The German army had launched its large-scale counter-attack through the Ardennes against the Anglo-American forces on 16 December, and the U-boats were ordered to redouble their efforts to coincide with the assault. There had indeed been an increase in the number of U-boats at sea and sinkings achieved, see earlier. The Ardennes offensive had stalled by the end of the year, and the German army would be pushed back to its starting lines by mid January. Nevertheless, Hitler’s HQ staff estimated that stockpiled war supplies for the Allied armies in western Europe must now have run out, and further supplies would have to be brought by sea, highlighting the role of the German U-boats in aiding the land war. The New Year appeared to hold much promise for the U-boats conducting the Inshore Campaign, and U-boat Command wrote an optimistic appraisal of prospects for the coming year, attached in the form of several appendices to the end of their war diary for 15 January. However, not mentioned in this document, there remained substantial worries for the future.
Firstly, the Inshore Campaign had never been intended to be anything other than a stop-gap measure, necessitated by the fact that the older U-boats had been driven out of their Biscay bases, and that their intended replacements, the long-range Type XXI ‘electric’ U-boats, had been repeatedly held up by unexpected flaws in design and by Allied bombing raids. It was quite evident that concentrating nearly all the available U-boat force within the confines of British coastal waters would enable equally the Allies to relax convoy restrictions elsewhere and to concentrate enormous anti-submarine measures around the British Isles. Indeed, there was already evidence reported by the few very long-range Type IXD2 boats moving through the south Atlantic that this relaxation had already occurred.
It was apparent to U-boat Command that to push too many U-boats into confined areas around the British Isles would do little to improve sinkings of enemy ships, while any Allied escort group making a sweep could hardly fail to find targets. This concern was explicitly stated by Doenitz to Hitler, in one of their regular conferences which took place on 1 March. Hitler was advised that heavier losses of U-boats had to be expected, and that only the introduction of the Type XXI fast long-range U-boats could disperse the enemy defences. Doenitz himself, centred for several months in Berlin and immersed in the many problems incurred by the Navy as a whole as Germany’s military situation deteriorated, now rarely took an active role in U-boat operations. Admiral Godt, Doenitz’s deputy, and Kpt zS Roesing directed the Atlantic war.
Secondly, as the crews acquired confidence in operation of the new types of schnorchel, they became increasingly reluctant to surface, even when they could safely do so as in the case of some U-boats heading out for patrols in mid ocean or around Canada. One of the inshore boats, U 480, had been forced to surface after a very long submerged cruise as a result of a schnorchel malfunction. The commander later reported that the whole boat shimmered with phosphorescence and the entire heavy flak armament, for defence against incoming bombers, was corroded through and useless. He chose to dive again at the earliest opportunity, and did not feel inclined to resurface. However, U-boats were required to surface to transmit radio signals, although they could receive such signals while submerged, so that few signals were being sent to U-boat Command. Electrical and corrosive problems had also been reported due to the dampness of the boat when continually submerged. A side effect of the continued submergence was the difficulty of navigation, which tended to rely on sightings of prominent shore features. On 12 January, in Experience Order 212, U-boat Command reminded U-boats that ‘Navigation in coastal waters is a matter of life and death’ and must be done properly and not casually.
The submerged boats navigated by dead reckoning, radio-navigational fixes from ‘Elektra-Sonne’, whose bearings from transmitters in several Axis countries (including Spain) gave the boat’s position, use of the echo-sounder to determine the sea depth (marked on charts) and periscope bearings on lights or land. In this respect, the lights blazing from neutral Eire were of considerable value. At the end of January U-boat Command could advise that one U-boat had navigated solely with Elektra-Sonne all the way home from mid-Atlantic, and that its position when checked by periscope outside its Norwegian base was in error by only two sea-miles.
Thirdly, the rapid advance of the Soviet armies had jeopardized the safety of the U-boat training areas, located around Danzig in the eastern Baltic. Minelaying by British aircraft had already disrupted the training, as the over-stretched German minesweeping organisation finally started to show the strain. The training flotillas were forced to move westwards to Luebeck Bay towards the end of January. This was unsatisfactory, since the waters of the western Baltic are shallow, and therefore unsuitable for deep-diving trials. Worse, the area was within range of radar-fitted bombers from Coastal Command that made periodic sudden attacks on the area during darkness. Nevertheless, the efficient German training organisation continued to turn out new crews faster than U-boats could be manufactured in which to employ them.
Fourthly, as previously recounted, the U-boats were very reluctant to send signals anyway, for fear of their position being located while transmitting. This reluctance was understood, and even endorsed, by U-boat Command, but it meant that weeks of complete silence might elapse before the naval staff could grasp whether a boat had had successes, whether a patrol area might be very promising with much merchant traffic (alternatively very heavily defended with little traffic), or whether the U-boat concerned had been lost. U-boat Command was forced generally to rely on the well-tried method of dead reckoning to assess the position of a U-boat. It could be assumed to start schnorchelling as soon as it left base, then it would travel sixty-seventy sea miles per day to its patrol area, of which naturally U-boat Command was aware. The U-boat was assumed to be there until its supplies ran out, and then its course home would be plotted by dead reckoning. This created a return-by-latest date, beyond which it was likely that the U-boat had been sunk. It may be recalled that the British submarine tracking station had found dead reckoning to be an unsatisfactory method for plotting a U-boat’s path from Norway to the British coast; however Allied Intelligence was handicapped by not knowing the final destination of the U-boat.
On 17 January U-boats returning from the North Channel, the Irish Sea and the Normandy invasion area were ordered to send their situation reports from about 500 miles west of Ireland. It soon became clear that U-boat commanders were increasingly reluctant to send any messages at all, even the required passage signal from which they would then receive orders for their final patrol grid. In late February U-boat Command had commented that too many commanders were allowing their radio staff to make them believe that circumstances were unfavourable for transmission on the outward journey, but apparently there was never any difficulty about the signal on the return passage. If necessary, the crew was to be informed that the boat would surface every day to improve transmission conditions, until the radio staff agreed that they were favourable! This ruthless attitude evidently provoked a reaction from U-boat commanders, since U-boat Command on 5 March was forced to clarify with an announcement to all boats at sea that ‘we want radio transmissions once south of Iceland. But not too many, act reasonably.’ Or the enemy might be expected to react.
In short, U-boat Command was painfully aware that it was ignorant of what was happening during the Inshore Campaign, and constantly feared the worst. A report made by a U-boat back in base that its patrol area was very favourable, resulting in further boats being sent to the same area, might be out of date even before the replacement U-boats sailed. Especially since Allied defences were obviously becoming stronger and better organised around the British Isles.
Hitler directed towards the end of January that ‘the U-boat war was to be strengthened by all means and speedily intensified.’ He expected the U-boats to have a decisive influence on the war, especially when the new types working up in the Baltic were ready for operations. This message was relayed by Doenitz to all U-boat commanders on 26 January. Two days later, Hitler was again reassured that U-boats in coastal waters were achieving considerable successes. Therefore the allocation of many U-boats to the area was justified, especially since ‘shipping losses so close to the British coast must be particularly disagreeable to the enemy’. Notwithstanding January’s losses, Doenitz planned to intensify the Inshore Campaign, using newly commissioned old-type U-boats as a stop-gap measure pending the arrival of the new Type XXI boats. His reasoning was that this strategy would tie down Allied forces that would otherwise interfere with the almost uninterrupted movement by sea of large numbers of troops from Norway back to Germany, where they could be deployed against the advancing Russian and Anglo-American armies. Sinkings might also interfere with the supply chain for the western armies. Thus he ordered a ‘Spring Offensive’ using all available U-boats.
In his memoirs, published after his release from prison in 1955, Doenitz wrote that there appeared to be ‘satisfactory developments’ in the U-boat war from the Inshore Campaign by the end of January, and therefore U-boat Command had decided to send all boats commissioned in February, as they became available, to British shores. Doenitz acknowledged that this was ‘not an easy decision to make’, since the enemy was certain to increase defences around Britain. In fact forty-one U-boats sailed from Norway in February, and by the end of the month there were fifty-one U-boats on patrol around Britain’s coastline. On 15 February, Hitler was informed that the Kriegsmarine had 450 U-boats in commission, the highest total ever, of which 237 were on patrol or being prepared for operations. More than half of the 237 boats were of the new Type XXI and XXIII boats. In the third week of February, Doenitz gave instructions that ‘Dockyards are to continue to work at full pressure … As many boats as possible [are] to be ready to proceed’. This would result in an increase in the numbers of boats at sea by the end of the month with maximum priority for fuel for the Atlantic boats.
All these developments were watched through decryption with mounting alarm by the western Allies. On 10 January, they learned that the headquarters of the notorious SS organisation had prohibited all party members from any speculation about U-boat operations, and considered that this order must presage a sudden U-boat onslaught. But on 5 February, British Intelligence was able to assert that there was still no sign of large-scale intensification of the U-boat war, despite Hitler’s direct command. By 19 February, a German communiqué had disclosed that U-boats were being sent to inshore areas where the density of shipping and chances of making sinkings were the greatest, but where also the fighting was the hardest and high losses could be expected. It was not until 26 February that it had become clear that things were hotting up, with forty-six U-boats now at sea (whereas only twenty-seven on 1 February).
The Germans were also watching events unfold with trepidation. By 11 February it had become clear, from the non-return of some U-boats, that losses had mounted significantly. However, the over-inflated claims of surviving commanders meant that U-boat Command believed that some 4.4 enemy ships, mostly merchant vessels, were being sunk for each U-boat lost. Although the causes of U-boat losses were unclear, these figures justified the continuation of the campaign particularly as there were no worrying reports of new types of Allied counter-measures. Indeed, the Naval Staff had computed that figures sunk per U-boat per patrol had reached 9,000 tons by December 1944, rising to 11,000 tons in January. These figures were as high as had ever been seen, although the long transit time of submerged boats to their patrol areas was reducing the all-important ‘tonnage sunk per U-boat per day at sea’. In fact, each boat now required an average of 24 days just to reach its patrol area.
Nevertheless, Doenitz could report to Hitler on 17 February that seven U-boats had newly returned safely from British coastal waters, and that their commanders had reported weak British defences and great confidence in the schnorchel. Consequently, more U-boats were being pushed into the same areas. He stressed once again just how important it was in the New U-boat War for the boats to remain submerged continuously. The Fuehrer expressed his delight with these results, and emphasised again the great importance militarily of the revival of the U-boat campaign.
Tactics were also being modified in the light of the experience of returning boats. U-boats were warned, in Experiental 217C (30 January) that it was safer to schnorchel during daylight, in clear conditions with a flat sea when the schnorchel would be clearly visible from the air. At least an approaching aircraft could be sighted by the air periscope, whereas at night the schnorchel could still be seen from the air but not the aircraft from the periscope. Some commanders had reported accurate night bombing of the schnorchel under such conditions. All U-boats were reminded on 11 February that they must stay at periscope depth and not rely on hydrophones to detect targets. Many experienced commanders had reported that, after attacking a convoy, the best tactic was to move away as quickly as possible, and not simply to sit motionless on the sea bed. This was communicated to crews at sea on 4 March. Passage into the English Channel via the shallow waters just to the west of Ireland had to be abandoned when boats reported that the Allies had discovered the route. As losses mounted, U-boat Command directed in early March that U-boats should avoid use of the schnorchel during daylight while on passage to their assigned billets, and that schnorchelling within the patrol area itself was to be carried out at night in secluded areas, such as inlets or bays. The periscope was also to be used cautiously. Another problem was that of exhaustion among the crew after protracted sojourns in the patrol area, and on 10 April commanders were given discretion as to whether to return to base or continue their patrols under such circumstances.
As a protective measure, U-boats sent to the west coast of Britain for the Inshore Campaign were first sent to a series of waiting areas west of Ireland in February, which allowed U-boat Command to receive the latest updates from returning boats and make its dispositions on that basis. The general idea was to spread the Allied defences, rather than focus all the U-boats in just a few selected areas. However, many of the assigned patrol areas had been transmitted in the special boat-specific cipher, and some of the U-boats lacked the means to decipher it, with the result that a few U-boats found themselves patrolling barren sea areas south-west of Ireland. Two commanders were severely reprimanded by Doenitz on 19 February for their failure to enter the English Channel or the Irish Sea on their own initiative, ‘where the enemy is to be encountered with certainty’. The Allies lost the ability to decrypt current German wireless transmissions for about a week from 1 March, but the effects were not serious and by the 12th British Intelligence had noted that ‘the focus of the U-boats is now the south-west approaches (to Britain)’; one week later a further note recorded that there was less U-boat activity in March, compared with February. Many of the boats on patrol had returned to base or been sunk.
For the Germans, successes seemed to be rising too, although claimed sinkings announced by OKW (German Military High Command, using figures from U-boat Command who provided them in good faith) were well in excess of the actual figures. Tonnage sunk per month by U-boats appeared to have risen steadily from the 33,500 tons of November 1944, when the boats of the ‘New U-boat War’ first reached their patrol areas, to 259,000 tons by March 1945. As early as 21 April 1943, Doenitz had stated his belief that the Allies could not withstand losses of merchant shipping vaguely assessed as ‘100,000 to 200,000 tons per month’ for any length of time.
The true figure for March was around 67,000 tons sunk, although this month’s mismatch between belief and reality was exceptionally wide. In fact the number of U-boats actually on station in their patrol areas had steadily declined during March as the boats of the ‘Spring Offensive’ returned home. Losses were attributed predominantly to deep-laid mines, which could be avoided by remaining in shallow waters. A striking feature of the claimed U-boat successes was that all boats that had returned home had reported having made successes. Doenitz pointed up modestly to Hitler that U-boat Command was counting only claimed successes from returning boats in its reports, and not the successes that sunken boats might be presumed to have obtained. In his memoirs, Doenitz adds that the reports from the commanders returning in late February and early March appeared to have justified the decision in late January to reinforce the U-boats in British coastal waters.
Hitler maintained a lively interest in the New U-boat War, especially as it was the only front in which successes appeared to be forthcoming. Towards the end of February he asked to be provided with a short summary of U-boat operations from 1939 to the current date, and the four page document is reproduced in the Kriegsmarine archives dated 28 February. The essence of this document was that the Allied mastery of the skies over most of the Atlantic in mid-1943 had suddenly stopped a highly successful U-boat campaign dead in its tracks. The older U-boats were not really submarines at all, but just ‘diving-boats’ vulnerable to attack whenever they returned to the surface to recharge their batteries. By contrast the schnorchel boats, even the old types, were not vulnerable to air attack, and this had resulted in a ‘fundamental change’. The Allies might still rule the skies, but they did not rule the waters under the waves. The document concluded with the reassuring news for the Fuehrer that the ‘sharp weapon of the pure submarine exists, and will become even sharper with the new U-boat types’.
There was worse news from the land fronts by the end of March. The Russians had reached Danzig, the western Allies had crossed the river Rhine (the last serious obstacle to a thrust deep into Germany), and the long-feared massive bombing attacks on unprotected German shipyards had begun. This finally caused a steep decline in the construction of the new, pre-fabricated U-boat types, and completed U-boats in dockyard hands were forced to move out to sea each night in order to escape the regular air raids. The minesweeping organisation had finally completely collapsed, and there were insufficient escorts for U-boats moving from Germany to Norway. This traffic now included many boats from the training flotillas, fleeing from the advancing Russians to Norway.
No fewer than fifty of the old Type VII boats with schnorchels were now ready for deployment from Norway, the necessary diesel fuel having been scraped together in January from some of the major diesel warships (for example from the so-called ‘pocket battleships’ Luetzow and Admiral Scheer) and other warships that had been laid up. Since reported results appeared to be so good, especially from the Channel area, another thirty-eight of these old boats sailed from Norway in March. Forty more boats sailed in April, but by now Germany was desperate for military relief of any sort, and some of the boats are thought to have sailed when not in a fit condition.
But now disaster struck. The Allied escort groups had learned to anticipate U-boat tactics, decryption frequently gave away their positions – transmitted by radio to the waiting boats – and sweeps of the allocated patrol areas by the highly trained groups mopped up all the U-boats within the area. All coastal waters were saturated with Allied escorts (many being Canadian-flagged, since the threat to the east coast of Canada had virtually disappeared), and every warship that could do so was pushed out from dock to aid the effort – some ships had earlier been damaged by the constant explosion of their own depth-charges in the shallow coastal waters. Doenitz’s prediction to Hitler had come true. As an example, the 21st Escort Group was assigned to protect convoys entering the north-west approaches, but when temporarily free from this occupation the ships spent their time during March looking into every bay and inlet of the area. The result was that all three U-boats off the North Channel were sunk without giving a tell-tale message to U-boat Command, and the Minches were cleared for shipping by the end of the month. The extent of the losses slowly dawned on U-boat Command during March, as U-boats failed to return by the time allowed through dead reckoning. The survivors reported a heavy build-up of naval and aerial defences within just two hours of making an attack, and U-boats were again warned that it was essential to change position after firing every torpedo.
U-boat Command had already become anxious about progress of the U-boat campaign during March, owing to the puzzling lack of reports of U-boat attacks from British ships. The Naval High Command (SKL) noted on 29 March that: ‘The strong losses suffered in the last month on the coastal convoy routes in the area around England necessitates the temporary, partial removal of the U-boats from the English coast. Those boats already there will therefore get new operational areas.’ On 7 April Doenitz informed Hitler that the old types of U-boat were just too slow after they had made an attack to evade this rapid concentration of Allied forces, but that the new ‘electric’ boats would not suffer from the same difficulty. For this reason, U-boat Command was planning ‘to remove [the older types of U-boats] from coastal waters for the present’. The boats would be stationed further west, to try to scatter British defences. Four days later, the SKL counted the known loss of eleven U-boats in March, of which nine had been deployed in British coastal waters.
After the war, staff from U-boat Command reckoned that, given much freedom of movement, too many U-boats had chosen to select the same patrol areas in the English Channel previously reported as favourable. At the time this was not appreciated, and on 30 March and 10 April U-boats bound for the western Channel were repositioned near the Scilly Isles and off southern Ireland. On 15 April, six U-boats bound for the North Channel were also moved west, while three boats scheduled for the Irish Sea were given free choice of patrol area. Thereafter, according to Hessler in his post-war account of U-boat Command for the British Admiralty, ‘we heard practically nothing of the course of operations after March’.
Little opportunity had the U-boat crews had in which to acquire experience for the ‘New U-boat War’. Previous patrols in U-boats obviously helped, but the most experienced crews were being withdrawn to man the new ‘electric’ U-boats. The time spent by the conventional Type VIIC schnorchel U-boats in reaching their patrol area, then in locating targets in seas swept clear of shipping by the convoy system, then the long cruise home, then the lengthy refit (a month or more) of a boat ruined by corrosion externally and by smoke and dampness internally, meant that even the most successful and lucky commanders managed just two inshore war patrols from Norway before the end of the war. Each round trip took rather more than three months, including dockyard time; the ‘New U-boat War’ began in October 1944 and ended in May 1945, and therefore lasted only seven months.
