U-Boats that Surrendered - Operation Cabal
The Delivery of 10 U-Boats from the UK to the USSR in 1945/46
by Derek Waller
The aim of Operation Cabal was the delivery by the Royal Navy of 10 surrendered German U-Boats from the naval port of Lisahally (HMS Ferret IV) in Lough Foyle in Northern Ireland to the Russian-controlled Baltic port of Libau in Latvia.
As part of the post-War Tripartite Naval Agreement it had been agreed between the Allies that whilst: “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, the UK and the USA for experimental and technical purposes”.
In late August and early September 1945 Russian officers from the UK Tripartite Naval Board inspected the 136 U-boats moored in Lough Foyle and in Loch Ryan in south west Scotland. As a result, it was decided that the 10 U-Boats to be transferred to the USSR would be:
U-1057 (Type VIIC), U-1058 (Type VIIC), U-1064 (Type VIIC/41), U-1231 (Type IXC/40), U-1305 (Type VIIC/41), U-2353 (Type XXIII), U-2529 (Type XXI), U-3035 (Type XXI), U-3041 (Type XXI) and U-3514 (Type XXI). However, U-3514 was later replaced by U-3515 (Type XXI).
Prior to the transfer, seven of the U-Boats were moored at Lisahally, and three (U-1057, U-1064 and U-2353) were moored in Loch Ryan. However, these three U-Boats were moved to Lough Foyle on 31 October.
The original intention of the Russians was that the 10 U-Boats should be fully serviceable and should sail to Libau under their own power. The U-Boats were to have RN crews, but there was to be one Russian naval officer on each as an observer.
In the event, only five of the U-Boats were deemed to be capable of proceeding the whole way under their own power, and it was decided to tow the remaining five.
The transfer, code named Operation Cabal, began on 24 November when nine of the U-Boats (less U-3515) sailed from Moville at the mouth of Lough Foyle.
The planned route was around the north of Scotland, then through the Pentland Firth between Scotland and the Orkney Islands. After that, it was across the North Sea to south Norway, then through the Skagerrak and Kattegat to Copenhagen, and finally to the south of Sweden and across the Baltic to Libau.
The five under power were U-1057, U-1058, U-1064, U-1305 and U-1231, and they were escorted by HMS Garth, HMS Eglinton and HMS Zetland. The four under tow were U-2353 (HMS Riou), U-2529 (HMS Zephyr), U-3035 (HMS Tremadoc Bay) and U-3041 (HMS Narborough).
On 23 November, when U-3514 was being prepared to leave for Libau, she collided with another U-Boat, damaging her steering and aft hydroplanes. It was then discovered that her stern was distorted, and that she could not be transferred (even under tow). The Russians therefore agreed that U-3515 should be transferred instead; thus accounting for the latter’s late sailing, which was delayed until 6 December.
The five U-Boats which sailed under their own power and with escorts had a relatively trouble-free journey to Libau. However, it was a different matter for those that were under tow. The four which set out on 24 November experienced considerable bad weather on route, including Force 10 gales, and all had problems with their towing gear. Indeed, only seven of the U-Boats (U-1057, U-1058, U-1064, U-1231, U-1305, U-2353 and U-2529) arrived at Libau on 4 December. The three remaining U-Boats (U-3041, U-3035 and U-3515) all suffered considerable delays due to a combination of poor weather, technical defects and towing problems.
U-3041 which was being towed by HMS Narborough encountered problems with the towing gear which necessitated a diversion to Rosyth on 26 November. It then developed steering and other defects in the North Sea off Norway. This necessitated a diversion to Kristiansand (S) on 29 November for repairs which took 5 days. After repairs, the transfer resumed on 5 December, and she arrived in Libau on 10 December.
Similarly, U-3035 which was being towed by HMS Tremadoc Bay, developed steering defects off the north of Scotland. This resulted in a jammed rudder, and also necessitated a diversion to Rosyth on 28 November. After repairs, the transfer resumed on 7 December, and she arrived in Libau on 14 December.
The transfer of U-3515, which had started late because of the problems with U-3514, was itself beset with problems. After leaving Lough Foyle on 6 December under tow by HMS Icarus, and after poor weather caused it to take shelter in the Orkney Islands, ongoing towing problems together with a number of defects caused a diversion into Rosyth where it arrived on 11 December. The pair sailed again on 12 December, but returned yet again on 14 December after the tow parted again in more poor weather.
After that, and as described by the CO of HMS Icarus in his voyage report, “Icarus and U-3515 then remained in Rosyth Dockyard waiting for a serious defect in the submarine to be made good, and subsequently for the weather to moderate until Saturday the 26th January”.
Additionally a series of “confusing” signal messages are referred to in the 10 January 1946 "Report of Proceedings of Operation Cabal" submitted by Captain P Q Roberts who commanded the transfer to the 10 U-Boats to Libau:
On 14 December C-in-C Rosyth reported that: “Icarus and U-3515 had again put back into Rosyth with defects on the submarine”.
On 15 December C-in-C Rosyth reported that: “there was a further delay to Icarus and U-3515”.
On 20 December Captain Roberts received a signal saying that Icarus and U-3515 were: “to sail at 1300 on that day”. This signal is not recorded in the signal log attached to HMS Icarus’ voyage report which, perhaps significantly, records no signals between 13 December and 31 January 1946.
The exact nature and cause of U-3515’s defects is unclear, but on 20 December the starboard main (electric) motor was found to be damaged. The Russian Embassy in London believed that this may have been caused by sabotage, and there was a protracted argument between the Embassy and the Admiralty about the problem. A final trial of the repaired motor took place on 23 January 1946 but, because of the bad weather, the departure of U-3515 from Rosyth, again under tow by HMS Icarus, was delayed until 26 January.
Thereafter, the remainder of the journey was uneventful, and U-3515 finally arrived in Libau on 2 February 1946, thereby completing Operation Cabal.
Specific Details of the 10 U-Boats Transferred to the USSR
U-1057 Surrendered on 10 May in Bergen, Norway. Transferred to Loch Ryan on 2 June. Transferred to Lough Foyle on 31 October prior to move to USSR. Sailed under own power with RN crew and escort on 24 November. Arrived Libau on 4 December.
U-1058 Surrendered from sea in Loch Eriboll, Scotland on 10 May. Transferred to Lough Foyle. Sailed under own power with RN crew and escort on 24 November. Arrived Libau on 4 December.
U-1064 Surrendered on 9 May in Trondheim, Norway. Transferred to Loch Ryan on 29 May. Transferred to Lough Foyle on 31 October prior to move to USSR. Sailed under own power with RN crew and escort on 24 November. Arrived Libau on 4 December.
U-1231 Surrendered from sea in Loch Eriboll on 14 May. Transferred to Lough Foyle. Sailed under own power with RN crew and escort on 24 November. Arrived Libau on 4 December.
U-1305 Surrendered from sea in Loch Eriboll on 10 May. Transferred to Lough Foyle. Sailed under own power, but with RN crew and escort on 24 November. Arrived Libau on 4 December.
U-2353 Surrendered on 9 May in Kristiansand (S), Norway. Transferred to Loch Ryan on 29 May. Transferred to Lough Foyle on 31 October prior to move to USSR. Sailed with RN crew under tow by HMS Riou on 24 November. Arrived Libau on 4 December.
U-2529 Surrendered on 9 May in Kristiansand (S), Norway. Transferred to Lough Foyle on 3 June. Sailed with RN crew under tow by HMS Zephyr on 24 November. Arrived Libau on 4 December.
U-3035 Surrendered on 9 May in Stavanger, Norway. Transferred to Lough Foyle on 31 May. Sailed with RN crew under tow by HMS Tremadoc Bay on 24 November. Delayed in Rosyth, Scotland for repairs from 28 November until 7 December. Arrived Libau on 14 December.
U-3041 Surrendered on 9 May in Horten, Norway. Transferred to Lough Foyle on 3 June. Sailed with RN crew under tow by HMS Narborough on 24 November. Delayed in Kristiansand (S), Norway for repairs from 29 November until 5 December. Arrived Libau on 10 December.
U-3515 Surrendered on 9 May in Horten, Norway. Transferred to Lough Foyle on 3 June. Sailed with RN crew under tow by HMS Icarus on 6 December. Delayed in Rosyth, Scotland for repairs from 11 December until 26 January 1946. Arrived Libau on 2 February 1946.
Comprehensive details of "Operation Cabal", based on Admiralty source Documents (see PRO Kew File ADM 116/5491), are published in Volume 8 of the U-Boat Archive Series by The Military Press in 2005. The story was originally researched and compiled by David Lees, and then edited by Jak Mallmann Showell.
Also, production of this note would not have been possible without the invaluable assistance of Terry Andrews of Milton Keynes, who kindly provided me with the Report from the CO of HMS Icarus which describes the problems relating to the transit of U-3515, a copy of which is held in the UK National Archives at Kew in File ADM 1/19405.
This article was published on 26 Aug 2010.