Hitler seized upon the Anglo-French guarantees to Poland as a pretext for abrogating the Anglo-German Naval Treaty. He did so publicly, in a sarcastic speech to the Reichstag on April 28 1939. Soon thereafter the Kriegsmarine laid the keels for the two super-battleships, Bismarck and Tirpitz. Despite these provocations and the public indignation and the stepped-up military preparations in Great Britain, Hitler continued to assert to his Nazi cohorts that neither Great Britain nor France would fight for Poland. Believing Hitler would pull another political rabbit out of his hat, Raeder naively—and irresponsibly—assured the Kriegsmarine that there would be no war with Great Britain.
Karl Dönitz was more convinced than ever that the opposite was the case. He believed that the “high state of tension” which Hitler had created between Great Britain and Germany could explode “into actual hostilities at any moment.” He therefore pleaded with Raeder and the OKM to approve a rapid increase in U-boat orders, with a major emphasis on Type VIIs, and to authorize theretofore prohibited U-boat exercises in the Atlantic Ocean. He got nowhere with his pleas for an increase in U-boat orders—the available shipyards were already jammed—but Raeder did permit the Atlantic exercises.
These exercises culminated in May 1939 with group or “wolf pack” attacks against a simulated convoy, composed of some Kriegsmarine vessels assigned to the annual fleet cruise to Lisbon and the western Mediterranean. A total of fifteen VIIs and IXs from the Salzwedel, Wegener, and Hundius flotillas participated. The “convoy” consisted of four German surface ships: a tanker, a freighter, Dönitz’s “command ship,” Erwin Wassner, and the Flotilla Salzwedel tender, Saar—the latter two vessels alternating as targets and defending escorts.
The fifteen U-boats deployed in five packs of three boats along a patrol line several hundred miles long. One pack quickly “found” the “convoy” and radioed a contact report to the other boats. In spite of clever evasive and defensive measures by the convoy—and extremely foul weather—the other boats converged on the target and attacked it relentlessly for over forty-eight hours, May 12 to 14. At the end of the exercise, thirteen of the fifteen boats converged for the final “kill.”
The exercise was wholly artificial and weighted to favor the U-boats. There were serious lapses in communications and tracking and gross errors in position reporting. Nonetheless, Dönitz could not have been more pleased. In a lengthy after-action critique, he concluded that the “principle of fighting a convoy of several steamers with several U-boats” was “correct” and that “the convoy would have been destroyed.” His group or “wolf pack” concept was therefore a sound one for defeating Great Britain; he renewed his pleas to Raeder for a step-up in the construction of Type VIIs.
Absorbed in the grandiose Z Plan, the OKM emphatically disagreed with Dönitz. The senior submarine planner at the OKM, Werner Fürbringer, a rear admiral and an assistant to Raeder’s chief of staff, Otto Schniewind, framed the response. “At the present moment,” Fürbringer wrote, “U-boat blockade of England has very little prospect of success for Germany. Any contradictory opinion, which takes comfort in the large number of our U-boats or in the idea that the English U-boat defense will not be effective far out in the Atlantic, can be dismissed as misleading” and, furthermore, it would be “irresponsible to commit the valuable U-boat crews” to such a war. “It can be taken as proven,” Fürbringer went on, “that every English convoy, no matter whether it operates along the coast or on the high seas, will be secured by defensive forces, fully capable of destroying with certainty any attacking U-boat, even under the surface.” In support of has argument, Fürbringer stressed the effectiveness of British sonar and predicted that the British would again resort to defensive minefields, which had been so deadly effective against U-boats in World War I. Until U-boats could be made “sonar-immune,” it was pointless to even consider starting a U-boat campaign against British commerce.
The Fürbringer paper dismayed and enraged Dönitz. In response he drafted a reply for Fürbringer’s superior, Otto Schniewind, vigorously rebutting Fürbringer’s arguments point by point. Going a step beyond—a large and career-risking step—he communicated his arguments directly and emphatically to Raeder, and asked that Raeder in turn place his views “before Hitler.” Hitler’s response, relayed to Dönitz through Raeder, was, as Dönitz remembered it, that “he would ensure that in no circumstances would war with Great Britain come about. For that would mean finis Germaniae. The officers of the U-boat arm had no cause to worry.”
THE FIRST WOLF PACK
By the time Dönitz was ready to launch the second wave of U-boats to the Atlantic in early October, the Allies had organized most merchant shipping into convoys. Composed of thirty to forty ships, the majority of the convoys arrived and departed the British Isles through the Western Approaches. The heaviest convoy traffic ran across the North Atlantic between the British Isles and the strategically situated British colony of Newfoundland and its neighbor, the Canadian maritime province of Nova Scotia.
By October 1939, the North Atlantic convoy system was fully in place. On the western end, the port of Halifax, Nova Scotia, was the gathering place. All ships bound for the British Isles that cruised between 9 and 15 knots had to join convoys. There were two types of convoys: Halifax Fast (designated HX-F), composed of ships that cruised at 12 to 15 knots; and Halifax Slow (HX), composed of ships that cruised at 9 to 12 knots. Ships that cruised at speeds over 15 knots (considered too fast to be vulnerable to U-boats) were allowed to proceed alone, as were ships that cruised at less than 9 knots (considered too slow and not valuable enough to warrant the holdup of faster ships).
On the eastern end, the British Isles, departing convoys were categorized as Outbound. Those convoys bound for Halifax or elsewhere in the western hemisphere (the reverse of the Halifax convoys), composed mostly of ships in ballast, were designated Outbound B or OB. Some ships in OB convoys peeled away after some days of travel and went due south down the mid-Atlantic to ports in West Africa. Ships outbound from the British Isles that cruised faster than 15 knots or slower than 9 knots were also exempt from convoys.* Most North Atlantic convoys were escorted only during part of the voyage. The inexperienced and small Royal Canadian Navy (six destroyers) and the Royal Canadian Air Force (RCAF) provided escort on the western end, going east several hundred miles with eastbound convoys and returning with westbound convoys. British and French surface ships and aircraft provided escort on the eastern end for Outbound convoys in a similar manner for a like distance. The important Halifax Fast convoys were escorted all the way across to the British Isles by Royal Navy capital ships (battleships, carriers) and their destroyer screens, or by cruisers. But only reluctantly. The long transatlantic voyage was very hard on these warships. The old destroyers assigned to this task (V and W class) could not cross the Atlantic without refueling, and the Royal Navy had not fully mastered ocean refueling. The modern destroyers could just barely make it across in heavy weather, which was the usual condition. Convoy escort was “defensive,” tedious, and boring for sailors trained to attack big German ships in complex fleet actions.
The Germans possessed a fairly accurate picture of Allied maritime traffic. During the 1935 crisis in the Mediterranean, when Italy invaded Abyssinia (Ethiopia), the Kriegsmarine codebreaking unit B-dienst (later directed by Heinz Bonatz) had broken the Royal Navy’s old-fashioned (nonmachine) operational codes and, later, the nonsecure British merchant marine code. From the outset of the war, B-dienst codebreakers had supplied the OKM with current information on the movements of most British capital ships and other naval formations as well as convoy routing and rendezvous points for the convoy escorts.
In the initial U-boat offensive the OKM had deployed the Atlantic boats to individual patrol zones before the convoys had formed. Almost all of the merchant ships they sank had been sailing alone. Now that convoying was in full swing, Dönitz believed the time was ripe to initiate his group (or “wolf pack”) tactics. The packs were to capitalize on convoy information provided by the codebreakers in B-dienst.
Dönitz planned to deploy two packs in October, composed of the ten boats he had recalled earlier: five Type VIIBs of the Wegener Flotilla and five Type IXs of the Hundius Flotilla. But that plan went awry. Five of the ten boats were unavailable: U-47 (assigned to the Scapa Flow mission) and U-52 (undergoing major repairs), U-38 (assigned to a special mission to Murmansk), U-39 (lost), and U-41 (undergoing major repairs).
The upshot was that Dönitz could mount only one pack, composed of six boats of an unwieldy mixture of types, from two different flotillas, which had not before exercised as a group: three VIIBs, U-45, U-47, U-48, and three IXs, U-37, U-40, and the U-42, the latter brand-new and rushed into service before completing a full workup. The senior officer, Hundius Flotilla commander Werner Hartmann, age thirty-seven, who had taken command of U-37, was to tactically direct the pack at sea.
Five of the six boats sailed independently into stormy, cold North Sea weather in the first week of October, going northabout the British Isles. Wrongly believing the Allies had not yet mined the English Channel, Dönitz ordered the last boat, U-40, a Type IX making its second patrol, with a new skipper, Wolfgang Barten, age thirty, to go by way of the channel to save time and catch up with the others.
While these boats were en route to the Atlantic, Hitler, poised to attack France (or so he thought), removed another important restriction on the U-boats. Commencing October 4, U-boats were permitted to sink on sight and without warning any blacked-out ship (including a neutral ship) sailing close to the British Isles in the Atlantic or North Sea and the French Atlantic coast. Dönitz and his skippers cheered this news, but to minimize charges of barbarism and inhumanity, Hitler had added a caveat: U-boats were still required to “save the crew” of any ship they sank if that could be done “without endangering” the U-boat.
Rushing to catch up with the other boats, U-40 ran at full speed through the English Channel on the surface. In the early hours of October 13, she hit a mine in the Dover-Cape Gris-Nez field. The boat blew up and sank immediately in 115 feet of water. Presumably, all hands on the bridge and in the forward compartments were killed instantly. But the watertight door in the stern room had been closed and as a result, nine enlisted men in that compartment survived the explosion and sinking. When they recovered from shock and ascertained what had occurred, the senior man, Otto Winkler, age twenty-one, organized an escape through the after deck hatch, which had a skirt for that purpose. After eating some biscuits, the men strapped on oxygen apparatus and flooded the compartment. When the water pressure in the compartment equalized with outside sea pressure, the hatch opened freely and the nine men—the first to escape a sunken U-boat—ascended.
Winkler was the last to leave the compartment. When he reached the surface he saw the eight other men swimming around in a cluster. It was dark—a new moon—and the channel water was frigid. Winkler thought he saw a lighthouse and began swimming toward it. Along the way he became nauseous and then he passed out. The next morning, two British destroyers (Brazen and Boreas) fished Winkler and two other survivors and five bodies from the water. All were wearing escape apparatus, labeled “U-40.” No trace was ever found of the remaining forty-six crew. Rushed to a hospital, Winkler and the other two lived to become prisoners. The next day, October 14, Boreas found an emergency telephone-equipped buoy, which had torn loose from U-40 in the explosion. Inscribed on a brass plate were these instructions: “U-boat 40 is sunk here. Do not raise buoy. Telegraph the situation to the nearest German naval command.”
Unaware of this loss, the other five boats of the “pack” headed for the Western Approaches one by one. First to arrive was the new, undertrained Type IX, U-42, commanded by Rolf Dau, age thirty-three. On the same day U-40 was lost, Dau found a 5,000-ton British freighter, Stonepool, which had separated from a convoy. Husbanding his torpedoes for pack operations, Dau attacked Stonepool with his 4.1” deck gun, but the freighter was armed, shot back, and radioed the SSS alarm. Two British destroyers, Imogen and Ilex, responding to the alarm, rushed up and attacked U-42 with guns, driving the boat under.
Attempting to evade, Dau took U-42 to 361 feet. But the destroyers fixed the boat on sonar and delivered an accurate and brutal depth-charge attack. One charge that exploded close over U-42’s stern ruptured the after-ballast tanks and lifted the bow to a 45-degree angle. In a desperate attempt to avoid sliding to crush depth stern first, Dau blew all ballast tanks. The U-42 shot to the surface like a giant cork, into the waiting arms of the destroyers, which instantly opened fire, scoring hits in the bow room. Holed fore and aft, U-42 began to sink. Ilex ran in at full speed to ram, but seeing that U-42 was doomed and sinking, she backed full astern to avoid damage to herself, and merely grazed the boat abaft the conning tower. Dau and sixteen men got out of the sinking boat through the conning tower hatch; the other thirty-two men were lost. Imogen fished the dazed German survivors from the sea.
By that time Dönitz had good information from the codebreakers of B-dienst on a special French-British convoy, KJF 3, inbound directly from Kingston, Jamaica, escorted by the monster French submarine Surcouf (two 8” deck guns). Assuming all six boats had reached positions in the Western Approaches, Dönitz ordered Hartmann to lead the pack in the attack. But two of the six boats had been lost and Hartmann, having sunk two neutral ships (a Swede and a Greek) en route, was behind schedule and too far away to take tactical command of the other boats.
Two VIIBs of the pack, operating independently, found the convoy and attacked. Herbert Schultze in U-48 sank two French ships from the convoy: the 14,000-ton tanker Emile-Miguet and the 7,000-ton freighter Louisiane, plus two British freighters, apparently stragglers from other convoys. Alexander Gelhaar in U-45 also sank two ships from the convoy: the 9,200-ton British freighter Lochavon and a prohibited vessel, the 10,000-ton French passenger liner Bretagne, which was running blacked out and therefore inviting trouble. While she slowly sank, British ships rescued 300 passengers.
Gelhaar in U-45 did not have to answer for this mistake. While he was pursuing another ship of the now-dispersing convoy, four British destroyers, Icarus, Inglefield, Intrepid, and Ivanhoe, which had responded to the SSS alarms, found U-45 and attacked. Nothing more was ever heard from U-45. She was the first VIIB and the first Atlantic boat to disappear without survivors.
The other two boats of the pack, U-37 and U-46, arrived too late to engage in a coordinated attack. However, on the morning of October 15, Hartmann in U-37 lucked into a straggler of the convoy, the 5,200-ton French freighter Vermont, and sank her with demolitions. But Herbert Sohler in U-46 never found the convoy at all. His sole contribution to the action was the interception of U-45’s last radio transmission (not received in Germany), which helped sort out Gelhaar’s first—and last—sinkings.
After the convoy dispersed, Dönitz, who was following the action by radio and by reports of distress calls and British movements provided by B-dienst, ordered the six boats (or so he thought) to move south to attack another convoy, HG 3, inbound from Gibraltar to the British Isles and to report results to date. Schultze in U-48 radioed four ships sunk for 29,000 tons; Hartmann in U-37, three ships sunk for 11,000 tons; Sohler in U-46, none. Wrongly believing Schultze and Hartmann had sunk a total of seven ships from the Caribbean convoy, Dönitz added all those to Gelhaar’s two and concluded that the first pack to attack an Allied convoy had sunk nine ships, an outstanding “success” that absolutely validated his pack doctrine. In reality, the first pack was so far a disaster: three of its six U-boats sunk; only four ships of the Caribbean convoy positively sunk, one of them a prohibited passenger liner!
While the boats were southbound on October 17, Hitler, still poised to attack France (as he thought), authorized a further relaxation in the rules. Henceforth U-boats could attack any “enemy” merchant ship (i.e., British or French) except big passenger liners, anywhere, without observance of the Submarine Protocol. In other words, U-boats were excused or exempted from the requirement to insure the safety of merchant-ship crews. This important relaxation allowed U-boats to wage unrestricted submarine warfare on all British and French shipping, except big passenger liners.
The luckless Sohler in U-46 was first to find convoy Homebound Gibraltar 3, which was heavily escorted by British destroyers transferring from the Mediterranean to home waters. He tracked the ships through the night, radioed a contact report, then submerged for a daylight attack. One of his first electric torpedoes pre-matured. In all, Sohler experienced seven torpedo malfunctions, but even so, he sank the 7,200-ton British freighter City of Mandalay. Brought into contact by Sohler’s report, Hartmann in U-37 sank the 10,000-ton British freighter Yorkshire and Schultze in U-48 got his fifth ship in as many days, the 7,250-ton British freighter Clan Chisholm.
Following this attack, Sohler broke radio silence to report the premature torpedo detonation and other torpedo problems. Shocked—and angry—Dönitz declared that the magnetic pistol was “not safe” under any circumstances and without consulting the OKM or the Torpedo Directorate, he ordered all boats to use only contact (or impact) pistols. Hence the more powerful effect of the magnetic pistol—exploding the torpedo beneath the ship—was lost. “We’re back to where we were in 1914-1918,” Dönitz noted bitterly in his war diary.
Upon learning that Dönitz had prohibited any and all use of the magnetic pistol, two days later, October 20, the Torpedo Directorate confessed to another defect. The torpedoes were indeed running deeper than set—6½ feet deeper. The Directorate technicians had known this all along, but did not report it to Dönitz because they did not believe it made that much difference when using magnetic pistols. But it did make a difference when using contact pistols. Dönitz hastened to relay this new discovery to his skippers, advising them to deduct 6½ feet from the usual depth settings for impact firing. The order introduced yet another complication. Since a depth setting of less than 13 feet was impractical when shooting in heavy seas, skippers were not to fire at any targets drawing less than 13 feet, such as destroyers.
Operations of the first wolf pack were terminated after the attack on the Gibraltar convoy. The two surviving VIIBs, U-46 and U-48, low on fuel and low on, or out of, torpedoes, returned to Germany, Herbert Schultze to rave reviews. In two patrols Schultze had sunk eight ships for 52,000 tons, elevating him to first place in total tonnage sunk. Extending his patrol to the approaches of Gibraltar, Hartmann in U-37 sank three more ships by gun and torpedo, establishing a new sinking record for a single patrol: eight ships sunk for 35,300 tons.
A careful after-action analysis of the first wolf pack deflated the earlier euphoria. In reality the attack on the Caribbean convoy was an uncoordinated free-for-all. Thanks to Sohler’s contact report, the attack on the Gibraltar convoy was slightly better coordinated. However, the boats had sunk only four ships from the Caribbean convoy and three from the Gibraltar convoy. Half the pack (three of six boats) had been lost to the enemy, two boats to convoy escorts. In a significant and far-reaching report, Hartmann, who had sunk only one ship from each convoy and who had found it impossible to “tactically coordinate” the other boats of the pack, recommended that the concept of flotillas and “local pack control” (at sea) be abandoned, and that all boats should be controlled individually from Dönitz’s headquarters.
Dönitz had three reasons for the failure to destroy the Caribbean convoy. First, the attack had been mounted too late—after the convoy was well into the Western Approaches and had been reinforced by local ASW vessels and had only a relatively short run to reach the safety of land. Second, in the confusion of combat, the boats making contact, U-45 and U-48, had not been able to transmit accurate data on the position, course, and speed of the convoy; hence help from U-46 had been lost. Third, there were too few boats in the initial attack—only two, actually—hence the escorts were able to concentrate on those two, sinking one, U-45.
The analysis led to three conclusions. First, convoys inbound to the British Isles from any direction had to be attacked as far out as possible in order to give the boats sufficient sea room for repeated attacks over several days and before the enemy added local ASW measures. Second, the boat first making contact with a convoy should not immediately attack, but instead should “shadow” it, transmitting “beacon” signals to “home” in other boats of the pack. Third, after the other boats arrived, all were to attack simultaneously in a single massive blow, which would scatter the convoy and overwhelm the escorts, maximizing opportunities for repeated attacks and minimizing counterattacks.
These tactics could be tested in Baltic training exercises, but not in Atlantic combat. There were not to be enough oceangoing boats to mount another full-scale wolf pack for months to come.