Convoy HG-76

HG 76 (19 to 23 December 1941) was an Allied convoy of the HG (Homeward from Gibraltar) series, during the Second World War. It was notable for the destruction of five German U-boats (the true total was not known to the British until after the war).

Two Focke-Wulf Condor long-range reconnaissance aircraft were shot down by Martlet fighters. The fighter cover was provided by the escort carrier , which was sunk during the voyage along with a destroyer and two merchant ships. Despite the loss of the escort carrier, it was regarded as the first big convoy victory for the Allies in the Battle of the Atlantic.

Background

The attack on HG 76 was the last in a series of U-boat pack attacks on Gibraltar convoys which had started in the summer of 1941. Before this the U-boat Arm (, UBW) had only enough boats operational to form one patrol line at a time and their focus was on the North Atlantic convoy route. Gibraltar convoys had suffered only occasional adventitious attacks by individual U-boats that had met them while crossing their route. By the summer 1941 U-boat Command ( BdU) had sufficient boats to form several patrol lines but this coincided with Hitler ordering U-boats into the Mediterranean to support Axis forces operating in North Africa and attack the Gibraltar traffic. This phase of the campaign had commenced with a pack attack on OG 69.

For the Allies the introduction of stable escort groups had created the conditions the development of convoy protection tactics, giving a measure of success in countering the wolf pack threat. It was recognized that air cover was needed to counter shadowing aircraft and to seek out approaching U-boats and for reinforcement to convoys under attack to provide sufficient ships to hunt U-boats to destruction rather than simply driving them off, as so often happened. The first requirement was met with the commissioning of HMS ''Audacity'', the first in a series of merchant aircraft carriers, the second by reinforcing the escorts and by the formation of an ASW Strike Force at Gibraltar, which would sweep ahead of a homeward bound convoy, to attack and destroy patrolling U-boats. The new measures had been introduced by the time HG 76 sailed.

Prelude

HMS ''Audacity''

''Audacity'' participated in the escort of convoy OG 76 of twenty merchant ships, which sailed from Liverpool for Gibraltar on 31 October. The escort carrier embarked 802 Naval Air Squadron (802 NAS) of the Fleet Air Arm with eight Martlets and ten pilots. The fighters were usually split into standing patrols of two aircraft, which flew over the convoy for about two hours, searching for U-boats and Condors, the danger mainly coming from deck landings. The weather was atrocious and at times pitched the flight deck and rolled it through spray swept over the deck. Two Martlets took off on patrol and one managed a safe landing but the other touched down when the stern was rising and was thrown overboard, the pilot being rescued just before the Martlet sank.

On 8 November, ''Kampfgeschwader'' 40 (KG 40) sent six Focke-Wulf Condor aircraft to locate convoy SL 91, bound for Liverpool from Freetown, Sierra Leone. Near noon, the radar on ''Audacity'' detected two of the Condors and a Martlet patrol was sent to intercept. One Condor escaped into a cloud but two Martlets caught the second, which shot down one Martlet before being shot down by the other Martlet. About three hours later, another Condor was shot down by a Martlet making a head-on attack and a fourth Condor escaped. KG 40 had lost a third of its operational aircraft and failed to direct any U-boats onto either convoy, OG 76 making a safe arrival at Gibraltar late on 11 November. The presence of ''Audacity'' was now known to KG 40 and to BdU.

HG 76

HG 76 comprised 32 ships homeward bound from Gibraltar, many in ballast or carrying trade goods. The Convoy Commodore was Vice-Admiral R. Fitzmaurice in the steamship ''Spero''. The convoy had a strong escort, consisting of 36th Escort Group (Commander F. J. "Johnnie" Walker), usually composed of two sloops ( and ) and seven corvettes (''Convolvulus'', ''Gardenia'', ''Marigold'', ''Pentstemon'', ''Rhodedendron'', ''Samphire'' and ''Vetch''). Walker, a skilled anti-submarine warfare expert, had taken command of EG 36 in October and brought the group down to Gibraltar in November with OG 76. He had exercised the group there in anti-submarine patrols that had resulted in the destruction of U-433 by ''Marigold''. This force was augmented by the new escort carrier and her three escorting destroyers, , and , plus the sloops , and the corvettes ''Carnation'' and ''La Malouine'', also at Gibraltar. This made a total escort of 17 warships. A group of destroyers from Force H in Gibraltar, comprising , , and sailed as an independent U-boat hunting force.

Since August 1940, Dönitz had ended the practice of U-boats freelancing and sending only one report per day. U-boat commanders were ordered to signal whenever they found a convoy and shadow it rather than attack. The commander was to send short homing signals every thirty minutes, to guide other U-boats to the convoy. When the pack had assembled, Dönitz gave the order to attack, usually at night, so that the U-boats could fire their torpedoes on the surface. For the tactic to work, U-boats had to signal their positions to Dönitz at Kerneval (across the river from the submarine base at Lorient in Brittany). Closer to land, when Condors on tracking patrol () sighted a convoy, the wireless operator reported its position and course to the BdU and relays of Condors remained over the convoy. When the position of a convoy was established, the information was passed to the senior officer of a group of U-boats organised for pack attacks, who ordered the boat nearest to the convoy to shadow it and guide the rest by wireless. When the pack had rendezvoused near the convoy, surface attacks would be made on successive nights, the U-boats withdrawing during the day.

In mid December U boat Command was informed that a convoy was assembling at Gibraltar. German agents stationed in the Spanish city of Algeciras, in neutral Spain, were able to overlook the harbour and report any and all activity there, without hindrance from the Axis-friendly Spanish authorities.
BdU began to assemble a patrol line, code-named (Pirate), preparatory to launching a pack attack. was an group, as the previous , had disbanded following a fruitless pursuit of southbound OS 12.
comprised seven U-boats; '' U-67'' was already in position after a failed attack on OG 77; '' U-434'' and '' U-574'' from had refuelled from a clandestine depot ship in Vigo harbour, ''U-127'' and '' U-131'' had arrived from Germany and '' U-107'' and '' U-108'' from bases in France. Five of the seven were Type IX boats, which Dönitz considered unsuitable for pack attacks and five of the seven crews were inexperienced, being on their first patrols. The pack had orders to sink ''Audacity'' at all costs and was reinforced later by three more boats; U-108 sank a Portuguese freighter sailing independently on 14 December.

Battle

14–15 December

HG 76 sailed from Gibraltar on 14 December 1941, in company with a small convoy bound for Cape Town, and was reported almost immediately by German agents across the bay in neutral Spain, who reported the composition, escort strength and departure time of the convoy; BdU was confused by an agent report that the convoy had returned to port. The first sightings of HG 76 were made by U-74 and U-77, both to the Mediterranean and about to transit the Straits. U-77 sank one ship from the Cape Town convoy, but U-74 was unable to attack HG 76; Fairey Swordfish aircraft of RAF Gibraltar Command were escorting the convoy and on three occasions during the night of drove off the U-boats. The boats formed a patrol line south of Cape St Vincent but HG 76 passed through the line without detection. At Lockheed Hudson and Consolidated Catalina aircraft took over from the Swordfish and for the next two days co-operated with the 802 NAS Martlets on ''Audacity'', forcing U-boats to submerge. U-127 was detected on a routine anti-submarine sweep by a Short Sunderland from Gibraltar late in the day; next morning it was detected on Asdic by and sunk at

16–18 December

At noon on 16 December, HG 76 was sighted and its position reported by a Focke-Wulf Condor of I/KG 40 patrolling from Bordeaux, which guided U-108 to the convoy to begin reporting its position to other U-boats. During the night of the wolf pack closed in and U-574 was ordered to the area; by morning on 17 December, the convoy had passed beyond the range of Gibraltar-based aircraft and four U-boats made contact, ''U-67'' and ''U-108'' being forced away from the convoy. Just after a Martlet from ''Audacity'' sighted a surfaced U-boat about from the convoy and circled over the area for the escort ships to gain a good radar fix; a corvette made an Asdic attack to no apparent effect. At on 17 December, ''Stanley'' sighted U-131 on the surface and Walker ordered a Martlet to attack while ''Stork'', with ''Pentstemon'' and the three destroyers, made their best speed to the location. The Martlet pilot dived towards the U-boat and both opened fire at the same time, the Martlet being shot down and the pilot killed. The British ships opened fire at extreme range, U-131 was driven to the surface and sunk. Observers saw the crew of U-131 abandon the vessel before it sank at Survivors said that they had been shadowing the convoy (claiming to have spent the previous night inside the convoy, homing other U-boats) and had been the U-boat attacked earlier.

On the night of the U-boats attacked again but failed to torpedo any ships; U-107 was forced under water by ''Pentstemon'' and after a failed torpedo attack, ''U-67'' was forced to retire by ''Convolvulus''. At on 18 December, ''Stanley'' gained an Asdic contact and several ships dropped fifty depth charges. After thirty minutes U-434 surfaced and the crew abandoned ship just before it rolled over and sank north of Madeira, of the crew being rescued and taken prisoner. Before noon, the radar on ''Audacity'' indicated two aircraft and Martlets were scrambled to intercept but the guns on both aircraft jammed and the Condors escaped. The rest of the day was quiet but the Admiralty signalled that three more U-boats were en route. In the early hours of ''Stanley'' sighted U-574 astern at sent a sighting report, was hit by a torpedo and blew up. ''Stork'' following behind, swung behind the stern of ''Stanley'', gained an Asdic contact and dropped a pattern of depth charges, then turned after to attack again.

A U-boat shot to the surface ahead and a chase began; Walker tried to ram the U-boat but found that it could turn inside the turning circle of ''Stork'' nearly as fast. The ship fired on the U-boat, illuminated it with snowflakes and managed to ram it just forward of the conning tower, scraping over the hull of the submarine. As the U-boat emerged from under the stern, depth charges set for ''shallow'' were dropped, blowing up the U-boat. The bows of ''Stork'' were crushed and bent sideways and the Asdic dome under the hull was smashed.