'Thwart' (ii) was the British overall designation, otherwise 'Covered' and successor to 'Player', for naval operations in the Indian Ocean to locate and destroy the U-boat supply vessel Charlotte Schliemann known to be making her way back to Germany (19 January/0 February 1944).
The ships involved in this undertaking included the escort carrier Battler, heavy cruiser Suffolk, light cruisers Kenya and Newcastle, destroyer Nepal, frigate Bann, and armed merchant cruiser Canton.
The 7,747-ton Charlotte Schliemann, which had been completed in 1928 as a tanker, had reached Las Palmas in the Spanish Canary islands group on 31 August 1939 with 10,800 tons of fuel oil, and remained at Las Palmas until a time early in 1942. In this period she seems to have supplied fuel only to one Italian submarine. On 24 February Charlotte Schliemann departed the Canary islands group to supply the German surface raiders Stier and Michel (4,778 and 4,740 tons respectively). The former was known to the German navy as HSK-6 and Schiff 23, and to the British as Raider J, and the latter to the Germans as HSK-9 and Schiff 29, and to the British as Raider H, and between April and August Charlotte Schliemann linked with each of them at least three times in the South Atlantic.
It was on 10 May 1942 that Stier had left Germany for operations in the Atlantic. Moving by stages down the English Channel, and after an engagement with British coastal forces on 13 May which resulted in the loss of two S-boote and one motor torpedo boat, Stier reached Royan in German-occupied France on 19 May. From here she departed for a raiding cruise in the South Atlantic as the last German raider to break out in the Atlantic, and she also became the first German surface combatant to be sunk by US forces. On 4 June 1942 Stier had sunk the 4,986-ton British ship Gemstone, and two days later a valuable Panamanian tanker of more than 10,000 tons. Stier passed the merchant seamen captured on the two ships to Charlotte Schliemann. However, after a cruise of only 4.5 months, in which she had engaged and sunk three ships (Gemstone, 10,170-ton Stanvac Calcutta, 7,250-ton Dalhousie), she had a fatal encounter on 27 September with the 7,181-ton US cargo ship Stephen Hopkins on passage from Cape Town to Paramaribo. Closing in foggy conditions, the ships sighted each other at about 08.52 at a distance of 4,000 yards (3660 m). The German captain sent his men to action stations and, suspicious of the unidentified vessel, the US master did the same.Stephen Hopkins had a small defensive armament of one stern-mounted 4-in (102-mm) gun and several machine guns, but from the start of the action at about 08.55 put up a spirited defence. The US ship scored several hits on Stier, damaging her engines and steering gear before, overwhelmed by fire from Stier, whose main armament was six 150-mm (5.91-in) guns, she drifted away and by 10.00 had sunk. Some 42 of her crew were killed in the action, three more died later, and the 16 survivors finally reached Brazil 31 days later.
Stier too had suffered fatal damage, though, and was unable to make headway or steer. Her captain decided to abandon ship. The scuttling charges were set and Stier sank at 11.40. All but two of the German ship’s crew survived: they were rescued by the supply ship Tannenfels, which was accompanying Stier at the time of the action.
On 19 April Michel sank the 7,469-ton British tanker Patelle carrying nearly 10,000 tons of oil fuel from Trinidad to Cape Town, and only four days later sank the 8,684-ton US tanker Connecticut, also bound for Cape Town. On 20 May Michel used her guns to sink the Norwegian freighter Kattegat, and on 6 June Michel's small attack boat made a night attack on US ship George Clymer, and believed that this vessel had been sunk. But George Clymer made a distress signal picked up by the British naval headquarters at Freetown, Sierra Leone, which detached the 22,209-ton armed merchant cruiser Alcantara from escorting the WS.19 convoy. On 7 June Alcantara found George Clymer still afloat and, after rescuing her crew, sank the badly damaged merchant ship on 12 June.
Five days later Michel sank the British ship Lylepark to the south of Ascension island. Michel then met Charlotte Schliemann and Doggerbank: the latter was the ex-British Speybank, which had been captured in the Indian Ocean early in 1941 by Atlantis, another German raider, sent into Bordeaux for conversion as an auxiliary minelayer. The three ships remained in company for a week, Michel taking on fuel and supplies, and transferring her prisoners to Charlotte Schliemann.
Michel next operated to the east of Ascension island, and on 15 July sank the Union Castle line’s 8,006-ton passenger and cargo ship Gloucester Castle in a gun and torpedo attack; the British ship lost 90 dead. On the following day, the German raider sank the 7,893-ton US tanker William F. Humphrey returning to Trinidad in ballast, and used Esau, her small attack craft, in a night attack which damaged the 7,984-ton Norwegian tanker Aramis. The tanker managed to transmit a raider report and tried to escape, but after a one-day pursuit Michel sank her. The raider then steamed to the south and met firstly Stier and then Charlotte Schliemann, which again took off Michel's prisoners.
When Doggerbank supplied Michel on 21 June, she also transferred most of her remaining supplies to Charlotte Schliemann and embarked 177 mercantile prisoners captured by raiders. With these on board, Doggerbank sailed firstly for Batavia (Djakarta) in Java and thence Japan, where she became a blockade runner. Doggerbank's career ended on 3 March 1943 off the Canary islands group, when Oberleutnant Hans-Joachim Schwantke’s U-43 sighted, misidentified and sank her.
Michel also operated in the Indian Ocean and, after a successful cruise of 11.5 months, arrived in Japan during March 1943. In 346 days she had sunk 15 Allied ships totalling some 99,000 tons.
On 27 August 1942 Charlotte Schliemann refuelled Stier for the last time, and then headed for Japan. In June 1943 Charlotte Schliemann was refuelling at least seven U-boats in the area to the south-east of Madagascar. These boats had been operating in the waters off the Cape of Good Hope, and after refuelling from Charlotte Schliemann moved to the north and north-east in search of targets in the Mozambique Channel and steaming between the Cape of Good Hope and India or Ceylon. In the last 10 days of January 1944 four U-boats working the Gulf of Aden and the waters off the Maldive islands sank six independently routed British ships.
Two of these boats had refuelled from Charlotte Schliemann, when in February a Consolidated Catalina flying boat from Mauritius sighted the German supply ship. As a result, on 9 February 1944 the destroyer Relentless, in 'Canned' (ii), intercepted and torpedoed Charlotte Schliemann, whose crew appreciated the hopeless nature of the situation and therefore scuttled their crippled ship in the area to the south-east of Mauritius. The German captain and 40 of his crew were rescued by Relentless, while 47 other men, in four different boats, set off in an attempt to reach land. Two boats finally reached the east coast of Madagascar, after 26 and 30 days at sea, and the two other boats were never seen again.