The slaughter of convoys SC 7 and HX 79

On the night of 18–19 October 1940, in the north-western approaches to the British Isles, five German submarines slipped on the surface between the columns of the slow convoy SC 7, bound from Canada to Liverpool. Within a few hours they had sunk sixteen ships. Less than a day later, on the night of 19–20 October, some of the same U-boats, joined by fresh ones, fell upon the fast convoy HX 79 from Halifax and sank twelve more ships, even though this time it was protected by a strong escort. The Germans did not lose a single boat in either attack. In all, SC 7 lost 20 of its 35 ships and HX 79 lost 12 of 49. The sinking of 28 ships in two nights was the greatest U-boat success of the first phase of the Battle of the Atlantic and one of the heaviest blows British shipping suffered in the entire war.

War chronologies usually record under 29 October only a general note about “very heavy convoy losses in this period, as the number of U-boats grows”. That date is a summary of the whole month rather than the day of any particular event. The heaviest attacks of October fell on 16–20 October, culminating on the night of 18–19 October. The second part of the note needs correcting: the number of German submarines in the Atlantic at that time was not growing but was still very small. The heavy losses stemmed not from the number of U-boats but from the way they were used.

Few boats, new tactics

When war broke out, Karl Dönitz had 57 submarines, of which about twenty were fit for operations on the open ocean. New construction barely made good the losses of the first year of the war, some thirty boats, and the new submarines, which entered service in growing numbers from the autumn of 1940, spent many months training their crews in the Baltic. In the autumn of 1940, therefore, Dönitz still had only twenty-odd front-line boats, and since some of them were always on passage to or from their hunting grounds or in refit, there were usually only a handful to a dozen or so in the Atlantic at any one time. He reached his lowest number of front-line boats – 22, by his own account – in February 1941. The number of U-boats did not begin to rise quickly until the second half of 1941.

These few boats, however, were operating in far better conditions than a year earlier. After the Armistice of Compiègne they gained bases on the Bay of Biscay, above all at Lorient, which cut hundreds of miles off the passage to the hunting grounds and lengthened their patrols. Since 17 August the total blockade of the British Isles proclaimed by Berlin had been in force. From the autumn Italian submarines from the BETASOM base at Bordeaux were also operating in the Atlantic, so far with little success.

Most important of all was the change of tactics. Instead of lying in wait for ships singly and attacking submerged by day, the U-boats were deployed in a patrol line across the probable route of a convoy. The boat that sighted it did not attack at once but shadowed the convoy and reported its position, while Dönitz’s headquarters in France directed the others towards it. They attacked at night, on the surface, often from inside the convoy’s formation. A surfaced submarine with its low conning tower was almost invisible in the dark, and the British ASDIC (sonar) could detect only submerged boats. The escorts did not yet have radar. An attack organised in this way, later known as the “wolf pack”, had already proved itself in September against convoy HX 72, which lost eleven ships. In October Dönitz applied it on a larger scale.

The British, for their part, were short of escort vessels. Many of their destroyers were still waiting in the ports of the east and south coasts for the German invasion; only in October, when Hitler postponed it until the spring, could the Admiralty begin moving them to the Atlantic. The fifty old American destroyers from the destroyers-for-bases deal were still being made ready for service, and the new Flower-class corvettes had freshly assembled, untrained crews. The escorts did not form permanent groups: they were assigned to a convoy individually, did not know one another, had no common plan of action and no radio-telephone link, and command fell to the senior officer present, who might change with the arrival of another ship.

The slow convoy SC 7

Convoys designated SC (for Sydney, Cape Breton) had been assembled since August 1940 in the port of Sydney on Cape Breton Island in Nova Scotia, for ships too slow to sail in the fast HX convoys from Halifax. SC 7 left Sydney on 5 October 1940 (some accounts give 4 October). It consisted of 35 merchant ships, mostly old and small, chiefly British but also Greek, Norwegian, Swedish, Dutch and Canadian. They carried what Britain needed to wage war: pit props for the coal mines, timber, pulpwood, grain, steel and steel ingots from the Sydney steelworks, and iron ore from Newfoundland for the Welsh steelworks. The largest ship was the Admiralty tanker Languedoc (9,512 GRT) with fuel for the fleet, while Empire Brigade carried lorries. The convoy was meant to sail at 8 knots, but the slowest ships could barely keep up that speed.

The convoy commodore, responsible for order among the merchant ships, was a retired vice admiral, Lachlan Mackinnon, who had volunteered for service and sailed in the small steamer Assyrian. For most of the ocean crossing the escort consisted of a single ship, the sloop HMS Scarborough, which could not have defended the convoy against either a surface raider or several submarines. Many merchant captains were reluctant to sail in convoy, would have preferred to sail alone and faster, and did not always keep to the discipline; one of the Greek ships sailed at night with its lights on.

After a storm on 11 October several ships became separated from the convoy. Two of them were the first to be lost: on 16 October Georg-Wilhelm Schulz’s U-124 sank the small Canadian ship Trevisa, laden with timber, and on 17 October Heinrich Liebe’s U-38 sank the Greek Aenos.

The first attacks: 17 and 18 October

On 17 October, as the convoy entered the Western Approaches, Scarborough was joined by the sloop HMS Fowey and the new corvette HMS Bluebell. That same day the convoy was sighted by Heinrich Bleichrodt’s U-48, the same boat that a month earlier had sunk the liner City of Benares. Bleichrodt sent a sighting report and attacked, sinking the tanker Languedoc and the steamer Scoresby. Scarborough forced U-48 to dive, and a Short Sunderland flying boat of RAF Coastal Command prevented it from resuming the chase. The sloop, however, hunted the submarine for so long that the convoy drew away, and Scarborough never caught up with it again.

Bleichrodt’s report was enough for Dönitz. Across the convoy’s path, east of the islet of Rockall, he set up a patrol line of five boats: Engelbert Endrass’s U-46, Otto Kretschmer’s U-99, Joachim Schepke’s U-100, Fritz Frauenheim’s U-101 and Karl-Heinz Moehle’s U-123. Among them were the most successful commanders of the German submarine arm. On 18 October the convoy was joined by the sloop HMS Leith, whose captain took command of the escort, and the corvette HMS Heartsease. That day SC 7 was also found by Liebe’s U-38, which damaged the steamer Carsbreck. Heartsease escorted the damaged ship away, weakening the escort still further. On the evening of 18 October, therefore, the convoy was defended by three ships: Leith, Fowey and Bluebell.

The night of 18–19 October

Late in the evening the convoy ran into the patrol line, and five U-boats attacked almost simultaneously, on the surface, from different directions. Endrass sank the British Beatus and two Swedish ships, Convallaria and Gunborg. Frauenheim first torpedoed Blairspey, which stayed afloat thanks to her cargo of timber, and later sank Creekirk, which, laden with iron ore, went to the bottom within seconds with her entire crew of 36, as well as the Dutch Soesterberg and Assyrian. Seventeen men from the commodore’s ship were lost; Mackinnon himself was picked up after a long time in the water.

Kretschmer sank the most ships. His U-99 got into the middle of the convoy and, moving between the columns, fired at close range, in keeping with the principle attributed to him: “one torpedo, one ship”. He sank Empire Miniver, the Greek Niritos, Fiscus with her steel ingots, from whose crew of 39 only one man survived, Empire Brigade with her lorries, the Norwegian Snefjeld and the Greek Thalia; Clintonia, which he had torpedoed, was later finished off by U-123. Moehle sank the Dutch Boekelo, Shekatika and Sedgepool. Schepke, who reached the convoy later, damaged several ships but sank none on his own. According to the tallies of uboat.net, U-99 sank six ships from SC 7, although some authors credit it with seven, counting Clintonia.

The escort was helpless. Its commanders did not realise that the submarines were attacking on the surface from inside the convoy, and searched for them outside the formation, dropping depth charges blindly and firing star shell. Torn between the duty to protect the convoy and the rescue of survivors from the sinking ships, they mostly chose the latter. The convoy broke up into small groups of ships. On the morning of 19 October Fowey gathered eight of them and led them to the mouth of the Clyde, Leith and Heartsease rounded up stragglers, and Bluebell, with more than two hundred survivors on board, made straight for Scotland. The damaged Blairspey was towed to the Clyde and, after repairs at Greenock, returned to service.

In all, convoy SC 7 lost 20 of its 35 ships, totalling 79,592 GRT, and two more were damaged. Sixteen ships went down in a single night. According to English-language tallies, 141 seamen were killed. The U-boat commanders, reporting the same ships in the confusion of the night attacks, claimed even more: Dönitz’s staff at first assumed that some 30 ships had been sunk.

Convoy HX 79

Behind SC 7, on the same route, came the faster convoy HX 79. It left Halifax on 8 October 1940, and after it had been joined by groups of ships from Sydney and Bermuda, 49 ships crossed the ocean. Like the first HX convoy a year earlier and HX 72 in September, on the open ocean it was protected only by ships intended against surface raiders: two armed merchant cruisers, HMS Alaunia and Montclare, and the Dutch submarine O 14.

The Admiralty, knowing by now what had befallen SC 7, expected an attack and sent out to meet the convoy the ships that had just escorted the westbound convoy OB 229. They took over HX 79 from the armed merchant cruisers before noon on 19 October. By the standards of the day it was a very strong escort: two destroyers, HMS Whitehall and Sturdy, the minesweeper HMS Jason, four corvettes, Hibiscus, Heliotrope, Coreopsis and Arabis, three anti-submarine trawlers and the Dutch submarine O 21. These ships, however, had never worked together before, the corvettes were new and had inexperienced crews, and the presence of a friendly submarine only added to the confusion: the escorts twice mistook it for the enemy.

On 19 October the convoy was sighted by Günther Prien’s U-47, which had set out on a new patrol with a full load of torpedoes. Prien sent a report and shadowed the ships. U-99, U-101 and U-123 had already fired all their torpedoes at SC 7 and were returning to Lorient, but Dönitz directed against HX 79 the boats that still had some: Schepke’s U-100, Endrass’s U-46, Liebe’s U-38 and Bleichrodt’s U-48. By nightfall five had gathered.

On the evening of 19 October and through the night of 19–20 October the events of the previous night were repeated. According to the tallies of uboat.net, Liebe sank the British Matheran and the Dutch Bilderdijk; Prien sank Uganda, Wandby, La Estancia and Whitford Point and damaged the tanker Shirak, which Bleichrodt finished off, as well as the tanker Athelmonarch, which managed to reach port. Endrass sank Ruperra, carrying steel scrap and aircraft, and the new Swedish tanker Janus, and Schepke sank two tankers, Caprella and Sitala, and the ship Loch Lomond, which had stopped to rescue survivors from Matheran. The attribution of individual sinkings to particular commanders differs in some accounts, because several ships were hit by more than one boat. The escort, which as on the previous night searched for the enemy under water and busied itself with survivors, did not sink a single U-boat.

HX 79 reached Liverpool on 23 October without further losses. It had lost 12 of its 49 ships, about a quarter, totalling 75,069 GRT. The heaviest loss of life came with the sinking of Ruperra, from which seven men were rescued, and of Whitford Point, from which only a few survived. Once again the Germans overestimated their success: the commanders claimed seventeen ships sunk. In the same days U-124 sank two ships from the westbound convoy OB 229, and on 15–18 October U-93, U-138 and U-48 sank several ships from convoys OA 228 and OB 228, sailing westwards from the British Isles.

“The Night of the Long Knives”

German propaganda presented the attacks on SC 7 and HX 79 as a single great convoy battle, and the night of 18–19 October came to be called “the Night of the Long Knives” (Nacht der langen Messer), the name under which these events still appear in some publications. The commanders who returned to Lorient with empty torpedo tubes became newsreel heroes. On 20 October Prien became the first officer of the Kriegsmarine to receive the Knight’s Cross with Oak Leaves, and Kretschmer, then the most successful U-boat commander, received the same decoration at the beginning of November.

The toll of those days was indeed exceptional. In five days the submarines sank 32 ships from the two convoys and, counting ships sailing independently and those from westbound convoys, close to forty. According to the tallies of uboat.net, in the whole of October 1940 U-boats sank 60 ships totalling more than 342,000 GRT and damaged 12 more – more than in September (57 ships, 285,000 GRT). The German semi-official history of the war judges that in October 1940 the submarines achieved their best results of the entire war measured per day at sea. A mere nine boats took part in the attacks on SC 7 and HX 79, counting U-124, which sank the stragglers from SC 7.

Place in the war

The attacks on SC 7 and HX 79 showed both sides what the first year of the war at sea had taught them. Dönitz concluded that the group tactics had been fully vindicated, and from then on he built his whole war against the convoys upon them. The British realised that the number of escort vessels alone, even as large as HX 79’s, was not enough if they were not trained to work together. The Admiralty began to form permanent escort groups with a single commander and common tactics, to equip ships with radio-telephones and radar, to move escort and aircraft bases to Iceland and Northern Ireland, and in February 1941 it moved Western Approaches Command from Plymouth to Liverpool. With the postponement of the invasion, destroyers were returning to the Atlantic, and as Flower-class corvettes and American destroyers arrived, the escorts grew month by month.

The U-boats’ autumn successes continued for a few more weeks. On 28 October U-32 finished off the liner Empress of Britain, damaged two days earlier by a German Focke-Wulf Fw 200 Condor aircraft – the largest merchant ship sunk by a U-boat in this war – and on 1 and 2 December several U-boats shattered convoy HX 90. In the winter results fell, owing to storms, the small number of boats and the strengthening defences. In March 1941 the “happy time” came to an abrupt end: around 7 March Prien was lost with U-47, and on the night of 16–17 March, during an attack on convoy HX 112, the destroyer HMS Vanoc rammed U-100, killing Schepke, while HMS Walker sank U-99 and took Kretschmer prisoner. Yet the Battle of the Atlantic went on until the end of the war in Europe, and its hardest months still lay ahead of the British. The autumn of 1940 showed that the island which had defended itself in the air could still lose at sea – and that a handful of well-led submarines was enough to bring that about.