The U-boat War 1939 - 1945

Discussion in 'The War at Sea' started by Peter Clare, Jul 26, 2011.

  1. Peter Clare

    Peter Clare Very Senior Member

    The following document is taken from 'German Naval History. The U-boat War In The Atlantic 1939 - 1945' It gives a German perspective of the last few days of peace and the final preparations for war. I will, from time to time add more details related to the U-boat war but not necessarily in chronological order. If others wish to contribute please feel free to do so.


    Mobilisation and U-Boat strength and state of readiness prior to the outbreak of war

    At noon on 15th August, 1939, the Naval Staff Operations Division in Berlin called the office of S.O. U-boats in the tender Hecht at Kiel and announced that " an officers' reunion for U-boat officers was to take place on Saturday, 19th August." This message was a cover for commencing certain U-boat preparations to meet the deteriorating
    international situation. U-boats fit for Atlantic operations on 19th August were to proceed to waiting positions in the area west of England and the Iberian Peninsula.
    In Fall Weiss (the sudden and effective destruction of the Polish Armed Forces) the German Navy's task was to cut off the Polish naval forces, to control the merchant shipping and to carry out unobtrusive reconnaissance and defensive operations to prevent enemy forces from penetrating into the Baltic and the Kattegat. The part to be played by the U-boats was defined in a directive issued by the Commander-in-Chief of the Navy, and included the following tasks :‑

    BALTIC : Minelaying and patrols off Hela, reconnaissance outside the Gulf of Finland, the Gotland area, the Irben Strait and the Kattegat—by 16 boats (Types II and VII).

    NORTH SEA : Seven boats (Type II) to occupy waiting positions east of the English Channel, constituting an unobtrusive defence against possible intervention by the Western Powers. In the event of war these boats were to lay mines off the French and British Channel ports.

    ATLANTIC : All available "Atlantic " U-boats (Types I, VII and IX) were to proceed to waiting positions west of England and the Iberian Peninsula. In the event of war with the Western Powers they were to operate against merchant shipping in accordance with the new Prize Regulations, until the danger areas were announced.

    All operational orders for these tasks had been formulated by S.O. U-boats between the end of July and 12th August, and by the 15th August, 56 commissioned boats were available, while another was expected to be commissioned by the end of the month. The distribution of the various types and their state of readiness are shown in the following table :—

    Type II 250 Tons Coastal Boats (30)
    Training boats. (9) U1, 2, 3, 4, 5, 6, 7, 8, 10,
    Still under training. (4) U 56, 57, 58, 59
    Still undergoing trials after commissioning. (2) U 60, 61
    Not yet at operational readiness. (1) U 11
    Ready within 14 days. (14)

    Type VII 500 Tons Atlantic Boats (18)
    Training boats. (1) U 36
    Still under training O
    Still undergoing trials after commissioning. (1) U 49
    Not yet at operational readiness. (1) U 51
    Ready within 14 days. (15)

    Types I and IX 700 Tons Large Atlantic Boats (8)
    Training boats.0
    Still under training. 0
    Still undergoing trials after commissioning. 0
    Not yet at operational readiness. (2) U 25, 42
    Ready within 14 days. (6)

    By including the training boats U.1, 3, 4, 5, 6, 7 and 36 which would shortly be ready for operations and by curtailing the training of U.56-59, ten more Type II boats and one Type VII boat would be conditionally ready for operational service. Thus by the end of August a total of 46 boats, of which 22 were capable of operating in the Atlantic, was ready. They comprised twenty-four Type II, sixteen Type VII and six Types I and IX. The proportion of 46 operational boats out of a total of 56 was exceptionally high. The emergency coincided with a high state of readiness of both boats and crews, with very few boats undergoing training.

    Organisation of the U-Boat Command

    To meet possible developments with Poland the U-boats were mainly concentrated in the Baltic, and an organisation, previously devised by the Naval Staff for this eventuality, came into force on 18th August, whereby Commodore Dönitz and his staff were embarked in the parent ship Erich Wassner at Kiel, and the ship proceeded to Swinemiinde on 22nd August. At this time the Commodore was a member of the German Naval Staff, and also in operational control of the U-boats in the Baltic (S.O., U-boats, East) and of the U-boats assembling for Atlantic duties. The operational command of U-boats in the West was vested in Lieut.-Comdr. Ibbecken at Wilhelmshaven. He was then in command of the 2nd U-boat Flotilla, which together with the 1st U-boat Flotilla was assigned to operations in the North Sea and the English Channel.
    This organisation remained in force until it became clear that the conflict would not be confined to Poland. Should the situation in the West deteriorate, Dönitz was to proceed to Wilhelmshaven, where he was to take charge of all U-boat operations outside the Baltic.
    This change actually occurred on 31st August, when the commitments of the Baltic U-boats had decreased, owing to Germany's non-aggression pact with Russia and because in the meantime the three Polish destroyers had escaped to the West.
    By now political relations with the Western Powers had reached a crisis. When Dönitz arrived at Wilhelmshaven he took over as S.O. U-boats (West), leaving Commander Schomburg at Swinemiinde, in charge of Baltic operations.
    Disposition of the Boats during the Emergency Period
    The shifting of concentration to the West can be seen from the following table of dispositions during the emergency period :—


    BALTIC......... NORTH SEA............ ATLANTIC

    14 Type II.... 7 Type II also....... 18 Types VII, I and IX
    3 Type VII.... 4 training boats (to arrive from the Baltic on 30th August)

    After the conclusion of the Non-Aggression Pact with Russia on 23rd August, seven boats (Type II), hitherto employed on reconnaissance duties in the Baltic, were released to the North Sea.


    BALTIC......... NORTH SEA............ ATLANTIC

    7 Type II...... 14 Type II also....... 18 Types VII, I and IX
    3 Type VII.... 4 training boats by 30th August

    After the three Polish destroyers had broken out from the Baltic, the three Type VII boats there left for Wilhelmshaven. The four training boats (three Type II, one Type VII) arrived in the North Sea on 30th August.


    BALTIC.......... NORTH SEA........... ATLANTIC

    7 Type II....... 17 Type II............. 21 Types VII, I and IX
    ....................1 Type VII


    On receipt of the warning on 15th August, Commodore Dönitz was on leave in Bad Gastein and returned the following day. The necessary action was taken by Captain Friedeburg, the Chief of Staff, who stopped all training exercises and recalled all boats to their bases to be equipped for war. The Third U-boat Flotilla and the U-boat Training Flotilla were allowed to continue training until 19th and 26th August respectively. As had been expected, the manning and fitting out of the boats and other preparations went according to plan. Difficulties were caused by inadequate stocks of war torpedoes. Prior to 1939 S.O. U-boats had more than once drawn attention to this deficiency.
    The excessive number of orders and code-words in the various offices proved a disadvantage. The preparatory plans had foreseen all eventualities, but in the execution these code-words were occasionally disregarded, thereby causing confusion. The change-over from peace to war cornXmunications also caused some inaccuracies and delays in transmitting information. For example, a vital order to S.O. U-boats to be ready for action on the evening of 22nd August was received 24 hours late, and then only verbally. It should be recorded that eager as the U-boat crews were to give battle, they felt that the Government would do everything possible to find a peaceful solution to the crisis. An entry in the War Diary of S.O. U-boats for 21st August states :‑
    " The particularly confident attitude of the crews deserves mention. In my opinion it is a sign of the great trust which the majority place in the Government's policy."

    Survey of the Situation by S.O. U-Boats

    When war with Britain and France broke out on 3rd September, the situation could be summed up as follows :‑
    " It is evident from the political situation and from Britain's inherent tenacity that this will be a long war.
    " Britain is completely dependent on her sea trade for food and raw materials, and above all for building up her military strength. The German Navy's task therefore is to attack the merchant ships carrying these supplies and, if possible, to disrupt them. This means that despite the unfavourable strategic position of our Navy and its considerable inferiority in strength, the battle must be actively waged from the first day.
    " No effort on the part of Germany could enable her to catch up with Britain's immense lead in naval construction. Germany cannot hope to compete for naval supremacy. Her only course is to launch a direct attack on enemy sea communications. Apart from the few surface ships fit for long-range operations, only the U-boats are available for this purpose. They alone are capable of penetrating to the main British trade routes in face of the British superiority in surface forces.
    " What is the position as regards U-boats ? Until the end of 1938 neither the Government nor the Navy had considered Britain as a possible enemy. The Navy had been planned as a homogeneous fleet, and the U-boat arm had been built up within that framework. Thus today at the outbreak of war, the German U-boat tonnage has not even reached the 45 per cent of British tonnage allowed by the Naval Agreement of 1935 (that is, 72 boats) and is far short of the 100 per cent permitted in 1938, which would have given Germany 129 boats of various types, large and small (4). We have today the totally inadequate number of 57 commissioned U-boats, and an inadequate construction programme. Neither the existing forces nor those to be expected from the building programme are sufficient to obtain decisive results against British shipping .

    " Thus three tasks face the U-boat Command :‑

    (A) to plan and to carry out large-scale expansion so that it may be possible to disrupt British sea trade during a war expected to be of long duration ;
    (B) to dispose the available forces for maximum results at an early date ;
    (C) the operational control of the available forces."

    Proposals for a Large-Scale Expansion of the U-Boat Arm

    On 28th August, during the emergency, S.O. U-boats had submitted to the Commander-inXChief of the Fleet—Admiral Boehm--proposals for the expansion of the U-boat arm. The ComXmander-in-Chief gave these proposals his backing in forwarding them to the Naval Staff (5). Envisaging a war between Germany and Britain, Donitz had urged the raising of the U-boat strength to at least 300 boats of Type VII and Type IX, with the addition of a number of special large boats. The present U-boat programme was totally inadequate. He wanted to establish within the Naval Staff an organisation with far-reaching powers of priority, responsible only to the Commander-in-Chief of the Navy for expanding the U-boat arm.
    On 4th September, S.O. U-boats explained his memorandum to Admiral Raeder, CommanderXin-Chief of the Navy, at Wilhelmshaven. After reading the plan the Commander-in-Chief confirmed that a large-scale programme of U-boat construction was intended, and he wished to make a senior officer responsible for carrying it out. He asked S.O. U-boats for his opinion on the appointment of Rear Admiral v. Arnauld de la Perriere (retired) to the post, adding that he did not wish Donitz himself to hold it.
    The following is quoted from the minutes of the conference in the War Diary of S.O. U-boats, 9th September, 1939 :‑
    " I replied that I would give my opinion on the following day, as an appointment of this kind would have far-reaching implications. I hold that this post should be occupied by me. As an active service officer I have directed the training of U-boats from the beginning and am known to the personnel. . . . All efforts will be in vain unless we can rapidly build up our numbers, and this task now becomes the most important of all, which should be under the direction of an officer with expert knowledge of the theory and practice of U-boat warfare."
    Raeder, however, decided that Dönitz was indispensable for the control of actual operations, and could not be spared for the task in Berlin. Eventually it was decided on Dönitz's recomXmendation to give Captain Siemens the supervision of the building programme, and this officer also became U-boat Staff Officer on the Naval Staff in Berlin. In the course of the first year of war it became apparent that he was merely Head of a Department, without executive authority, and this was disappointing for the U-boat Command.
    Raeder's decision was probably right, for Dönitz was certainly needed to control operations, and his personality was directly responsible for the ultimate achievements of the U-boat War (6).
    After consulting S.O. U-boats, the Naval Staff listed their requirements for expansion on 9th September, 1939, and the first wartime building programme was drawn up by the Constructional Office in October.

    Disposition of U-Boats

    Type II boats were limited by their radius of action to the North Sea, the east coast of England and the Orkney and Shetland areas. Type VII boats could operate in the area west of England as far as 15° W., including Biscay. Type VIII boats had sufficient range to operate off the west coast of Spain, as far as Portugal. Type I and Type IX could operate as far as the Azores and Gibraltar and were capable of penetrating into the Mediterranean for short periods.
    According to their radius of action, the boats were therefore divided into three groups.
    All small Type II boats were to operate in the North Sea and off the English coast, including the Channel. If necessary, Type VII boats could also be sent to this area. This group was under the control of Dönitz, as S.O. U-boats West. In view of their escort duties in the North Sea and on their outward and return journeys, the boats' movements had to be co-ordinated with the operations of the surface forces in Group West's command.
    Type VII and Type VIII boats were to operate on the North Atlantic trade routes ; off the North Channel and in the Irish Sea, the St. George's Channel, the English Channel, and the Bay of Biscay.
    The few Type I and Type IX boats were to take up more distant positions as far as Gibraltar, on the traffic routes between the Mediterranean and Britain, and Capetown—Sierra Leone—Britain.


    During the critical days before the annexation of Czechoslovakia in 1938 there were so few boats that they could not have had any appreciable effect on shipping. If war with England had resulted, they would have operated only against her naval forces, particularly by minelaying off the British naval ports. But in 1939 the Supreme Command's directive for Fall Weiss stipulated that the first U-boat operations should be against enemy shipping.
    Even at that date there were still too few boats to obtain effective results against shipping. The question again arose as to whether in the interest of German surface ship operations it would not pay to use the U-boats against British naval forces. S.O. U-boats answered this question as follows (7) :‑
    " Results against the enemy's warships are only possible if these can be lured from their bases. Our weak surface forces cannot be relied upon to achieve this. The German Air Force could raid Scapa and perhaps succeed in driving the main force of the British Fleet (reported to be there) to the open sea. But at present air attacks are not permitted (Section 55).
    " In general, U-boat operations against naval forces promise little hope of success. On the surface the U-boat has no margin of speed to haul ahead for attack ; enemy escorting aircraft could generally forestall such action. The low underwater speed of the U-boat does not permit attack on fast warships except when the boat is directly in the path of the enemy, and that happens very seldom."
    The prospects of success in support of our own surface forces' operations were generally not encouraging, and so the Naval Staff decided on 7th September that the few ocean-going boats were to operate against shipping.

    Operational Distribution

    At this time all the 22 boats available for Atlantic operations were at sea, with none in reserve. This high figure would not be reached again within the next few months ; probably not even within the next year, for the reduction through losses and damage, and the necessary recall of boats for training, could not be compensated by the new boats, which were being commissioned at the rate of about two a month. The problem arose as to whether it would be more advantageous to distribute the boats equally over the operational area or to concentrate them temporarily in certain regions. If the boats were distributed equally, about one third of the 22 could be sent to the Atlantic at one time. In other words, the Atlantic boats would spend one third of their time refitting, one third proceeding to and from the operational area, and the remainder in that area. Six to eight boats could normally obtain only chance successes ; if these boats operated singly, results would be achieved only until Atlantic shipping could be organised into convoys.
    " While there are so few boats in the operational area it seems advisable to concentrate them with a view to gaining one major success, such as the destruction of a whole convoy " (8).
    At that time nobody could prophesy how the operational situation would develop. The number of boats ready for operations would vary according to the dockyard periods, nature of repairs, special duties, and the health of the crews. Any planned concentration against shipping would only be possible by retaining boats in port prior to the operation. This would necessarily involve a period of inactivity for some boats, with immunity to shipping. Further loss of operational time would occur when the boats returned to base. The simultaneous arrival of many boats in the overburdened dockyards would prolong the refit and delay the next operation. Thus concenXtrated operations could only be justified if they showed a high degree of success.
    U-boat operations can follow no clear-cut mathematical formula. They depend on various factors, such as the weather, visibility, enemy traffic, and enemy defences. Every planned concenXtration of U-boats must involve an element of risk. But in view of the inevitable variations in numerical strength it seemed right to build up " U-boat waves " for concentrated disposition, by holding back single boats as necessary.
    If, however, the strategic objective necessitated the use of a very strong " U-boat wave ", then the orders would have to be issued in plenty of time and the interim drop in shipping losses would have to be accepted.

    Mine or Torpedo ?

    In the ground mine the Navy possessed an extremely effective weapon. According to the German specialists, the enemy would for some time be unable to counter it. For this reason it should be laid suddenly on a large scale, before the enemy had a chance to learn how to deal with it (9).
    The mine could be laid in depths up to 25-30 metres ; therefore only in coastal waters. It could be used in narrow approach channels, off the entrances to harbours, against shipping or naval forces—where U-boats could not remain long enough for torpedo operations, because of the strong patrols and the difficulties of navigation. The mines could be laid undetected in one quick sortie, and as shipping had to be confined to set channels, results seemed certain. With luck the harbours could even be blocked. There would be no point in laying the mines against shipping along the coast until it could be learned by careful observation what navigational restrictions had been imposed on coastal traffic.
    It would be appropriate to increase minelaying activity in winter, when the long nights and unfavourable weather prejudiced the torpedo-carrying U-boats' chances, and when boats with a small radius of action could not be sure of expending their torpedoes before having to return for fuel. In all minelaying operations it was considered that the boats should also carry a limited number of torpedoes in case of a favourable target. In short, they should combine minelaying with torpedo attacks. But the general principle, even with coastal operations, was that the torpedo remained the main weapon of the U-boat, while mining operations would be ordered from time to time, as occasion arose (10).

    The Prize Regulations

    The German Admiralty's general directive to U-boats was to operate against enemy shipping, while conforming to the terms of the new Prize Regulations. It should here be explained that each U-boat always carried a copy of these Regulations, which laid down the conditions under which shipping could be attacked, and the exact procedure to be adopted in wartime against various categories of ships. These practical instructions for the use of U-boat commanders had only recently been drafted, and were based on the international regulations agreed upon in 1930 by the principal maritime powers, to which Germany had also become a party in 1936

    Baltic Operations

    The Navy's task was to cut off the Polish Naval forces, to control merchant shipping, to carry out unobtrusive reconnaissance and to prevent enemy forces from penetrating into the Baltic and the Kattegat. The U-boats had little prospect of action against the few Polish ships.
    The operational plans were drawn up by the Naval Staff in conjunction with Naval Group East. They did not altogether meet the views of S.O. U-boats, who, although agreeing to reconnaissance in the northern Baltic, thought that U-boats off the Gulf of Danzig were not needed against the insignificant Polish naval forces.
    The following were the individual tasks :‑
    minelaying with three boats (Type VII) off Hela Peninsula to block the route from the Hela Coast against outward bound Polish forces.
    continuous patrol off Hela by these boats on completion of the minelaying operation ;
    reconnaissance to locate Polish naval forces including minelayers and minesweepers ;
    reconnaissance patrols in the Baltic by fourteen boats of Type II and Type VII ; the areas included the Gulf of Finland, the Irben Strait, Gotland, and Kattegat, in conjunction with aircraft (11).
    Should Russian aggression result from our operations against Poland, a redisposition of U-boats in the Baltic was planned, and all boats carried a sealed operational order against this eventuality. It ordered a concentration in the immediate vicinity of the Gulf of Finland.
    The Emergency Period

    By the middle of August all the U-boats detailed for the above operations were ready. They had either completed their dockyard periods or were in the Baltic on manoeuvres with their flotillas. The large U-boats, intended for the Atlantic, prepared for war, while in the Baltic similar orders were received as follows :‑
    on 19th August : by all boats of the Third and Fifth U-boat Flotillas, which were to patrol off the Gulf of Finland, Gotland and Irben Strait ;
    on 21st August : by the three U-boats of the Second U-boat Flotilla (Type VII), which were to operate off Hela (minelaying and patrol) ;
    on 22nd August : by the three U-boats from the U-boat School, which were to patrol the Kattegat.
    The boats were to assemble in Mecklenburg Bight and Rugen.
    Not all of these measures were carried into effect. The slackening of the tension in the Baltic —the result of the Non-Aggression Pact with Russia—caused the cancellation on 23rd August of the reconnaissance patrols in the Gulf of Finland and the Gotland area, though one boat was left there. Seven Type II boats were transferred to the North Sea under the command of S.O. U-boats West, leaving only ten operational boats in the Baltic. On receipt of the order to prepare for Fall Weiss, these left for their assembly areas early on 24th August.
    The original plans provided for an attack on Poland 48 hours after the assembly order. The treaty concluded between Britain and Poland altered the situation, and on the evening of 25th August the Fiihrer postponed the starting date, which was to have been at 0430 on 26th August. As a result, the boats were ordered to return to port, excepting two off Irben Strait and Libau, but as the tension persisted, they were sent back to their waiting positions after replenishing. On 30th August U.31, in her waiting position north of Hela, was the first to sight the three Polish destroyers on their way to Britain. They were later spotted several times by aircraft and surface forces, and were last reported by U.6 (Kattegat patrol) leaving the Kattegat on the morning of 31st August.
    With the escape of the destroyers—the one valuable element of the Polish Navy—the intended German minelaying operations off Hela became redundant, and the Naval Staff on 31st August ordered the three 500-ton U-boats concerned to be released for operations in the Atlantic. At the same time, Commodore Donitz turned over the command of U-boats in the Baltic to ComXmander Schomburg, and himself assumed command in Wilhelmshaven, as S.O. U-boats West.

    Course of Events after the Outbreak of War

    When the war against Poland began on 1st September, 1939, the seven U-boats (Type II) then in the Baltic were disposed as follows :—two off the Gulf of Danzig, three near LdsO patrolling the Kattegat, one outside the Irben Strait and one off Libau. The last two were recalled on the following day to provide relief for the other groups.
    Until 7th September there were always two or three boats off the Gulf of Danzig. They lay submerged during the day, ready to attack any Polish submarines which might appear. At night withdrew northwards to the open sea. Polish submarines were sighted several times ; the an boats fired a torpedo on 3rd and again on 7th September, and the commanders reported that in each case a submarine had been destroyed. When the actual positions of the Polish sub-es were later established, it was evident that in both cases the German commanders had been ken. What they had in the darkness taken to be a hit had been a premature explosion due lure of the magnetic pistol. These were the first of a series of torpedo failures which were to handicap U-boat operations for many months.
    On 7th September the boats patrolling the Gulf of Danzig were transferred to S.O. U-boats for operations in the North Sea.
    Patrol of the Kattegat from the Laso area was carried out by two to three boats. Two further were placed, one at the north end of the Sound and one at the northern approaches to the
    On 10th September all patrols were canceled, and the boats were released for operations North Sea or for training purposes with the U-boat School.
    As anticipated, the U-boat operations against Poland ended without any major incidents. Baltic was free of enemy naval forces and in the years that followed was used as a U-boat training ground.
    James S likes this.
  2. James S

    James S Very Senior Member

    Peter, Gunther Hessler's post war study which he was asked to write for the Admiralty a three volume history with a supporting set of 7 or 8 large maps and diagrams for each volume.

    The switch from the Baltic to GB on the negotiation of the pact with Stalin is an interesting and not often reported action.

    Hessler's account was written without any knowledge of Ultra / Enigma and is very much the war as "we saw it", no enlightenment from the Allies or input into the study.

    Published by HMSO books in the late 1980's it is a very useful study but i some instances more recent information has over taken it and should be taken into account but it is a very good research tool. :)
  3. Peter Clare

    Peter Clare Very Senior Member

    U-boat activity 24 May - 31 May 1941 / Bismarck

    On the morning of 24th May, 1941, Bismarck—(with the Commander-in-Chief, Fleet)—and Prinz Eugen attempted to break through via Denmark Strait, where they encountered and sank H.M.S. Hood. No direct co-operation had been planned between the U-boats and the surface ships. On 8th April the Commander-in-Chief, Fleet had met F.O. U-boats in Paris, when they discussed the possibilities of U-boat support for the battleship operation. It was decided that the boats were to be disposed according to the normal requirements of U-boat warfare, and that any opportunities of co-operation with the surface ships were to be fully exploited. An experienced U-boat officer was embarked in Bismarck, and the flagship kept watch on the U-boat wave so as to know the boats' positions and the intentions of F.O. U-boats (70).
    The western group of U-boats was only a hundred or two miles from Bismarck. Independent action by F.O. U-boats to bring them nearer was pointless until the Commander-in-Chief's plans were known. But on this occasion Dönitz suspended operations against shipping and placed all available boats unreservedly at the disposal of Admiral Saalwdchter, Commander of Naval Group West, who was in control of German surface ship operations in the Atlantic.
    On 24th May the Commander-in-Chief, Fleet requested the western U-boat group to assemble in a narrow patrol line 60 miles broad and 280 miles south of Cape Farewell (northwest–southeast patrol line, Diagram 11, Point 5). He intended to lure his persistent shadowers across this line on the morning of 25th May. But the patrol line was cancelled on the evening of 24th May when it was learned that the Commander-in-Chief had changed his plans. It seemed that Bismarck was returning to St. Nazaire, while Prinz Eugen would proceed independently to the southwest. On the order of Naval Group West the boats proceeded to a new patrol line 240 miles wide and 300 miles southeast of Cape Farewell (Point 6).
    The assumption that Bismarck would return to St. Nazaire gained in probability when on the night of 24th/25th May it was learned that she had been torpedoed by carrier-borne aircraft. The primary task now was to protect the returning ship. Group West ordered the western U-boat group to proceed eastwards at 12 knots to intercept heavy units pursuing Bismarck. The speed of the surface forces, the slowness of the U-boats and the uncertainty as to Bismarck's position and intentions made contact problematical. When in the evening it could be assumed that Bismarck and her pursuers had left that area, the boats were ordered to return to their former positions. They had insufficient speed for the southeasterly pursuit.
    The second measure was the attempt to help the damaged ship in the Bay of Biscay. In anticipation of her return, all homeward and outward bound boats had been ordered on 24th May to assemble in an area 450 miles west of St. Nazaire, in latitude 47° 20' North, between 12° and 15° West. There were six boats in all, U.48, U.73, U.74, U,97, U.98 and U.556. Three of these could be used only for reconnaissance. In the forenoon of 25th May all were ordered to form a northwest–southeast patrol line towards Cape Ortegal (Point 7). If Bismarck were steering a southeasterly course, she would be able to draw her pursuers and shadowers across this formation. Apart from its reconnaissance value, the disposition would be practically useless against enemy ships coming from the north or south. But a heavy storm prevented the boats from reaching their positions until 26th May.
    As expected, Bismarck approached the northwest flank of the patrol line. At 1844 on 26th May she reported her position and course of 115°, which meant that she would proceed parallel to and slightly east of the patrol line. At 2010 U.556 reported that Bismarck's pursuers were hot on her heels. This U-boat under her outstanding commander, Lt. Wohlfahrt, was without torpedoes. Shortage of fuel had prevented her from taking up position as the second boat from the northern end of the patrol line, and she was still 80 miles further north. Lt. Wohlfahrt commented in his War Diary :—

    "26th May, 1941 :—
    Position : 640 miles west of Land's End. Wind : northwest, force 6-7, sea 5 ; weather clear, partly overcast ; visibility moderate to good.
    1531 Submerged because of aircraft. Heard several explosions like gunfire.
    1948 Alarm. A battleship of King George class and an aircraft carrier, probably Ark Royal, suddenly sighted astern emerging from the mist at high speed. Inclination 170° right. If only I had torpedoes now ! I should not even have to approach, as I am in exactly the right position for firing. No destroyers and no zig-zagging ! I could get between them and finish them both off. The carrier has torpedo-bombers on board. I might have been able to help Bismarck.
    2039 Surfaced. Sent signal : ' Enemy sighted : one battleship, one aircraft carrier, course 115°, high speed in 48° 20' North 16° 20' West. Up to 2206 sent further signals on loss of contact, giving hydrophone bearings. I shall use the last of my fuel in an attempt to pursue them. Dive to listen, report hydrophone bearings and send homing signals.' . . ."
    Bismarck was unable to proceed along the patrol line as intended. She encountered torpedo-bombers, and at 2100 gave her position as 47° 20' North 14° 50' West, that is, 80 miles east of the left flank of the patrol line. The ship was out of control. At 2142 a radio message of top priority ordered all boats with torpedoes to proceed directly towards her at maximum speed, but heavy weather prevented this. The boats battled against a sea of force 6 in their attempt to find her. U.73, which had torpedoes, made temporary contact with enemy forces between 0000 and 0230 on 27th May, but lost it in the squalls, despite the flashes of heavy guns. Only U.556 managed to remain in the vicinity for a few hours :—

    "26th May, 1941
    :Position : 420 miles west of Brest.
    2330 Alarm. Destroyer suddenly approaching out of the mist. I am at 30 metres when she passes above. We can hear her screws. A narrow escape. No depth charges.

    27th May
    0000 Northwest wind, force 5 ; sea 5, rain squalls, moderate visibility, very dark. Surfaced. What can I do for Bismarck ? I can see her starshells and gun flashes. Sudden bursts of gunfire. It is an awful feeling to be so near, yet unable to help. I can only continue to reconnoiter and guide the U-boats that still have torpedoes. I maintain contact at the limit If visual range, report position and send homing signals to bring the other boats up.1352 I proceed southwards on the eastern side. Fuel shortage will soon force me to return.
    0400 Sea is increasing constantly. Bismarck is still fighting. Reported weather for aircraft Ind at 0630 sent my last shadowing report. Sighted U.74 and turned over to her by visual signal the duty of shadowing. I can still remain here by using my motors at dead slow. If I use Diesels, I will run out of fuel. . . ."
    The pitching boats could not take accurate bearings on the homing signals sent during the t by U.556 and Bismarck, and they were thus deprived of their only means of finding her, he position she gave at 2100 was much further southeast than her true position. Even if the Dats had reached her, it is doubtful whether in the prevailing weather they could have been ul.
    About 0700 on 27th May, 1941, the Commander-in-Chief requested that a U-boat be sent to fetch his War Diary. Lt. Wohlfahrt was detailed, but did not receive the order until 1000 as ny aircraft had forced him to submerge. Bismarck sank at about this time. The boats carefully searched the area up to 31st May, but picked up only three survivors.
  4. James S

    James S Very Senior Member

    Also from "The U Boat war 1939-1945" (HMSO).
    Chapter III- The Atlantic and The Mediterranean . (May- December1941).
    Failure To Intercept

    124. Own radio under Suspicion.
    When, at the end of April 1941, F.O.U-boats informed the Naval Staff of his decision to dispose the U-boats further west, he ventured the opinion that the few convoy sightings in April were due not only to inherent fcators such as the dispersion of routes in a vast area and the few U-boats, but also to a temporary reduction in or stoppage of enemy traffic. The Naval Staff's investigations did not bear this out. Neither the information gained by the Radio Intercept Service nor any other clues indicated a drop in traffic. Britain had to maintain a steady stream of imports, which could not be stopped or reduced for long, no matter how high her shipping losses might be.It was more likely that convoys might be systematically by-passing U-boat formations.
    The Naval Staff investigated this possibility and concluded that radio transmissions by the boats had enabled the enemy to locate and avoid them. Analysing our own radio traffic, it seemed that the convoy SC2 could have evaded us at the end of April. It was therefore decided to restrict the use of radio as far as possible. At the same time, radio deception was to be employed and a Radio Intelligence officer at the headquarters of F.O. U-boats was to make a comprehensive evaluation the enemy situation. This decision again raised in an acute form the question of the advantages and perils of radio in controlled operations.

    125. Dangers of Location by D/F.
    It had been known in peace-time that the Royal Navy had always devoted much attention to its D/F and location service. With stations from Land's End to the Shetlands, the base provided angles of interception adequate for the fixing all traffic east of the 35th meridian. If British D/F stations were set up in Iceland, Greenland, Newfoundland, Spain and the Azores, this would allow fixes to be obtained by cross bearing in the whole of the North Atlantic. It was certain that a D/F station in Iceland had been working for the British from 21st April, 1941 and further developments could be expected.
    When Brest was occupied, the French Admiralty's radio messages were found almost intact including the collection of short wave radio bearings taken on U-boats by British and French D/F stations. When the British submarine "HMS Seal" was captured in May 1940 , an examination of her radio messages showed that during the Norwegian campaign the British Admiralty had several times supplied warships with short-wave bearings of U-boats and that British submarines had orders to maintain the strictest radio silence, because of the danger of being located.
    In the first few months of the war careful examination of the enemy's use of D/F and his countermeasures had given no cause for alarm. The U-boat Commanders reported that the enemy certainly obtained fixes on the boats. But his D/F system did not appear to be very accurate, according to the war diary for 23rd January , 1940:-

    ".....As far as can be ascertained, the enemy's errors in fixing by direction finding vary with the range from his coast. At 300 miles an average an average error is 60-80 miles. Hitherto the best fix, immediately off the west coast of France, was 30 miles out. The worst error amounted to 320 miles at a range of 600 miles...."

    The enemy rapidly improved his technique, for after the middle of 1940 the few instances of enemy direction finding picked up by our Radio Intercept Service were much more accurate. In October U-47 and other meteorological boats reported that even up to longitudes of 25 degree West they were almost always pursued by enemy forces within one or two hours of making short signal weather reports. Our countermeasures - greater radio discipline, changing of frequencies and extensive adoption of "short signals" procedure - seemed unavailing against the efficient British D/F technique. We had to assume that all our radio messages and short signals would be fixed and probably exploited.

    126. Possible Enemy Sources of Intelligence.
    Measures were taken to ascertain whether the enemy's diversion of traffic was the direct result of his own Radio Intelligence. The Naval Staff appointed a Radio Intelligence officer to the Staff of F.O. U-boats. In the past, insufficient attention had been paid to this subject by the U-boat Command. Now all available details of naval and merchant traffic collected from the U-boat reports, air reconnaissance, German Signals Intelligence, agents , metrological trawlers and other German and Italian units were entered on a large map. The map also showed all information the enemy could possibly possess on U-boat positions derived from torpedoed ships, SSS reports,U-boat warning reports, sighting reports made by aircraft, and U-boat radio messages, including short signals - presuming these to have been fixed by D/F. It was assumed that the enemy knew the exact number of boats leaving Germany and French ports.

    To check the accuracy of Bristih D/F, the U-boats position reports were taken from their War Diaries on their return, and compared with the decrypted British transmission of D/F bearings. All additional information on convoy routes from subsequently decrypted signals and other sources was entered into the evaluation maps. Independently and on a much larger scale, specialists of the main radio Intelligence Centre at the German Admiralty also evaluated the enemy situation. F.O. U-boats utilised their analyses in conjunction with the U-boat commanders reports.

    On 7th June1941, , a comparison between the investigations by F.O. U-boats and those of the Radio Intelligence Centre seemed to show that the enemy reactions had not been the result of the boats' use of radio, but were due to sightings, attacks by U-boats and navigational and tactical data. It was shown that despite radio transmission by the boats and sinkings and convoy battles in the area under examination, the enemy had often continued to run his single ships or convoys through the area. It was not clear why the British Commander- in Chief Western Approaches, who was in charge of the routing, followed this procedure.

    The following conclusions were drawn :-
    The enemy obtained fairly accurate fixes of all our radio transmissions ;
    every use of radio helped to complete the enemy's picture of the situation and might lead to by-passing boats. ;
    the investigation failed to discover whether and how the enemy reacted, and this uncertainty would continue.

    127. Control of Radio Traffic.
    F.O. U-boats now devised methods which would eliminate the less important radio messages.
    The principles were given in standing order No. 243 of 9th June 1941. :-
    "In the attack area : radio is to be used only for messages of tactical importance or on request from the Command, or if the enemy is already aware of the boats positions.

    On passage: As above. Occasional transmission of less important information may be made if it is certain that succeeding boats or those already in the area concerned will not be endangered.

    Technical : Wavelengths are not to be changed frequently; additional channels to be introduced ; new radio procedure to make it difficult for the enemy to take bearings."

    These instructions did not result in any marked reduction in the use of radio, for passing of messages of tactical importance" still involved frequent transmission.

    128. Radio Detection.
    Since it was found impossible to reduce the radio traffic substantially without sacrificing sinkings, measures had to be adopted - such as synchronisation or seperation of the time and areas for transmission of messages - to make it harder for the enemy to deduce the true situation. Indispensable transmission included the following : entering and leaving Biscay, commencement of homeward journey, weather, fuel remaining. The naval Staff's proposal to use radio deception evoked this comment from F.O. U-boats :-

    "....the employment of radio deception for the purpose of simulating that certain areas are occupied and others unoccupied by U-boats seems admirable in theory but in practice it is extremely complicated. The experts on the problem are faced with the difficulty of following the thought process of the enemy. There is also the danger of inaccurate D/F bearings by the enemy which might defeat the purpose of the scheme...."

    However small - scale deception schemes were carried out. On 29th June, 1941, several homeward bound boats were ordered to transmit while south west of Ireland in order to dissuade a convoy, sighted by the Luftwaffe 300 miles west of Ireland, from evading to the south.

    With many more U-boats at sea it would perhaps be possible, by means of carefully planned transmissions schedules from all boats- whether on passage or on operations - to give the Command a complete picture of the situation while at the same time confusing the enemy as to the true location of the attacking formations. But this idea was never put into practice, and F.O U-boats had to base his decisions on the few radio messages that boats could safely send. This handicapped operational control, particularly in 1941, when there was so little help from air reconnaissance.

    129. Question of the betrayal of U-Boat Positions.

    During investigations early in 1941 on certain minor operational failures, a suspicion arose that the enemy had further unknown sources of information on U-boat dispositions. This suspicion was first mentioned in the War Diary on 18th April 1941.

    "outside her attack area, U-94 at times encountered heavy north -south traffic about 240 miles east of Greenland. U-101 had a similar experience in the same locality, also outside her attack area. These observations give the impression that British traffic had been diverted around our attacking formations because the enemy had learned of their location from an unknown source. This might explain the failure of the convoy operation in co-operation with the Luftwaffe on 4th March. The convoy should have been intercepted that day by a reconnaissance line of U-boats and on 5th March by a patrol line. It was first reported steering a westerly course. After the first reconnaissance line had been directed into position, the convoy deviated far to the north, thus avoiding the second patrol line which would otherwise have been in a favourable position to attack.

    "Although much of this is conjecture, every possibility of security leakage must be obviated at all costs. Within the U-boat service I have ordered that as few people should have knowledge of U-boat operations. For the same reason I have cancelled the daily position reports to Group West, Air Commander Atlantic, and Liaison Officer, Bordeaux. Outside the U-boat service, Commander in Chief navy has restricted to the minimum the stations which may tune to the U-boat wavelength, thus eliminating unauthorised use. All offices which may tune to the U-boat wavelength, thus eliminating unauthorised use.All offices which, for operational or technical reasons , must use the U-boat wavelength have been informed of this suspected leakage of information and have been ordered to preserve absolute secrecy and severely restrict the number of persons who have access. the Commander in -Chief-Navy has also approved my request for the introduction of a special cypher for U-boats"

    This cypher introduced in the summer of 1941 - prevented unauthorised persons from knowing about the operations. It was supplied only to offices concerned with U-boat communications. Under the new arrangements the Fliegerfuhrer Atlantic and the liaison officer with the Italians at Bordeaux received only occasional reviews of the U-boat situation, while Naval group West no longer received signals by land-line, but tuned in to the radio frequencies used by U-boats.

    the danger of leakage was greater in German Admiralty. Up to May 1941, the practice here had been to make copies of the plotting room chart of dispositions, which were available to a small number of officers. The dispositions were send daily by teleprinter to the German Admiral in the Balkans and to the German Naval Command in Italy, though there was no real reason why they should have this information. This practice was perhaps typical of the German inclination to pass secrets to other authorities, which may have well have been accessible to enemy agents at some point along the route. Whereas F.O. U-boats had already restricted access in his own service, he had been unaware until now of this wider distribution to outside authorities.

    A further step towards security was taken on 9th September, 1941 when it was decided to encode the naval grid squares, before passing the en clair texts to the cypher office. using a bigram code which was changed at irregular intervals, all grid squares in the North Atlantic were encoded. The system was not infallible, but served the purpose of concealing the actual positions of U-boats from communication personnel and others who were not allowed access to the map room.
    (Further mention of security problems will be made when covering the years 1942-1944.)

    My note.
    (To some extent increased security provided a cover for the degree to which the Enigma had been compromised and it would seem the importance of the fourth rotor was not fully realised. parallels with the torpedo crisis - Donitz had asked if it was possible for Enigma to have been broken and he was told no , he had been previously reassured that the torpedoes were fine that it was the use and maintenance at the front which was largely at fault for failures ).
  5. Oldman

    Oldman Very Senior Member

    Thanks for the post I know liitle about the U Boat War at all so it filled a gap and I will have to make a point of reading about it.

    my limited knowledge on the subject goes back to a sailor I worked with who said all I was told was when the Uboats start going for the escorts the you know you are winning

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