| Conflict: | The Second World War |
| Partof: | Convoy SC 7, the Battle of the Atlantic |
| Date: | 16–19 October 1940 |
| Place: | Western Approaches |
| Result: | German victory |
| Combatant2: |  United Kingdom |
| Commander1: | Karl Dönitz |
| Commander2: | Lachlan Mackinnon |
| Strength1: | 8 U-boats |
| Strength2: | 35 ships 5 escorts |
| Casualties1: | None |
| Casualties2: | 142 men killed 20 merchant ships sunk 6 merchant ships damaged |
SC 7 was the code name for a large Allied convoy in the Second World War comprising 35 merchant ships and six escorts, which sailed eastbound from Sydney, Nova Scotia, for Liverpool and other British ports on 5 October 1940. While crossing the Atlantic, the convoy was attacked by one of the first U-boat wolfpacks. The escorts were overwhelmed, twenty of the 35 cargo vessels were sunk and two were damaged, with 141 lives lost. The disaster demonstrated the potency of wolfpacks (attacking in numbers) and the inadequacy of British anti-submarine operations.
The slow Convoy SC 7 left Sydney, Nova Scotia on 5 October 1940 bound for Liverpool and other British ports. The convoy was to make but several merchant ships were much slower, reducing its speed. The convoy consisted of older, smaller ships, mostly with cargoes of bulk goods. Much of the freight on these ships originated on Canada's east coast, especially from points to the north and east of Sydney. Typical cargoes included pit props from eastern New Brunswick for British coal mines, lumber, pulpwood, grain from the Great Lakes ports, steel and steel ingots from the Sydney plant and iron ore from Newfoundland, bound for the huge steel plants of Wales. The largest ship in the convoy was the oil tanker, belonging to the Admiralty, which was bound for the Clyde with fuel for the Royal Navy. Another ship, the British, carried a valuable cargo of trucks.
Many of the ships were British but the convoy included Greek, Swedish, Norwegian and Dutch vessels. The convoy commodore, Vice Admiral Lachlan MacKinnon, a retired naval officer who had volunteered for war service, sailed in, a British ship of 2,962 GRT. Mackinnon was in charge of the good order of the merchant ships but did not command the escort. The sloop was sole naval escort for the first three quarters of the journey. There was no aircraft protection in 1940 for Allied ships in the Atlantic Ocean after leaving coastal regions. Scarborough would have had little chance against a surface attack by a German raider. Many of the merchant ship captains were resentful at having to sail in convoy and would have preferred to take their chances on their own, rather than risk such a slow crossing with a weak escort. They were often uncooperative; at one point early in the voyage Scarboroughs captain was shocked to find a Greek merchant ship in the convoy travelling at night with her lights on.
The convoy sailed on Saturday 5 October 1940. On the first day, one ship, dropped out with mechanical trouble and returned to port. The convoy "ran into a gale" on 8 October and then were engaged by U-boats. As bad weather set in on 11 October, several ships became separated and were forced to sail independently., was a small Canadian Laker of 1,813 GRT, with a cargo of lumber destined for Scotland. She was sighted by on 16 October and sunk. The Greek freighter was seen by and sunk on the 17 October but, another Laker, rescued survivors from Aenos, before arriving at Rothesay on 19 October. A fourth straggler regained the convoy on 15 October.
On 17 October, as the convoy entered the Western Approaches, Scarborough was joined by the sloop and the new corvette . Later that day they were sighted by, which attacked, sinking two ships, including the tanker Languedoc. Scarborough drove U-48 deep so she was unable to shadow or report but the attack continued for too long and the convoy moved so far ahead that Scarborough was unable to rejoin. On 18 October, Convoy SC 7 was joined by the sloop and the corvette, with Leith assuming command. Later that day, U-38 sighted the convoy and attacked, damaging . Leith and Heartsease attacked without success, though U-38 was driven off and Heartsease was detailed to escort Carsbreck home, weakening the escort further.
On the night of 18/19 October,,,, and made a concerted attack. U-99 and U-100 were captained by two famous aces, Korvettenkapitäns Otto Kretschmer and Joachim Schepke. The attack was coordinated from Lorient by Admiral Karl Dönitz the Befehslshaber der Unterseeboote (Commander, U-boats) and his staff. An early casualty was the iron ore ship,, bound for Cardiff, Wales. With her heavy cargo, she sank quickly, taking all 36 crew members with her. Later that night, Convoy SC 7 lost many of its members, including Empire Brigade with her cargo of trucks and six of her crew and with her cargo of steel ingots from Sydney. She sank quickly as well, taking with her 38 of her 39-man crew. Also among the casualties was the commodore's ship, Assyrian, which went down with 17 crew (Mackinnon was rescued after a long immersion in the chilly waters). In all, 16 ships were lost in this six-hour period.
On 18 October, was torpedoed by U-101 and was abandoned. She was torpedoed again on 19 October by U-100 but remained afloat. She was towed to the Clyde and later repaired at Greenock. The escorts were unable to prevent any of these losses; their responses were uncoordinated and ineffective. They never realised that the attacking submarines did not attack submerged or from outside the convoy but were actually running surfaced between the ships inside the convoy. The escorts were unable to mount any serious attacks on the U-boats and spent much of their time rescuing survivors. During 19 October, the escorts, loaded with survivors, gathered together those ships that remained. Fowey collected eight ships and made for the Clyde, arriving there a few days later. Scarborough passed through the scene of the battle later on 19 October; she found wreckage, but no survivors. Later that afternoon Leith met Heartsease, still escorting the damaged Carsbreck; together they headed for Gourock, Renfrewshire, collecting two more stragglers on the way. Bluebell with over 200 survivors on board, headed directly for the Clyde, arriving on 20 October.
SC 7 had lost 20 ships out of 35, of which seven fell to Kretschmer's U-99. The total tonnage lost was 79,592 GRT. The arrival of convoy HX 79 in the vicinity had diverted the U-boats and they sank twelve ships from Convoy HX 79 that night. No U-boats were lost in either engagement. The loss of 28 ships in 48 hours made 18 and 19 October the worst two days for shipping losses in the entire Atlantic campaign. The attack on Convoy SC 7 was a vindication of the U-boat Arm's wolfpack tactic and was the most successful U-boat attack of the Atlantic campaign. Convoy tactics were rudimentary at this early stage of the war. The escorts' responses were uncoordinated, as the ships were unused to working together with a common battle plan. Command fell to the senior officer present and could change as each new ship arrived. The escorts were torn between staying with the convoy, abandoning survivors in the water, as Defensively Equipped Merchant Ships (DEMS) regulations demanded and picking them up, leaving the convoy unprotected and risking being torpedoed themselves. In the German semi-official history, Germany and the Second World War (2015), Bernd Stegemann wrote that the U-boats had their best success per-day-at-sea in October 1940. During the winter of 1940–1941 the U-boats had less success due to the seasonal weather, the British–US destroyers-for-bases deal, the arrival of the first corvettes, the addition of radar sets and radio-telephones to British destroyers and the slow increase in the number of Coastal Command aircraft.
Germany's Initial Conquests in Europe
. 2015 . 1991 . Militärgeschichtliches Forschungsamt [Research Institute for Military History] . Falla . P. S. . trans. pbk. Clarendon Press, Oxford . II . Freiburg im Breisgau . en . McMurry . Dean S. . Osers . Ewald . 978-0-19-873834-3.