'Roundel' was the British naval undertaking to ensure the passage of the JW.66 and RA.66 Arctic convoys to and from Murmansk in the northern USSR (16 April/8 May 1945).
The JW.66 convoy was the last outbound Arctic shipping movement to take place within the period of hostilities in of World War II, and the undertaking came under the overall control of Rear Admiral A. E. M. B. Cunninghame-Graham, commanding the 10th Cruiser Squadron. The supporting forces included the escort carriers Premier and Vindex, the light anti-aircraft cruiser Diadem, the destroyers Offa, Zealous, Zephyr, Zest, Zodiac, Canadian Haida, Huron and Iroquois, and Free Norwegian Stord of the 2nd Destroyer Flotilla, the sloop Cygnet, and the corvettes Alnwick Castle, Bamborough Castle, Farnham Castle, Honeysuckle, Lotus, Oxlip and Rhododendron of Commander D. M. MacLean’s 8th Escort Group. The frigates Anguilla, Cotton, Goodall, Loch Insh and Loch Shin of Lieutenant Commander E. W. C. Dempster’s 19th Escort Group were also sent ahead of the convoy to clear a way through the expected U-boat concentration.
On 17 April the British began 'Trammel' to lay a deep minefield off the mouth of the Kola inlet in an effort to destroy and deter U-boats operating in this chokepoint on the approach to Murmansk. The cruiser minelayer Apollo and the minelaying destroyers Obedient, Opportune and Orwell, together with the light anti-aircraft cruiser Dido as escort, departed Scapa Flow in the Orkney islands group and reached the Kola inlet on 21 April to refuel. With this completed on the following day, the British force proceeded to lay a field of 276 mines. The 19th Escort Group co-operated to keep the U-boats away from the minelaying force, which then returned to the UK, reaching Scapa Flow on 26 April.
The B-Dienst radio intercept and decryption service had meanwhile discovered the sailing of the JW.66 convoy with 27 laden ships, and the U-boat arm deployed U-286, U-295, U-307, U-313, U-363 and U-481 to a planned ambush position to the west of Bjørnøya as the 'Faust' wolfpack.
In the period up to 21 April German air reconnaissance was not able to locate the convoy, so the U-boats were moved to positions off the Kola inlet, where the initial six boats were supplemented by U-278, U-294, U-312, U-318, U-427, U-711, U-716, U-968, U-992 and U-997. The Germans thus had a strength of 16 U-boats available for action against the JW.66 convoy. On 21/22 April some of these U-boats came into contact with the Soviet PK.9 coastal convoy from Petsamo to Kola: the convoy comprised two ships escorted by the destroyers Karl Libknekht, Derzky, Zhestkiy and Dostoinyi, two minesweepers, six submarine chasers, four motor torpedo boats and a Free Norwegian group comprising the corvette Eglantine and the anti-submarine trawlers Karmøy, Jeløy and Tromøy.
Oberleutnant Hans Lehmann’s U-997 sank the 1,603-ton Soviet Onega and torpedoed the 4,287-ton Norwegian Idefjord, which was then taken in tow. Further attacks by U-294, U-481 and U-997 were frustrated by the escort vessels, which avoided several torpedoes fired at them, although Kapitänleutnant Klaus Andersen’s U-481 claimed to have sunk a trawler on 19 April. British counterattacks damaged only one U-boat, which confirmed earlier indications that although the escort vessels could usually force the U-boats to remain submerged, the difficult sonar conditions always encountered in northern Russian waters made it extremely hard to destroy them.
On 25 April the Soviet destroyers Uritskiy, Karl Libknekht, Kuybyshev, Zharkiy, Zhestkiy, Derzkiy and Dostoinyi, minesweeper T-113 and five submarine chasers joined the escort of the JW.66 convoy. Only U-711, which had penetrated farthest into the Kola Inlet, was able to launch torpedoes, though without success, at the convoy’s merchant vessels, which reached harbour on 25 April.
Kapitänleutnant Hans-Günther Lange’s U-711 claimed to have sunk a small ship on 19 April. Zhestkiy, the minesweeper T-116 and a submarine chaser reported that they had made attacks on U-boats.
The homeward-bound counterpart of the JW.66 convoy was the RA.66 convoy of 27 unladen ships, and the passage of these ships involved the last convoy battle of World War II.
The RA.66 convoy was shielded by a close escort force comprising the sloop Cygnet, the corvettes Alnwick Castle, Bamborough Castle, Farnham Castle, Honeysuckle, Lotus, Oxlip and Rhododendron, and a fighting escort comprising the escort carriers Premier and Vindex, the light anti-aircraft cruiser Bellona, and the destroyers Zealous, Zephyr, Zest, Zodiac, Canadian Haida, Huron and Iroquois, and Free Norwegian Stord accompanied by the oiler Blue Ranger and the destroyers Obedient, Offa and Orwell. In addition there was the 19th Escort Group with the frigates Anguilla, Cotton, Goodall, Loch Insh and Loch Shin.
On 29 April, before the departure of the convoy, Allied escort vessels, supported by Soviet destroyers Zharkiy, Zhestkiy, Derzkiy and four submarine chasers, were deployed to the waters off the Kola Inlet in an effort to drive off the waiting U-boat concentration, which comprised U-278, U-286, U-307, U-312, U-313, U-318, U-363, U-427, U-481, U-711, U-716, U-968, U-992 and U-997.
Oberleutnant Ernst Heydemann’s U-268 and Oberleutnant Erich Krüger’s U-307 were sunk by the frigates Anguilla, Cotton, Loch Insh and Loch Shin. Oberleutnant Otto Westphalen’s U-968 just missed the corvette Alnwick Castle but torpedoed the frigate Goodall, which was also hit by Oberleutnant Willi Dietrich’s U-286, and sank her. U-427 just missed the destroyers Haida and Iroquois, and then had to survive a long and determined counterattack during which 678 depth charge explosions were counted. U-313 was attacked by Soviet submarine chasers, and managed to escape.
As a result of these actions the U-boats were driven off, and therefore could not approach the convoy. Then German air reconnaissance was unable keep contact with the convoy, and the Germans accordingly terminated their effort to attack the RA.66 convoy, all of whose ships reached the estuary of the Clyde river on 8 May.
It is worth noting that one more convoy was sailed in each direction on the Arctic route after the end of World War II. As many U-boats were still at sea, escorts were provided in the normal manner but on a reduced scale. No incidents took place on either convoy, and the tempestuous saga of the Arctic convoys ended quietly on 31 May, when the 25 ships of the RA.67 convoy steamed into the Clyde with all lights burning.