Chapter IV
Defeat in the North Atlantic

Convoy Codes explained. . .

  1. The tables turn. The U-boat seeks evasive action in attacking.

  2. A contemporary appreciation of U-boat situation in April 1943.

  3. U-boats must surprise to succeed. Löwenhertz - HX 231.
    1. The first night most favorable.
    2. Operation does not measure up. Reprimands.

  4. Adler awaits northeast, convoy but operates on southwest convoy.

  5. Rapid shifting to reset lines for northeast convoys. Lerche and Meise.
    1. Lerche - HX 232.

  6. Extra precautions, deceptions, and shipboard intercepts fail. Meise and HX 233 - SC 126.
    1. Radio deception and radio silence.
    2. Convoy voice interception.

  7. Meise divided by southwest convoys. ONS 3, ON 178.

  8. Persistent shadowing but no attack. Trotha, Meise, and HX 234.
    1. Trotha's brilliant shadowing. A one man operation.
    2. COM SUBs seeks Trotha's opinion on the failure.

  9. "Sinking" of the Ranger. Group Specht and Bülow.

  10. New and improved pattern for eastbound convoys.
    1. Only east bound convoys acceptable.

  11. But westbound convoys are taken. Fink - ONS 5. The "sound of kettle drums."

  12. Ideal situation for renewed attack on eastbound convoys.
    1. German and Allied radio intelligence.
    2. COM SUBs not aware of carrier defense? (HMS Biter)
    3. The operation and results.


  1. New evasion pattern in the northwest.

  2. Admiral Dönitz explains lack of success: Radar or Allied "wiles and technical innovations. "

  3. Groups Donau I and II and group Oder. SC 130.

  4. Last challenge.
    1. Group formation and convoy intelligence.
    2. COMSUBs will not admit defeat.
    3. U-boats are called off to prevent their slaughter.

  5. Dönitz admits defeat.


  1. The tables turn. The U-boat seeks evasive action in attacking.

    The exertion of March brought a drop in U-boats at sea during April, but there was no relaxation of Command's insistence upon the most vigorous prosecution of the war against eastbound convoys. In May, the number of U-boats patrolling the convoy lanes again reached the high mark of March. Some hard battles were fought but after weeks of the heaviest losses, U-boat Command admitted defeat. Available figures for U-boats sunk in North Atlantic convoy operations during these month's show well enough what was happening, even though the figures are approximate. Neither Allied radio intelligence nor. COMSUBs knew what had become of them in every case, except that failure to report was taken as final.

    Month U-boats lost in attacks
    on US-UK convoys
    March   4  
    April   8  
    May   18  

    The U-boat had been decisively beaten on its own field of battle. It could no longer select the conditions under which it would attack but was forced at every turn. It will be seen again and again in the following account of April-May that as aircraft defenses increased and as aircraft-surface escort cooperation improved, the plight of the U-boat became more and more hopeless. Prospect of success was relentlessly narrowed to the brief period of quick, surprise attack, which presupposed contact under very favorable conditions. The chances of favorable contacts, however, were considerably reduced by convoy routing which benefited from radio intelligence. In an effort to increase his contacts, COMSUBs once more permitted his group arrangements for eastbound convoys to be disturbed by attempts to exploit westbound convoys. Rather than let go or rest content with a short operation on each favorable contact, U-boat Command's policy was to exhaust the U-boats fighting strength in fruitless dashing. U -boats were ordered to get ahead of the convoy by sweeping around outside of the aircraft patrol range and come in at the convoy again from ahead. The preliminary task of


    getting into this favorable attack position involved exposure to surprise from the air. U-boats were intimidated and Command could offer no consistent solution for their problem. Demanding "Attack, Attack!" he tried to dismiss aircraft as something which could be warded off as a man would brush away a fly.

  1. A contemporary appreciation of U-boat situation in April 1943.

    Before proceeding with the U-boat narrative it will be helpful to review the situation as it appeared in April to both British Admiralty and U-boat Command. Admiralty noted how increasingly concerned the U-boat was with its own evasive action. In COMSUBs' messages of mid-April, two things stand out: fear and aircraft; fear not of aircraft alone, but fear of surface escorts, too, as they followed up the aircraft. In the British Anti-submarine Bulletin for April 1943 the following comments are presented: (emphasis added)

    Morale and efficiency are delicate and may wither rapidly if no longer nourished by rich success. . . individual U-boats seem to have pressed home their attacks far less effectively than in previous months. Possibly this indicates a decline in their fighting spirit, as well as some reduction in efficiency. It seems that merely to detect U-boats coming in to attack is to have the battle half won. All their efforts appear to tend to the avoidance of detection an once it is apparent that they have failed in this endeavor they seldom press home their attack."1

    COMSUBs inclined toward a similar view:

    ". . .we may assume that the enemy, after his first passage over the sub and after throwing his depth charge, throws out one or several buoys which are provided with a timing device to drop more depth charge after the lapse of half an hour. This is to make the submerged sub think that the sub-chasing


    forces are still present. In other words, bluff. Always remember that the crackling alone indicates no immediate threat. The enemy has to a large extent directed his defense against our morale, and whoever lets his healthy warrior and hunter instinct get confused and tricked is not much good in the face of the enemy's actual defense, nor is such a man able to attack, but he feels hunted and pursued wherever he is. That is the idea of the enemy's defense and propaganda in the U-boat war." (1458/1526/11 April 1943)

    Shortly afterwards he discussed another phase of antisubmarine warfare:

    "The airplane is still the most dangerous foe to the sub. In the future we must count on air power everywhere and learn to fight against it. Defense against aircraft while on the surface has succeeded well in many cases and is becoming more and more promising with increased improvement in anti-aircraft weapons. The decision whether to submerge or to remain on the surface is a question of the success of choice of the Commander. Success or failure determines here too the correctness of the measure in each case." (2245/16 April 1943)

    It should be noted that COMSUBs was trying to reduce the situation, as far as possible, to psychological terms. Confronted with the fact of surprise attack by aircraft, however, he could not formulate any consistent policy of defense and ended by reducing it, too, to the psychological realm of the Commander. To be informed that "success or failure determines. . .the correctness of the measure in each case" would be of little concrete assistance to a Commander. Unable to meet the situation with anything more and recognizing that good judgment and a daring spirit alone would not win the U-boat war, COMSUBs showed his concern by requesting "magic eye" and oscillograph experiences.2 The necessity for these reports was urgent in the development of anti-radar defense.


  1. U-boats must surprise to succeed. Löwenhertz - HX 231.

    Somewhat battered, the submarines that had chased HX 230 returned west for the next eastbound convoy. Current radio intelligence was available for the end of March and it was possible to follow the refueling task of Wolfbauer and the temporary assignments of U-boats waiting for the next group of formations. It was the usual thing: fresh U-boats and U-boats not needing fuel heading for the areas where the next group were planned. On April 1, it was known that four U-boats were to wait north of Flemish Cap and others from 55° to 59°N in mid-ocean.

    1. (a) The first night most favorable.

      The actual assignment of Löwenhertz when U-530 (Lange) sighted HX 231 at 1224/4 in area 55°N - 36°W. COMSUBs at once warned that Löwenhertz must:

      "try to come to the attack without question tonight at the beginning of darkness. Evaluation of the last great battle has proved that as a consequence of surprise and unwatchfulness of the escort the first night is always the most favorable." (1602/4 April 1943)

      In February, after its initial failure with SC 118, COMSUBs had told group Pfeil that the first night meant nothing. U-boat chances were more promising after the escort had been exhausted by the constant effort to keep the U-boats down. Apparently U-boats too could be exhausted by this process.

    2. Operation does not measure up. Reprimands.

      With the flurry of sighting reports that followed Lange's contact came frequent references to escort activity. The escorts were charging, as witness the report of Kummetat (U-572):

      Submerged at 1819 from destroyer. Rammed during attack. . ." (2045/4 April 1943)

      Despite the constant intervention of the convoy defense and the coverage by very long range aircraft, U-boats succeeded in


      maintaining contact and getting in to attack. To COMSUBs, however, Löwenhertz was talking too much.

      "Apart from shadower reports, you are using the radio too much and for messages of too great detail." (0543/6 April 1943)

      A tendency on the part of several U-boats to go after the same straggler brought the following reprimand and exhortation:

      "Despite favorable weather conditions, the results so far achieved against the convoy are completely unsatisfactory. It is not necessary for several submarines to chase one unprotected ship. The convoy is the main objective, and you must operate against it at the highest possible speed. If today during daylight there is air protection with the convoy and if contact has been made, then with the utmost strength sweep around ahead of the convoy, keeping off at a distance of 30 to 40 miles, in order to thirst against the convoy from ahead in either a day or a night attack. Be more energetic and show more toughness in taking advantage of the rare opportunity of assaulting a convoy." (1030/6 April 1943)

      Whatever renewed, activity this message may have inspired in the U-boats was summarily dealt with by the joint aircraft-surface escorts, although Otto (U-270) later claimed two freighters and Karpf (U-632) a destroyer. The last small flare of effort followed up upon Karpf's location of the convoy in 57°45'N - 26°48'W, but, low on fuel and with periscopes and torpedo tubes inoperable because of depth charge and aircraft bomb detonations, the U-boat could not capitalize on this opportunity. The total of seven ships sunk from a convoy of 61 ships was hardly commensurate with the amount of effort expended or the number of U-boats involved.

  1. Adler awaits northeast convoy but operates on southwest convoy.

    It had been appreciated since 1 April that a group was in preparation for the Newfoundland assignment and that they would take their positions in area 51°N - 41°W. Hence, when Adler's official order (1853/5) was read early on the 7th, "be in


    line 0800/7 from 54°51'N - 44°35'W to 52°57'N - 39°55'W for northeast convoy expected on the 7th," there was no surprise. Adler did not find its convoy. Instead Adler took advantage of Bülow's (U-404) contact on ON 176 at 1400/10 in 54°03'N 38°45'W. The attack on ON 176 was the first operation against a westbound convoy since the end of February to achieve even a semblance of success. U-boats met with obstinate depth charge pursuit in the Newfoundland fog and COMSUBs harangued his men for losing the convoy.

    ". . . enemy position should have been included at once in the first report concerning taking over of contact. Report it at once." (2108/10 April 1943)

    Three U-boats came through and reported but the convoy slipped away again and the operation was discontinued at 2157/12. Claims for seven ships torpedoed went in for evaluation.

  1. Rapid shifting to reset lines for northeast convoys. Lerche and Meise.

    As Adler was permitted to turn against a southwest convoy, no time could be lost in rushing up replacements for blocking northeast convoys. Twenty-eight minutes after Bülow's contact, ten U-boats were ordered at top speed to close the gap by lining as group Lerche from 54°39'N - 34°35'W to 51°45'N - 32°05'W. (1428/10) A little later, at 1558/10, new group Meise was ordered to join with a few Adler submarines that had been left to peg the southern end of the Adler line and with them to form by 0800/11 from 52°09'N - 37°05'W to 49°51'N ,. 35°25'W. Meise was to grow and grow, but at this time it counted only seven U-boats. Both the Lerche and Meise orders were in COMINCH's hands the following day, 11 April.

    1. Lerche - HX 232.

      Lerche's line was well chosen. RX 232 met the U-boats head on, Deecke (U-584) reporting the convoy at 1010/11 in 53°45'N - 33°15'W. With more reminders that U-boats must take advantage of the surprise element on the first night U-boats were ordered to:


      "Get ahead at top speed. If aircraft is too strong, sweep around the convoy in an arc. Since strong air protection is to be expected tomorrow, every sub must try by all means to be in position to attack tonight." (1707/12 April 1943)

      Contact was maintained during the following day but the weather deteriorated and at 1044/13 the order to discontinue the operation was sent. HX 232 lost three ships.

  1. Extra precautions, deceptions, and shipboard intercepts fail. Meise and HX 233 - SC 126.

    1. Radio deception and radio silence.

      The Meise line which replaced Adler on 11 April was farther to the south than its predecessor. Apparently hoping to assure contact for Meise by preventing a convoy routing that would head north and pass to the west of the current operation on ON 176, COMSUBs dispatched Uphoff (U-84) from Adler and sent him to area 53°15'N - 46°45'W. Enroute Uphoff was to transmit different kinds of messages (WW's, B'B"s, and ENIGMAs), keyed by different operators, ". . . to give the impression that several U-boats are enroute to that point." (2158/11) HX 233 and SC 126, however, were steering clear of Meise by a southerly routing and the successive measures taken to assure contact were all in vain. By the 15th Meise had grown to 24 U-boats and had moved in to the west. Lest any inkling be given of the true location of the line strict radio silence was enjoined, except for necessary contact and shadowing reports. Even here, however, U-boats were sharply criticized for the slow drawn out way in which they usually sent short signals. Not only did the manner of sending hinder accurate reception, but it provided the enemy with too many D/F bearings.

    2. Convoy voice interception.

      On the 15th Meise was still expecting at least one northeast convoy. To assist in making contact U-boats were ordered to set watch on convoy voice (2410 kcs) and report all observations. U-boats reported signal strengths of convoy voice interceptions until the 17th, and apparently contributed


      thereby to COMSUBs impression that his northeast convoy was still west of the Meise line. What actually happened is not altogether clear but the U-boats must have been intercepting transmissions from a southwest convoy. HX 233 and SC 126 were not met until they reached the area of 47°N - 22°W where some outbound U-boats ran into them.

  1. Meise divided by southwest convoys. ONS 3, ON 178.

    In addition to following the preceding adjustments and reinforcements of group Meise, radio intelligence made available on 19 April the latest composition and last line assignment of Meise ordered on 17 April in preparation for HX 234 on the 19th. It was known that 26 U-boats were patrolling from 53°45'N - 46°15'W to 49°45'N - 39°55'W and that they had been thoroughly warned to:

    ". . . keep radio silence from now on except for reports of tactical importance. Allow yourselves neither to be seen nor to be located by aircraft." (1343/17 April 1943)

    HX 234 was proceeding around the northwestern end of this line. During the night of 20-21 April ONS 3 and ON 178 were apparently forced to cut in too closely and one of them was picked up by U-boats at the northwestern end of Meise. The convoy was attacked at once. By noon of the following day, 21 April, a second southwest convoy had been contacted about 80 miles behind the first. Meanwhile, however, this churning at the end of the line had led to contact at 0924/21 on HX 234 in 56°39'N - 42°24'W. With three convoys on his hands COMSUBs permitted U-boats in the immediate vicinity to operate according to the most favorable target. As a result some 9 or 10 Meise submarines went off to search in a snowstorm. Having permitted this dispersal COMSUBs was forced to follow up with such orders as :

    "search at high speed and in big sweeps. Convoy must be found again." (2343/22 April 1943)

    The convoys had lost two ships and one escort.


    Persistent shadowing but no attack. Trotha, Meise, and HX 234.

    A few minutes after Trotha (U-306) reported a convoy on a course east at 0924/21 in 56°39'N - 42°24'W COMSUBs had ordered Meise to operate. After 10 days without finding the "expected" northeast convoys Meise was now addressed in this fashion:

    "Now go after it and see red!" (1001/21 April 1943)

    The contact was not exactly favorable in view of the U-boat disposition, but U-boats were relieved of any concern with fuel by the assurance that a supply sub would be stationed in 51°25'N - 30°15'W. They were not to break off the chase until they were down so low that the refueling station could be reached with only a margin of 5 cbm.

    1. Trotha's brilliant shadowing. A one man operation.

      Trotha lost contact temporarily when he was driven off by a destroyer, but regained it 6 hours later and, except for brief interruptions, maintained it until the operation was discontinued on the 25th. In the course of Trotha's shadowing U-boat Command tried everything he could to mass U-boats on the convoy. Outbound U-boats were put on interception courses. In commending Trotha the others were rebuked.

      "Trotha's good shadowing must not be left without results. . . This convoy must be plucked! " (1250/23 April 1943)

      And again, when the others still held back:

      "Subs are depending too much on Trotha's reports. According to Permanent Order #2, another sub must constantly report. . . " (2230/23 April 1943)

      Ordered to make submerged attacks during the day and to come in from ahead for "joint attacks" on the surface at night, the U-boats either would not or could not join Trotha. In fact,


      it was Trotha himself who finally fired at the convoy, although normally he should have waited until there was another shadower before attacking. U-boat complaints that they were being held continually under water were met with a recommendation that:

      ". . . Commanders prepare themselves increasingly to make attacks by day. In so doing, remember the Bold procedure which in recent times has been used almost invariably with success." (1531/24 April 1943)

      (NOTE - Bold procedure was a submarine bubble target).

      The operation was summed up with the obvious:

      "The best shadowing, without attacking results, is worthless." (1531/24 April 1943)

    1. COMSUBs seeks Trotha's opinion on the failure. (emphasis added)

      "Send brief situation report on following points:
      1. Last night: weather conditions, circumstances of attack, protection.
      2. Conditions for underwater attacks during the day. aircraft situation is known here.
      Explanation of failure to strike despite the fact that there are 12 submarines operating on convoy." (1639/24 April 1943)

      To this Trotha replied:

      "Ref. 1: hail, fog, rain, snow squalls, very changeable visibility. In my opinion enemy has taken ideal advantage of this by at least 3 zigzags. . . Columns are about 10 steamers long. Destroyers or escort-vessels are in gaps. . . Ref. 2: . . . in my opinion, good. (b) no opinion. " (0411/25 April 1943)

      By 25 April most U-boats which reported at all, stated that they could not reach the convoy because of the weather and


      before noon the operation was discontinued. HX 234 had lost a total of two ships, both stragglers. Three U-boats were sunk.

  1. "Sinking" of the Ranger. Group Specht and Bülow.

    Pressing hard, COMSUBs was now sending U-boats fresh from port to form new groups west of 30°W. While Meise trailed HX 234 and searched for ONS 3 and ON 178, the formation of Specht was followed in current traffic, as it lined up with 17 U-boats east of Flemish Cap in expectation of SC 127. Specht's was the first line in the northwest Atlantic to go as far south as 44°N. Its position had probably been influenced by reconstruction of the route taken by HX 233 and SC 126 after those convoys had been contacted by boats outbound from Biscay. At the same time 11 U-boats from port were gathering north and east of Specht and group Amsel.

    During the course of the run with HX 234, Meise reinforcements in the form of new U-boats outbound from the north had crossed ONS 4 and ON 179. Disappointed by SC 127 COMSUBs ordered that the westbound convoy be followed and hastily moved Specht north and east to intercept. Specht's new position was known and the convoys evaded the line but not without an engagement of arms. Bülow (U-404) came upon an aircraft carrier. . At 0817/25 he claimed to have heard 4 hits and several heavy explosions. "Ranger possible." The jubilant COMSUBs immediately replied "Good! Good! Report whether in your opinion aircraft carrier was sunk." (1423/24) To which Bülow said "Sinking assumed." (1819/25) Bülow was promptly awarded the Oak Leaves to the Knight's Cross and called home.

  2. New and improved pattern for eastbound convoys.

    As though rededicated to the one thing necessary - the destruction of eastbound convoys - U-boats were arranged early in May in the most striking pattern yet seen in the North Atlantic. It was the most inclusive in its coverage of outbound routes. There was no lack of U-boats and all of them were in formation west of 37°W. Beginning in the area south of Greenland Command had crossed the northerly routes with a combined Specht-Star line of 31 U-boats, slanting from 56°30'N - 47°15'W to 54°N - 37°W. Amsel, 23 in all, was broken into four parts: I) north of Virgin Rocks; II) north and a little east


    of Flemish Cap to cut off routes that might miss Specht-Star; III) east of Flemish Cap; IV) southeast of Flemish Cap. Realizing that convoys had been escaping his northwest Atlantic concentrations by southerly routing, he had now set things right and plugged every hole. Exact positions were not known but on the basis of available information and an appreciation of the new pattern it was estimated on 1 May that by 3 Mayall routes would be blocked from 53°N - 48°W around to 46°N - 38°W.

    1. Only eastbound convoys acceptable.

      When Hasenschar (U-628) sighted smoke clouds in 51°N 45°45'W on 1 May, U-boats were to hold off unless the convoy course proved to be east. When this proved to be the case both Specht and Star were ordered to attack. COMSUBs refused to believe that contact could be lost and demanded:

      "as soon as weather improves, all submarines must get at convoy as fast as possible. With 31 submarines, something can and must be accomplished. " (2215/2 May 1943)

      However, nothing was accomplished. Interest suddenly shifted to the opposite direction.

  1. But westbound convoys are taken. Fink - ONS 5. The "sound of kettle drums."

    Specht and Star were combined into new group Fink - 27 U-boats stretching from 56°45'N - 47°12'W to 54°09'N 36°55'W in expectation of a southwest convoy. Again Hasenschar made the first contact in 55°45'N - 42°55'W but reported the convoy on a northerly course at 2018/4. An hour later Gretschel (U-707) assumed that he had sighted the same convoy but was certain that its course was south. Hasenschar's next report confirmed this fact and COMSUBs, convinced that they had expected convoy, ONS 5, urged the whole group on:

    "I am sure that you will fight with the toughest action. Do not overestimate the enemy, but strike him dead. . ." (2213/4 May 1943)


    The attacking force was increased by Amsel I and II which were moved up from the south. Contact was maintained and reported with almost no lapses throughout the brief and harsh battle. By noon of 5 May, five U-boats claimed to have sunk nine ships. After weeks of patrolling distinguished only by very minor successes, COMSUBs at last had reason to hope for a victory:

    "Immediately after nightfall the sound of the kettle drums must begin. Hurry. Otherwise there will be nothing left of the convoy for the 40 submarines. The battle will not last long because of the short sea area which is left. Therefore, use to the full every chance with all your energy." (1034/5 May 1943)

    As a further precaution:

    "two submarines which have contact at about 2300 are independently to send beacon signals, so that all submarines in the vicinity of the convoy may be led to it. All must utilize this great opportunity tonight." (1916/5 May 1943)

    "Tonight's opportunity must in no event be allowed to be spoiled by aircraft before the beginning of darkness. Subs whose antiaircraft armament is clear, remain on the surface in the presence of aircraft, and shoot. Then the plane will soon stop attacking." (2035/5 May 1943) [emphasis added]

    Subsequent contact with independents and small groups led to the conclusion that the convoy might possibly have broken up. It must have been a source of no small satisfaction to COMSUBs to be able at this time to transmit the order:

    "if there are no more steamers to shoot at, then sink escort vessels, using magnetic fuzes." (2333/5 May 1943)

    If ONS 5 suffered heavy losses - 11 ships sunk out of 42 the attacking groups also sustained a considerable amount of damage. Out of 40 U-boats six were sunk. Two U-boats were rammed, one fatally, and numerous others were forced to


    discontinue operation in order to repair damages resulting from depth charge and aircraft bombs. COMSUBs did not yet know the price he had paid when he signaled his review of the battle:

    "This convoy battle has once again proved that conditions (for action) on the convoy are always most favorable at the beginning. He who uses fully the moment of surprise in the first night and pursues the attack with all his means, finds success. After the first blow it is always more difficult, and in addition the uncertainty of the weather comes into the picture, as in the case in which fog frustrated the great opportunity of the second night. Hasenschar is king of the marksmen." (1041/7 May 1943)

  1. Ideal situation for renewed attack on eastbound convoys.

    1. German and Allied radio intelligence.

      Undecided about disposition of the ex-Fink submarines after the ONS 5 operation, Command's mind was suddenly made up by intelligence on an outbound pair of east convoys, "one fast and one slow," HX 237 and SC 129. Available Fink submarines were formed with Amsel I and II as Elbe while Amsel III and IV as group Rhein held their former position. 29 U-boats were in line from 52°45'N to 43°57'N east of Flemish Cap. Conditions had never been more ideal for U-boat Command and he apparently expected much from the operation which followed. U-boats were even taken off the England-Gibraltar lane (group Drossel) to take advantage of the excellent opportunity which had been offered by German communications intelligence. No U-boat group operation of which we have any record was so evidently guided by continuing intelligence of convoy movements. With 36 U-boats, including Drossel, the convoys should have been enveloped in mid-ocean south of 45°N in a destructive force like that of March.

      The Amsel line was known through Allied radio intelligence and the convoys were being diverted well to the south when German radio intelligence discovered the diversion in time to affect an interception. When Forster (U-359) made


      first contact on HX 237 in 41°09'N - 36°54'W. COMSUBs ordered Rhein to:

      "Go to it like Blücher." (1328/9)

    1. COMSUBs not aware of carrier defense? (HMS Biter)

      Loss of contact on the afternoon of the 9th brought a message from COMSUBs which is of particular interest because of its implication as to the convoy's defense:

      "Convoy bound for England. Later courses must be more north than east. You must intercept and attack the convoy as quickly as possible in this area where only slight air protection can reach it. In succeeding days it will be harder and harder." (1855/9 May 1943)

      If COMSUBs had assumed that the convoy would not have effective carrier aircraft defense, he was corrected when Hackländer (U-454) reported a carrier plane in 42°03'N 32°30'W.

    2. The operation and results.

      As U-boats fell behind HX 237, U-boat Command reorganized Elbe to intercept SC 129, leaving HX 237 to Drossel, which was to intercept at the straggler rendezvous points known to the Germans from decryption. Interception was made but the attack was abandoned on 14 May. The double operation cost the convoys nine ships, of which seven were stragglers. But the U-boats had been outfought. At least three U-boats were sunk. U-boats had had to pull off in search of their own damaged members.

  1. New evasion pattern in the northwest.

    During the course of the Rhein-Elbe-Drossel operation, strange things were happening in the old hunting ground south of Greenland. A confusion of small groups was formed: Iller, Lech, Isar, Inn and Nab. Containing many inexperienced U-boats, the groups did not seem to know quite what was expected of them. An attempt to combine them in groups


    Donau I and II for an operation on ONS 7 failed, possibly because the shadower, a U-boat coming out on its first cruise, was sunk too soon. The purpose of the small formations was evident as a means of evading detection, but once reformed for operation the U-boats seemed helpless.

  1. Admiral Dönitz explains lack of success: Radar or Allied "wiles and technical innovations."

    "By use of his radar, the enemy has now once more gained a few lengths on us in his effort to deprive the U-boat of its most important attribute, its invisibility, I am fully cognizant of what this has meant for you in your difficult battle with enemy escort and defense. Be assured that with all my strength as Commander in Chief I have undertaken and shall undertake every means at all possible to alter this situation as soon as I can.

    Experimental stations in and out of the navy are working to improve your arms and instrument equipment. I expect of you that you will continue your determined fight against the enemy, and that against his wiles and technical innovations you will pit your ingenuity, your ability and your obdurate will to dispose of him no matter what he does. In the Mediterranean and in the Atlantic, commanders have proved that the enemy even today has weaknesses at every turn and that his auxiliary devices are in many instances by no means so effective as they at first appear to be, provided that one is determined to achieve something in spite of them. I believe that I shall soon be able to give you better weapons for this hard battle of yours." (2258/18 May 1943), (0206/0621/19 May 1943)

  2. Groups Donau I and II and group Oder. SC 130.

    Two further attempts were necessary before Dönitz was convinced that even "determination to achieve something" would not make up for the U-boats lack of invisibility. With Donau I - II and Oder, 33 U-boats were in position to receive SC 130 on 18 May. After Koch (U-304) had established contact in


    54°45'N - 36°45'W. Command hinted at a further reason for the U-boats decline, inexperienced captains:

    "Since observations concerning the nature of defense and conditions for attack are of particular importance for other submarines, the experienced older commanders must report immediately any new data, so that command can give pointers." (1150/19 May 1943)

    The "pointers" came in this fashion:

    "Because of the current absence of shadowing reports, it is assumed by Command that it is impossible to keep contact with the convoy on account of aircraft. Therefore as soon as a sub has determined for itself the position of the enemy, move off and, remaining beyond the close air-escort. . .sweep around ahead of convoy at top speed, in order to submerge ahead of convoy for a daylight attack. If during the time sub is sweeping around convoy there continue to be no shadower's report for a period of more than 2 hours, then zag briefly up to the convoy and report." (1900/19 May 1943)

    Gretschel's (U-707) report is typical of transmissions during the operation: "Continuously forced under." (1945/19) By 0438/20 when Poel (U-413) reported land-based aircraft and most of the U-boats were trailing far behind the convoy, further operation was considered hopeless. Thereafter all U-boats were cautioned to observe strict radio silence so that Mässenhausen's (U-258) transmission of dummy traffic on his voyage home would simulate a stream of returning U-boats. A line had already been set up for HX 239. Mässenhausen, however, had already been sunk.

  1. Last challenge.

    1. Group formation and convoy intelligence.

      While 20 of Donau's submarines attempted feebly to follow SC 130, all remaining submarines in the NW Atlantic (22) were formed as Mosel from 54°45'N - 43°15'W to 51°45'N - 36°25'W in anticipation of HX 239 beginning 2000/21. Two


      more returning U-boats were ordered to send dummy traffic. HX 239 was being routed to the south of the Mosel line when German decryption recovered a straggler rendezvous dispatch for the first diversion route. Mosel was rushed east southeast to intercept.

    1. COMSUBs will not admit defeat.

      There was no evidence of defeatism in COMSUBs message to Mosel before the coming operation, but rather a refusal to admit the possibility of defeat:

      "With the last two North Atlantic convoys we have gotten nowhere and in the case of the last one the full moon was a very important factor. Now if there is anyone who thinks that combating convoys is therefore no longer possible, he is a weakling and no true U-boat captain. The battle in the Atlantic is getting harder but it is the determining element in the waging of the war. Keep yourselves aware of your high responsibility and do not fail to understand that you must answer for your actions. Do your best with this convoy. We must smash it to bits. If the circumstances permit, do not submerge from aircraft. Shoot and ward them off. Make surface escape from the DD whenever possible. Be tough, get ahead and attack. I believe in you." (1910/21 May 1943)

    2. U-boats are called off to prevent their slaughter.

      Bahr (U-305) contacted a destroyer at 1045/22 in 51°09'N - 34°55'W but was bombed by aircraft and suffered heavy damages. Johannsen (U-218) was continually forced under by aircraft. Becker (U-218) located the convoy in 50°45'N - 32°35'W, but only by means of hydrophone, and reported continuous Asdic and crack gear. Shamong (U-468) was bombed and later pursued with depth charge. Although both Mosel and Donau were now in the vicinity of the convoy, the operation was called off at 1043/23 despite the fact that the majority of U-boats reported a sufficient amount of fuel and all torpedoes and the convoy was still in sight. It is possible that Hungerhausen's (U-91) report of rescuing survivors from U-752 (Schroeter) may have influenced the


      decision. Eight U-boats had been sunk in the attempt on SC 130 and HX 239.

  1. Dönitz admits defeat.

    The immediate effect of the HX 239 operation was apparent in the withdrawal of U-boats from the North Atlantic on the following day, 24 May. In a series of messages to all U-boats, the Grand Admiral explained:

    "1. Our heavy submarine losses in the last month are to be traced back predominantly to the present superiority of enemy location instruments and the surprise from the air which is possible because of that. More than half of all losses have occurred through this surprise, and indeed on advances and returns as well as in the operational area in attack dispositions. The losses in battle against the convoys themselves were in comparison slight except for one case, in which particularly unfavorable conditions prevailed. A part of these losses, too, resulted from aircraft.

    2. The momentary situation as concerns enemy aircraft and enemy radar must be bridged over by special precautionary measures enroute and in the waiting disposition, meanwhile making the best of other disadvantages. Orders for this have been issued. In that connection I will bring about further results in the choice of the attack areas.

    3. My whole energy is engaged in the improvement of our own ortung3, defense against ortung, and anti-aircraft arms. This task is being worked on the maximum application at all our stations. Practical results will come forth in very short time. The time until then must be passed with cunning and caution on cruise and while waiting, but with your old inexorable severity in the battle itself." (1753/1842/2032/23 May 1943)


Groups Rhein, Elbe, and Drossel - HX 237 and SC 129
May 1943


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1. Admiralty, "The Monthly Anti-submarine Report," CB 4050/43(4), British Sources, Operational Archives/Naval Historical Center, Washington, D.C.

2. "Magic Eye" was an additional radio receiver that could be used with the search receiver and presented a visible output.

3. "Ortung" literally means location but in U-boat message traffic it normally referred to radar.

Transcribed and formatted for HTML by Chuck Roberts for the HyperWar Foundation