In support of Hitler’s planned attack on France in November 1939, Admiral Raeder and the OKM had ordered German surface ships, aircraft, and submarines to mine British seaports. The primary aim of the mining campaign was to shut off the flow of British troops and supplies to the continent. A secondary aim was to disrupt or shut down British merchant shipping, sowing terror and panic.
Restricted by a shortage of magnetic mines, which had not been mass-produced in peacetime, the campaign got off to a halting start. In October four ducks laid, or attempted to lay, minefields, each consisting of nine delayed-action TMB magnetic mines. Two fields were flops. That of Horst Wellner in U-16, off Dover, sank one small tugboat. Moreover, after laying the field, Wellner hit an Allied mine in the Dover-Cape Gris-Nez field on October 24, and U-16 was lost with all hands. That of Harald Jeppener-Haltenhoff in U-24, at Hartlepool, sank only one 1,000-ton coaster.* Two fields produced handsomely. That of Hans Meckel in U-19, off Hartlepool, sank three freighters for 12,344 tons. That of Fritz Frauenheim in U-21, courageously planted off the British naval base in the Firth of Forth, wrecked the new British heavy cruiser Belfast, a spectacular victory for the ducks.
The oceangoing boats were to foul British west coast ports, which were beyond reach of the ducks or German aircraft. Dönitz assigned these missions to the available Type VIIs of the Salzwedel Flotilla, which, pending modification, had been declared unsafe for torpedo patrols. The first, most important, and dangerous mission went to Paul Büchel in U-32, who had planted a (nonproductive) minefield in the Bristol Channel in September. Büchel’s destination was Loch Ewe, in northwest Scotland, where the Home Fleet based after Prien’s raid in Scapa Flow. But U-32 was not seaworthy and the U-31, commanded by Johannes Habekost, substituted.
Habekost crammed eighteen TMB mines into U-31. Off Loch Ewe he tangled the boat in a torpedo net—a harrowing episode—but he finally broke free, laid the mines in the outer channel, and returned home after ten days, the shortest patrol on record. The field produced no immediate results and was therefore believed to be a failure. But thirty-seven days later, on December 4, the Home Fleet flagship, the battleship Nelson, triggered one of the mines, incurring such heavy damage she had to be dry-docked for four months. The British concealed this disaster from the Germans.
The U-33, commanded by Hans-Wilhelm von Dresky, drew the next mission: Bristol Channel, where Büchel in U-32 had apparently mislaid his field in September. Since it had to be assumed that the British were aware of the submarine minelaying and therefore the boats could not sail utterly defenseless, von Dresky carried twelve TMB mines and six torpedoes. Outbound in the North Sea, a crewman remembered, both diesels broke down and U-33 had to lie on the bottom for three days while the engineers made repairs. “The boat was not really seaworthy,” the crewman explained. “The crew was very nervous. Many [men] were reluctant to go back to sea in this boat.” However, the field was highly productive: three big ships, for 25,600 tons sunk, including the British tanker Inverdargle, forcing the British to close Bristol for the second time.
After laying the field, von Dresky sought gun and torpedo targets. Off North Ireland he stopped five British trawlers and, after permitting the crews to abandon ship, he sank them all by gun. Homebound in the Orkneys, in miserable weather, he destroyed by gun and torpedo the 3,700-ton German freighter Borkum, which British warships had seized as a prize. Unwittingly, von Dresky’s gunfire killed four German crewmen. When the boat limped into Germany, Dönitz commended von Dresky for a “well-conducted” patrol, but U-33 had to be sent back to the shipyards for extensive repairs.
The mining campaign built up a full head of steam in November. Finally getting into action, German surface ships and aircraft, operating under cover of the long nights, assailed British east coast and channel ports. Dashing across the North Sea and back, the surface ships laid over 500 mines. In separate missions over three nights the Luftwaffe parachuted forty-one mines in the mouth of the Thames River, off the Humber, and at Harwich. One of the Luftwaffe mines was mis-dropped onto mudflats at Shoeburyness. The British recovered it intact, quickly learned the secrets of the magnetic mine, and initiated a crash R&D program to produce countermeasures.
The surface-ship mine offensive was highly effective. It forced the British to close down numerous east coast and channel ports and brought shipping to a standstill. The psychological impact was as great as—or greater than—the sinkings caused by the U-boats. Seeking to calm the shocked British population and to chastise Hitler for employing a sinister and barbaric weapon, the Chamberlain government immediately revealed the secrets of the magnetic mine (“An amazing new invention,” said one British official) but promised that “science and intelligence” would deal with it as effectively as it had dealt with the U-boat menace.
In the stepped-up offensive, seven ducks sailed to lay minefields in November. Two were flops: that of Otto Kretschmer’s U-23 off the British naval base in Cromarty Forth (Invergordon) and that of Herbert Kuppisch’s U-58 off Lowestoft. The other five, at Lowestoft, Ordfordness, Yarmouth, and Newcastle, produced six sinkings for 15,000 tons and damage to one freighter for 4,434 tons.
Three of these seven sinkings by the ducks were small ships of 209, 258, and 496 tons, which became known to the Germans. This revelation led Dönitz to question the reliability of the TMB magnetic mine with the same intensity he had questioned the reliability of the torpedoes. In response, the Mine Directorate conducted “live” tests of the TMB in the Baltic Sea. The results confirmed Dönitz’s suspicions. The mines, the Directorate conceded, were not “positively lethal” when laid on the bottom at ninety-eight feet (thirty meters) per instructions, but rather only at eighty-two feet (twenty-five meters). Moreover, the tests revealed, the pistols were overly sensitive. As a consequence, Dönitz directed the submarine crews to lay TMB mines sixteen feet shallower than designed and to “coarsen” (or desensitize) the magnetic pistols.
Dönitz had another complaint. He did not believe the 1,200-pound warhead of the TMB was sufficiently powerful for use against big, heavily armored capital ships. He requested a mine with twice the power of the TMB. In striking contrast to the torpedo technicians, the mine technicians responded willingly and enthusiastically. They quickly converted a big submarine floating mine, the TMA, then going into production, to a ground mine. Redesignated the TMC, it had a huge warhead of 2,200 pounds and was believed to be lethal up to a depth of 118 feet (36 meters).
Two Type VIIs of the Salzwedel Flotilla, which had been in the shipyards for weeks, drew Atlantic minelaying assignments in November. These were Günter Kuhnke’s U-28 and Otto Schuhart’s U-29. Both loaded twelve TMB mines and six torpedoes to continue the campaign in the Bristol Channel.
En route to Bristol, Kuhnke sank two ships with torpedoes. The first was the 5,000-ton Dutch tanker Sliedrecht, fair game under the newly relaxed rules regarding neutral tankers. After the crew abandoned ship, Kuhnke fired a single torpedo, which demolished the ship in a “terrific flash.” He left the survivors to fend for themselves and only five lived. The second kill was the 5,100-ton British freighter Royston Grange, sunk in the Western Approaches after the crew had abandoned ship.
Kuhnke laid his field at Swansea and returned to Germany. Since it produced no immediate results, it too was believed to be a failure. The U-28 went back into the shipyards for more weeks of repairs and modifications. About sixty days later one of the mines triggered and sank an important ship: the 9,600-ton British freighter Protesilaus.
The hero Otto Schuhart in U-29, who had sunk the carrier Courageous, was directed to lay his field at Milford Haven. But he broke radio silence to say that foul weather and a bright moon had forced him to abort the mission. Dönitz directed Schuhart to attempt an alternate location, but apparently Schuhart’s heart was not in the task and he returned to Germany with a full load of twelve mines and six torpedoes. Furious at the failure, Dönitz criticized Schuhart for being “too cautious,” but in view of Schuhart’s outstanding first patrol, Dönitz decided he would give Schuhart a second chance. The opportunity for redemption did not come soon; U-29 also went back to the shipyard for more weeks of modifications.
Five ducks laid or attempted to lay minefields in December. All five fields bore fruit, sinking a total of eight small ships for 13,200 tons. The field of Karl-Heinrich Jenisch in U-22, laid at Newcastle, was the most productive: four small freighters for 4,978 tons. Jürgen Oesten attempted to lay a second field in the dangerous waters of the Firth of Forth, but ASW forces drove him off before he could finish. The mines he planted bagged one small coaster. The largest ship, a 4,373-ton freighter, was sunk by the mines of Georg Schewe’s U-60, at Lowestoft.
Two Type VIIs mounted the Atlantic minelaying campaign in December: Lemp’s U-30 and Büchel’s U-32. Lemp was to plant a dozen TMBs in Liverpool, closing that important port. Büchel was to lay eight of the new, powerful TMC mines off the British naval base in the dangerous waters of the Firth of Clyde, where it was hoped the TMCs would bag a capital ship.
Lemp’s U-30 had been in the shipyards for seventy days undergoing battle-damage repair and modification. He believed the boat to be seaworthy, but while outbound near the Shetlands an engine failed and he had to return to Germany. He resailed, finally, on December 23, four days behind Sohler’s U-46, which was outbound to the Atlantic for torpedo patrol. Reapproaching the Shetlands on Christmas Eve, Lemp received a message from Raeder addressed to “all U-boats” at sea: “A Merry Christmas. Good wishes for successful operations.” Since all the ducks and the other oceangoing boats were in port, the greeting applied only to Lemp and Sohler.
Rounding the British Isles, Lemp reached the Butt of Lewis on the north end of the Hebrides in the early morning of December 28. There he came upon a British trawler. Believing his crew needed sharpening, Lemp battle-surfaced. After the British abandoned the trawler, he sank her with his deck gun. As it happened, that very day the 2,500-ton British freighter Stanholme hit one of the mines von Dresky had planted earlier in the Bristol Channel. London indignantly claimed Stanholme had been torpedoed without warning by a U-boat. Hearing the news in Berlin, the OKM wrongly attributed the sinking to Lemp. Perhaps mindful of the furor Lemp had caused by sinking Athenia, the OKM virtuously chastised Lemp for providing the British with an opportunity to condemn Germans for waging submarine warfare “during Christmas.”
To reinforce the depleted Home Fleet, the Admiralty had brought home two old (1915-1916) battleships: Warspite (which had been modernized in the late 1930s) and Barham. In addition, the old battle cruiser Repulse and the carrier Furious had arrived from Canada on convoy duty. Late in the afternoon of this same day—December 28—the Barham and Repulse, escorted by five destroyers, cruised off the Butt of Lewis, to backstop the cruisers of the Northern Patrol in case Gneisenau and Scharnhorst came out again.
Resuming his voyage south, Lemp sighted the top hampers of Repulse and Barham late that afternoon. He submerged on a closing course and coolly made ready the four electric torpedoes (with magnetic pistols) in his bow tubes. Boldly maneuvering under the destroyer screen, Lemp fired two torpedoes each at Barham and Repulse. Lemp and his men heard one of the four torpedoes hit Barham, and cheered. It struck forward, causing considerable damage and flooding in the ammunition lockers. The other three torpedoes malfunctioned or missed.
In the excitement and confusion that ensued, the British botched the submarine hunt and Lemp withdrew without undergoing counterattack. That night he galvanized Dönitz and Berlin with this message: “Attacked two Repulse class, escorted by destroyers … one hit probable.” B-dienst intercepted and decoded Barham’s damage report and the instructions to her from the Admiralty to put into Liverpool for repairs because the Firth of Clyde was too crowded. Repaired in a Liverpool shipyard, Barham was out of action for, three months.
Liverpool was also Lemp’s destination. Approaching with utmost caution, he arrived there and laid his twelve TMB mines. This well-planted field paid off handsomely. Within the next thirty days one tanker and three big British freighters for 22,472 tons blew up and sank, and a 5,600-ton freighter, Gracia, was severely damaged. As a result, the British were compelled to close Liverpool.
Dönitz had high praise for Lemp. The minelaying, Dönitz commented in his diary, was well carried out and required “a lot of dash, thought, ability and determination.” If Lemp had been under a cloud for sinking Athenia, his hit on Barham and the Liverpool minefield removed it. Including Athenia and the victims of his mines, Lemp’s confirmed sinkings totaled eight ships for 45,678 tons, ranking him first in the Salzwedel Flotilla and third in the entire U-boat arm in tonnage sunk after Herbert Schultze and Günther Prien.
Büchel in U-32 finally sailed in late December after eighty-nine days in and out of the shipyards. Rounding the British Isles, like Lemp he paused to sink a ship (a 1,000-ton Norwegian) to sharpen the crew. Continuing southward, he entered North Channel and proceeded with due caution to the Firth of Clyde, which was heavily patrolled and protected by antitorpedo nets. Daunted by the intense ASW measures, Büchel balked at planting the mines in midchannel where Dönitz had specified, and dropped them in a less promising location in deeper water. When Büchel returned to Germany, Dönitz sacked him, angrily noting in his diary that the job had been “too difficult for this commanding officer.” None of the TMCs exploded. Thus the first use of this extremely powerful weapon failed.
The ducks and oceangoing boats mounted a total of twenty-two minelaying missions in British home waters between October and December, 1939, planting 218 mines. One oceangoing boat (U-29) with twelve mines aborted at Bristol; one duck (U-61) was driven off before it finished laying its field in the Firth of Forth. Several fields were mislaid, most notably U-32’s TMCs in the Firth of Clyde. Two duck fields, probably mislaid, produced no sinkings; two others sank but two very small ships. The five minefields (sixty-two mines) sown by oceangoing boats sank ten ships for about 58,000 tons; the sixteen minefields (about 140 mines) sown by the ducks sank twenty ships for 46,400 tons. The combined campaigns produced thirty ships sunk* for 104,400 tons, a statistical average of 1.4 ships per boat per patrol and one ship of 3,500 tons sunk for every seven mines planted. One duck, U-16, had been lost on a mine mission.
The Admiralty estimated that during the period October-December, 1939, seventy-one merchant ships were lost to enemy mines in British waters. The mines planted by U-boat accounted for almost one-half (42 percent) of these losses, plus the severe damage to the cruiser Belfast and moderate damage to the battleship Nelson. Even so, Dönitz did not share the enthusiasm of Raeder and the OKM for submarine minelaying. It was tedious, time-consuming, and very dangerous. The observed or known returns per minefield appeared to be quite meager. He distrusted the TMB mines. Minelaying diverted a great many duck skippers from torpedo shooting which, in view of the greatly relaxed U-boat rules, offered many more opportunities for success as well as valuable combat training. German aircraft and surface ships could mine almost all the ports the ducks could reach.
Dönitz urged Raeder and the OKM to release submarines from minelaying, but he won only a partial victory. All further duck minelaying was suspended, except for two missions to Cromarty Forth. However, the Atlantic boats were to continue the campaign against ports on the west coast of Britain.