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Introduction

The Royal Navy's Operation Deadlight, which was the executive action which led to the sinking of 116 German U-Boats off Northern Ireland between 27 November 1945 and 12 February 1946, was the culmination of the long-held determination of the British Government to ensure the total elimination of the German Navy’s submarine fleet after the end of WW2.

UK Planning for German Naval Disarmament

UK planning for the end of the war assumed that Britain would occupy the north west zone of Germany, and that the Royal Navy would be responsible for the main German naval bases. Thus, at the cessation of hostilities, all German U-Boats would immediately be moved to the UK prior to Allied agreement about their destruction.

The Royal Navy therefore pressed ahead in the first half of 1944 with the detailed planning for the post-war transfer of all remaining German U-Boats to British ports. It was intended that the U-Boats would be moved to the naval port at Lisahally in Northern Ireland, and to the naval anchorage in Loch Ryan in south-west Scotland. The proposed transfer arrangements were code-named Operation Pledge.

Operation Pledge

On 4 May 1945 the German Navy had ordered all U-Boats to cease operations and return to Norwegian ports. This was superseded on 8 May when the Admiralty ordered all U-Boats to surrender, and for those at sea to head for designated reception ports; the prime one of which was Loch Eriboll in north west Scotland. As a result, 156 U-Boats surrendered on both sides of the Atlantic.

To implement Operation Pledge it was necessary to organise suitable reception arrangements in Loch Eriboll, and the naval units which comprised the Loch Eriboll Force arrived there on 9 May. The first U-Boat to surrender arrived on 10 May and, between then and 18 May, a further 17 surrendered in Loch Eriboll. However, none of these U-Boats spent long at Loch Eriboll. Instead, they were moved quickly to Loch Alsh on the west coast of Scotland where the majority of the German crews were taken into captivity, and from there they were moved to Lisahally to await final disposal.

On 19 May, a group of 15 U-Boats arrived from Norway. This group had been in transit to Trondheim from Narvik, where they had surrendered, when it was intercepted in Vestfiord on 17 May and diverted to Loch Eriboll. Once these 15 U-Boats had been processed, the Operation Pledge reception organisation was moved from Loch Eriboll to Scapa Flow in the Orkney Islands on 28 May in order to process the remaining U-Boats that had surrendered in Norwegian ports.

The first group of 12 U-Boats from Norway arrived at Scapa Flow on 30 May and were then sent directly to either Lisahally or Loch Ryan. Between then and 5 June, when the Operation Pledge reception force was disbanded, a further 52 U-Boats arrived at Scapa Flow, from where they were moved to either Lisahally or Loch Ryan.

There were still 35 seaworthy surrendered U-Boats in Norwegian and German ports. In the latter case, most were located at Wilhelmshaven, having been transferred there from the Danish and other German ports where they had surrendered in early May. These U-Boats were transferred to either Lisahally or Loch Ryan between 3 June and 30 June. Similarly, the U-Boat that had been interned in Spain since September 1943 (U-760), the two that had surrendered from sea in Gibraltar, and the three that had surrendered from sea in Portland in the south of England were transferred to one or other of the two anchorages.

This left just 10 surrendered U-Boats remaining in continental ports, all of which were unseaworthy for transfer: one in France, two in Germany and seven in Norway. The two in Germany were the two U-Boats which had surrendered in Cuxhaven on 5 May (U-1406 and U-1407), but which had then been scuttled on 7 May. These were then raised on 1 June and taken to Kiel to await decisions about their ultimate disposal.

Thus, of the 156 U-Boats that had surrendered either from sea or in ports at the end of the European War (plus the one that had been interned in Spain), 138 were transferred to Lisahally and Loch Ryan to await decisions on their final disposal. Of the remainder, nine had surrendered from sea in Canada, the USA and Argentina, and 10 were unseaworthy in European ports.

Allied Planning for the Division and Destruction of Surviving U-Boats

After the surrender in May 1945, political discussions continued between the Allies concerning the final disposal of the surviving German naval vessels, the result of which was an agreement to the retain just 30 U-Boats in total, to be divided equally between the UK, the USA and the USSR. The result of these discussions was the publication of the "Proceedings" (Minutes) of the Potsdam Heads of State Conference which took place in Berlin between 17 July and 2 August 1945. In respect of the remaining U-Boats, the Proceedings concluded that:

The larger part of the German submarine fleet shall be sunk. Not more than thirty submarines shall be preserved and divided equally between the USSR, UK and USA for experimental and technical purposes.

It was also stated that:

The Three Governments agree to constitute a Tripartite Naval Commission to submit agreed recommendations to the Three Governments for the allocation of specific German warships and that The Three Governments agreed that transfers shall be completed as soon as possible, but not later than 15 February 1946.

The Tripartite Naval Commission

The task of the Tripartite Naval Commission, which began its work on 15 August 1945, was to select the 30 U-Boats that were to be retained by the three Allies. It was therefore required to review the 135 U-Boats moored in Loch Ryan and at Lisahally (by then one had been returned to Holland, and two Type XX1 U-Boats had been moved to the USA in August), as well as the then 11 U-Boats in the USA, including the five that had surrendered in America, the two that had surrendered in Canada and the two that had surrendered in Argentina. Also included in the review were two Type XVIIB U-Boats (U-1406 and U-1407) which had been raised after surrendering in Cuxhaven on 5 May and then being scuttled on 7 May.

On 10 October, at its 13th Meeting, the Commission formally agreed details of the 30 U-Boats which were to be allocated to each of the UK, the USA and the USSR, but deferred a decision about the fate of the unallocated submarines. This was taken at the 18th Meeting of the Commission on 29 October, when it was agreed that all unallocated submarines were to be sunk in the open sea in a depth of not less than one hundred metres by not later that 15 February 1946.

Thus, of the 135 U-Boats moored in Loch Ryan and at Lisahally, eight were allocated to the UK, one to the USA and 10 to the USSR. This left 116 U-Boats at Lisahally and in Loch Ryan awaiting final disposal by the Royal Navy. This therefore led to Operation Deadlight.

Operation Deadlight

As the remaining 116 U-Boats were to be sunk at sea, it was decided that the disposal action should be initiated without delay. This was not only to meet the deadline of 15 February 1946, but also because the imminent onset of winter and its associated rough seas in the area to the north west of Loch Ryan and Lough Foyle would make the towing and scuttling of the U-Boats a hazardous task. As a result, Operation Deadlight was initiated immediately after the Tripartite Naval Commission’s 18th Meeting on 29 October.

On 31 October, the Admiralty instructed the RN Commander-in-Chief at Rosyth to begin making the detailed arrangements for the disposal of the unallocated U-Boats. With the aim of completing the exercise as soon as possible, the initial planning meeting to determine the necessary actions was held at Pitraevie in Fife on 5 November, and the formal order for Operation Deadlight was issued on 14 November; it being defined as a plan for scuttling 110 U-Boats from Loch Ryan (86) and Lisahally(24) in deep water off the north west coast of Ireland, starting on 25 November.

The omission of six U-Boats from the list in Annex A of the Deadlight Operation Order has caused considerable confusion ever since, despite the UK’s 1946 Naval Estimates (Cmd 7054) giving the correct figure of 116.

The six U-Boats missing from Annex A, which were all moored at Lisahally, were U-975, U-1023, U-2351, U-2356, U-2502 and U-3514 and, in each case, there were ongoing discussions about their possible inclusion in the lists of those U-Boats to be allocated to the Allies. It had been agreed by the Tripartite Naval Commission that there should be a degree of flexibility and that bi-lateral exchanges of individual ships and craft between the Allies could be made as desired. Thus, there are a number of differences between the original lists of the U-Boats allocated to each of the three Allies and those that were finally implemented. Because these six U-Boats were all included in the initial allocation lists, they were therefore omitted from Annex A. However, ultimately they did not feature in the final allocations, and were therefore added to the original list of 110 unallocated U-Boats after the Deadlight Operation Order was published.

Of the 116 U-Boats, 86 were moored in Loch Ryan and 30 were tied up to pontoons at Lisahally, and they comprised 1 type IID, 73 type VIICs, 1 type VIID, 1 type VIIF, 11 type IXCs, 4 type IXD2s, 4 type XXIs and 18 type XXIIIs. The individual U-Boats which were sunk during Operation Deadlight were:

Ex-Loch Ryan (86)

U-143, U-145, U-149, U-150, U-155, U-170, U-218, U-245, U-249, U-255, U-281, U-291, U-293, U-295, U-298, U-299, U-312, U-313, U-318, U-328, U-368, U-369, U-427, U-481, U-483, U-485, U-532, U-539, U-637, U-680, U-716, U-720, U-739, U-760, U-773, U-775, U-776, U-778, U-779, U-806, U-826, U-868, U-907, U-928, U-956, U-968, U-978, U-991, U-992, U-994, U-997, U-1002, U-1004, U-1005, U-1009, U-1019, U-1052, U-1061, U-1102, U-1103, U-1104, U-1110, U-1163, U-1194, U-1198, U-1203, U-1230, U-1233, U-1271, U-1272, U-1301, U-1307, U-2321, U-2322, U-2324, U-2325, U-2328, U-2329, U-2334, U-2335, U-2337, U-2345, U-2350, U-2354, U-2361 and U-2363.

Ex-Lisahally (30)

U-244, U-278, U-294, U-363, U-516, U-541, U-668, U-764, U-802, U-825, U-861, U-874, U-875, U-883, U-901, U-930, U-975, U-1010, U-1022, U-1023, U-1109, U-1165, U-2336, U-2341, U-2351, U-2356, U-2502, U-2506, U-2511 and U-3514.

The aim of Operation Deadlight, as set out in the Operation Order on 14 November, was that all the U-Boats should be towed (unmanned) to a designated position 130 miles to the north west of Lough Foyle, which was 180 miles from Loch Ryan, where they would then be sunk. The prime method was to be by the use of demolition charges, however if weather conditions allowed, 36 were to be sunk by RAF and Fleet Air Arm aircraft, and others were to be sunk by RN submarines. If any of these methods of disposal failed, then the U-Boats were to be sunk by gunfire.

The plan was to dispose of the U-Boats from Loch Ryan first, and then to deal with those from Lisahally. It would take two days for the towed U-Boats to reach the designated scuttling area. So, though the first sailing from Loch Ryan took place on 25 November, the sinkings of the first five U-Boats (U-2322, U-2324, U-2328, U-2345 and U-2361) actually took place on 27 November.

As expected, the weather was particularly bad in November and December 1945, and the planned disposal arrangements did not work on the majority of occasions, especially as far as the plans for sinking the U-Boats with demolition charges were concerned. There were also major problems with the towing of the unmanned, unmaintained and, in many cases, almost unseaworthy U-Boats.

Comparison of the planned disposal arrangements with what actually happened shows the scale of disruption wrought by the weather. Only two of the U-Boats were sunk by demolition charges, only seven by submarines and only 13 by aircraft. Of the remainder, almost 50% foundered under tow before they ever reached the designated scuttling area. These either sank directly or were sunk by gunfire, some of them in positions very close to the entrances to Loch Ryan and Lough Foyle. The remainder were sunk by gunfire, as it was far too dangerous to follow the pre-planned demolition procedure.

There were three distinct phases to Operation Deadlight. The 86 U-Boats from Loch Ryan were sunk between 27 November and 30 December 1945, 28 of the U-Boats from Lisahally were sunk between 29 December 1945 and 9 January 1946, and the remaining two U-Boats from Lisahally (U-975 and U-3514), which were two of the late additions, were sunk on 10 and 12 February 1946 respectively. After that, the C-in-C Rosyth reported the completion of Operation Deadlight in two messages to the Admiralty. The sinking of 114 U-Boats was confirmed in his message 08 0934 Jan 46, and the sinking of the final two U-Boats was confirmed in his message 12 1156 Feb 46.

Finally, for completeness, and because they also came under the aegis of the Tripartite Naval Commission, and especially because they were all listed in the Commission's Final Report of 6 December 1945 as afloat, but unallocated submarines - to be sunk not later than 15 February 1946, mention needs to be made of 11 other U-Boats.

First, there were two unallocated U-Boats in the USA (U-805 and U-1228) which were sunk in February 1946. Second, there were two unallocated U-Boats in the US-administered Bremen enclave in north Germany which, rather than surrendering, had been captured in a de-commissioned state in May 1945 (U-1197 and U-1232), and these were both towed out into the North Sea and sunk by the US Navy in February 1946.

And, third, there were seven unallocated ex-U-Boats which had surrendered in the Far East under the Japanese flag at the end of the war with Japan in August 1945. These were U-181 and U-862 which had surrendered in Singapore, U-195 and U-219 which had surrendered in Java, and U-511, U-IT-24 and U-IT-25 which had surrendered in Japan. The first four, which were all under British jurisdiction were sunk in February 1946, but the three in Japan were not sunk until April 1946, after the US had successfully argued that they were Japanese submarines when they surrendered, and that their disposal was nothing to do with the Tripartite Naval Commission.

Conclusion

The sinking of the 116 U-Boats and the completion of Operation Deadlight on 12 February 1946 marked the end of virtually all of the Kriegsmarine's surviving serviceable U-Boats which had surrendered at the end of WW2 in Europe. The Allies had been allocated 30 for technical purposes, one had been returned to Holland (UD-5), two others (U-805 and U-1228) had been sunk off the west coast of the USA in early February 1946, and a further eight unseaworthy U-Boats remained in continental ports (one in France and seven in Norway). Thus, the long-held determination of the British Government to ensure the elimination of the German submarine fleet had been achieved.