May 24, U-boats were allowed to sink without warning any ship, including unescorted neutrals and passenger ships.
Viktor Oehrn, new skipper of the famous U-37, led the way. Oehrn was very much aware that for internal political reasons and for rebuilding morale in the U-boat arm it was vital for U-37 to achieve a smashing success. He got off to a promising start, sinking a 5,000-ton Swede and severely damaging a 9,500-ton British freighter with his deck gun.
While in the Western Approaches on May 23, however, a calamity occurred. Oehrn fired five torpedoes—all with the improved magnetic pistols—and all five failed. Oehrn broke radio silence to report the failures: two prematures, two non-detonators, and one erratic runner.
Dönitz was dismayed and Furious. He immediately barred use of magnetic pistols and refused again to authorize their use until they had been fixed beyond any shadow of doubt. He ordered Oehrn and all other skippers to switch to impact pistols, which had recently been improved. At the same time, he demanded that work on copying the British impact pistol recovered from the captured Seal be carried forward with utmost urgency.
The switch to the improved impact pistols produced immediate returns for Oehrn. In the days following, he sank three ships by torpedo, including the 10,500-ton French freighter Brazza. He went on to sink another five ships and a trawler: one by demolition, four by gun, and one by a combination of gun and torpedo. His victims included the 7,400-ton British tanker Telena.
One of the sinkings was to become controversial: the 5,000-ton British freighter Sheaf Mead, sunk in the afternoon of May 27, off Cape Finisterre, with the loss of thirty-one men. Before shooting, Oehrn observed that the freighter was armed and painted warship gray: Several guns were on the stern and perhaps another concealed under a canvas structure amidships. Having been warned by Dönitz to expect armed British auxiliary cruisers in this area (off Vigo, Spain), Oehrn convinced himself that Sheaf Mead was one, and therefore, when he surfaced, he made no attempt to help the survivors. He logged:
A large heap of wreckage floats up. We approach it to identify the name. The crews have saved themselves on wreckage and capsized boats. We fish out a buoy. No name on it. I ask a man on the raft. He says, hardly turning his head, “Nix-name.” A young boy in the water calls, “Help, help, please.” The others are very composed; they look damp and somewhat tired and have a look of cold hatred on their faces. Then on to the old course.*
Having exhausted his torpedoes and ammo, Oehrn returned U-37 to Wilhelmshaven after a mere twenty-six days at sea. Dönitz was ecstatic. Oehrn had achieved the objective, reopening the Atlantic U-boat war with resounding successes. In all, Oehrn put down ten confirmed ships for 41,207 tons. This was a record first patrol in numbers of ships sunk and only 700 tons shy of Schuhart’s record 41,905 tons sunk in a single patrol.
The other three boats followed U-37 into the hunting area by about a week. Neither U-29 (Schuhart) nor U-43 (Ambrosius) had any luck. But Fritz Frauenheim, making his first Atlantic patrol in the VIIB U-101, sank three British freighters for 14,200 tons in the Western Approaches. Thereafter the boats patrolled Iberian waters where, if necessary, they could clandestinely refuel in Spanish ports.
Near Lisbon on June 6, Frauenheim in U-101 came upon a magnificent target, identified as a huge Greek passenger liner. Frauenheim surfaced, approached, and ordered the captain to abandon ship within ten minutes. The ship was not a Greek, but rather the 24,000-ton United States passenger liner Washington, bound from Lisbon to Galway, Ireland, jammed with American men, women, and children fleeing the war zone. On close inspection, Frauenheim discovered his error and shouted to the captain: “Sorry. Mistake. Proceed.” No harm was done, but what was perceived as a very close call caused a great public uproar. Berlin at first attempted to cover up, charging (à la Athenia) that the submarine was British, but finally conceded that the submarine was German and that it had stopped Washington in error.*