Chapter IX
U-boat's Defeat Made Emphatic

  1. Renewal of North Atlantic offensive was doomed.

  2. Nullification of U-boat counter-devices.

  3. Problem of the elusive convoys and the ever present aircraft.

  4. Change in group pattern: the crescent shaped formation.

  5. Convoy escorts and new U-boat tactics.

  6. The onset: Group Leuthen - ON 202 and ONS 18.

  7. The relapse.


  1. Renewal of North Atlantic offensive was doomed.

    The resumption of attacks against North Atlantic convoys by U-boat groups began in September 1943 with high talk of victory. Its failure became apparent after a brief success. It so happened that the renewal of the U-boat offensive was approximately timed with the current and solid reading of U-boat traffic which characterized the remainder of the war. After several months of difficulty in the summer of 1943, the German system had been mastered. Following the initial four days of Leuthen's success, U-boat dispositions, areas to be patrolled, and every shift of lines could be anticipated by radio intelligence. And, unlike the situation which prevailed during the spring offensive of 1943, war vessels and aircraft were available for direction to the scene of impending operations to meet the U-boats as they searched for their targets. The convoys in question were being regularly diverted away from danger.

  2. Nullification of U-boat counter-devices.

    This offensive never had a chance, notwithstanding the new and improved U-boat counter-devices, innovations in tactics, and the special services which had been prepared during the summer to overcome the superior Allied measures which were believed to have been the cause of defeat in the spring of 1943. Great things were expected of the new acoustic torpedo, the "Zaunkönig," which was to clear out the escort so that U-boats might get at the merchant vessels. A number of escort vessels were sunk by this torpedo, but knowledge of the torpedo's limitations and the streaming of the "foxer" gear tended to ward off its destructive power. The new radar search receivers failed to protect against surprise attack from the air.

  3. Problem of the elusive convoys and the ever present aircraft.

    The convoys could not be found, in spite of the use of every possible boat, including some hardly sea worthy, of very long range aircraft operating as far as 20°W from Norwegian


    and French air fields, of intelligence gleaned from analysis of convoy voice traffic by special B-Dienst personnel aboard the U-boats, and from an occasional decrypted convoy routing dispatch. Instead of finding the convoy, the U-boats were themselves found by Allied forces. Command continued to repeat this:

    "Founded assumption . . . that the enemy air reconnaissance, using location methods which in part we have not yet been able to pick up, has contacted our line arrangements . . ." (1903/13 November 1943)

    as his explanation of the U-boats loss of invisibility. To reduce the possibility of being spotted by ubiquitous radar equipped aircraft, U-boats were ordered to keep radio silence except for messages of the utmost tactical importance, to refrain from using beacon signals, and to cease the use of the GSR equipment by which they attempted to determine whether or not they were being contacted by radar. It was feared that GSR was giving off radiation which in turn were being intercepted by Allied receivers, and being used to locate U-boats. Against D/F an elaborate off-frequency system was inaugurated.

  1. Change in group pattern: the crescent shaped formation.

    These measures proved of no avail. A major change in group formation was introduced. Instead of concentrating all U-boats of a group in an unbroken line, the new plan called for a crescent shaped formation, the U-boats being grouped in several short lines with considerable lines. Single scouting submarines were placed further west, opposite of the gaps, while a refueler, behind the lines, backed up the whole complex. Three purposes were served by this arrangement. First, every possible convoy lane in a given area was covered. Second, the majority of the group was protected somewhat from attack if one or two U-boats of one short line were discovered. In such an event, the Allies would presumably be led to believe that they had located the main body, and the remaining short lines would remain undetected. Third, the presence of a refueling U-boat behind the lines (in itself an indication of the importance attached to these operations since refuelers were at a premium), obviated long trips for refueling,


    to the delay of operations, and allowed the U-boats to remain in patrol positions for a long time.

  1. Convoy escorts and new U-boat tactics.

    Not only aircraft but surface vessels became a force to be reckoned with the fight for survival of the U-boat. With the increase of escort vessels and anti-submarine groups, the U-boat was forced underwater and held there, if not destroyed. Frequently compelled to strike blind, unable to surface in the midst of a convoy and sink the cargo carrying merchant ships as they passed in line before him, the U-boat was ordered by Command to change tactics. U-boats, operating in pairs, were first to dispose of the escorts, and then to attack at the heart of the convoy. One U-boat was to draw the attention of the escorts away from the ships they were guiding, while the other made his way into the unprotected convoy. The acoustic torpedo was especially designed for use against pursuing escort ships, since as the ship weaved back and forth, the torpedo followed.

  2. The onset: Group Leuthen - ON 202 and ONS 18.

    By the middle of September, 21 U-boats had been assembled to form the first group of the renewed offensive, Group Leuthen. The group was to be ready for action by 2000/20 September, in a line from 59°45'N - 29°00'W to 54°25'N - 26°00'W to operate on westbound convoys only. Contact was made at 0400 on the 20th as expected, and considerable success was achieved. Acting on instructions to attack first the escort vessels, by the afternoon of the 21st, the U-boats claimed the sinking of seven destroyers. (From records available, four escort vessels are known to have been sunk in this action.) Contact was gradually lost during the 21st but regained in time for intensive operations during the 22nd and 23rd. The convoys were now prepared, however, and, with a thinning of a fog which had prevailed, aircraft were brought into action so that the submarines did not achieve the full success against the merchant ships which they had anticipated. In the late morning of 23 September, Command ordered Group Leuthen to cease operations and withdraw eastward. The action was considered a great victory, a vindication of the U-boat. From 10 to 15 destroyers and eight


    merchant ships were claimed sunk. Actually, it is believed that four escorts and seven merchant ships were the total casualties. Three U-boats were sunk in the course of the engagement. Success for the Germans ended with this operation. The continuation of group. action against North Atlantic convoys brought them only disaster.

  1. The relapse.

    1. Disappointing records of Groups Rossbach and Schlieffen.

      Attempting to repeat his previous success, Command formed Group Rossbach on 26 September. The expected convoy was diverted to the north, and escaped completely. Despite further northern shifts of the line, each succeeding convoy passed unscathed. On 9 October, the group was disbanded, having failed to accomplish the task set for it by Command, who had ordered: "Smash the destroyers, sink the ships. Make up for your long wait." The results achieved by Group Schlieffen, the last mid-North Atlantic group in the old style, were even more disappointing. Placed, on 16 October, directly across the routes of two convoys, the group gained good contact with one, but managed to sink only one merchant ship.

    2. Formation and failure of Groups Siegfried, Körner, and Jahn.

      Innovations, later to become more marked, may be seen in the disposition of the next groups formed, Groups Siegfried, Körner, and Jahn. Instead of lying across the paths of convoys in the area of 30°W, exposed to strong aircraft patrols based on Iceland and Greenland, these groups were set up for eastbound convoys off Newfoundland. On 24 October, Group Siegfried was formed in the old style, but in the new position. The Germans sources of information failed them, however, and the awaited convoy passed far to the south.


    1. Group Tirpitz and the crescent arrangement.

      Late October, considerable Anglo-American convoy traffic off Canada was routed in two lanes, one running due east approximately along the 41st parallel, the other in a roughly northeasterly direction for the Virgin Rocks. To intercept this traffic COMSUBs disbanded Group Siegfried and formed Groups Körner and Jahn on the last day of the month. Three days later these were replaced by Group Tirpitz, a crescent arrangement of five short lines with single scouting submarines opposite the gaps. This marks the first appearance of the new type of formation. Although designed to facilitate the location of convoys, traffic passed successfully north or south of these groups, and on 7 November, the whole pack was withdrawn. The aircraft patrol was too strong.

    2. Group Eisenhart and the eastward withdrawal of U-boat groups.

      The eastward withdrawal of U-boat groups which was to continue until groups were stationed to the east of Rockall began with the formation of Group Eisenhart on 9 November. Small groups formed three lines in a checkerboard pattern that covered a great band of the North Atlantic. The new grouping of U-boats was now completely evident, and again failed in its purpose. Convoys slipped around to the south. With this move the offensive against Anglo-American convoys which had been in progress since late September was temporarily abandoned.

    3. Two refuelers lost.

      The attempt to operate groups once more in the mid-North Atlantic cost the U-boat navy two, U-tankers, both sunk at rendezvous' in October by U.S. Navy CVE's. The number of supply submarines, was again reduced to two, the number which had been available at the end of August.


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