At 4pm on Sunday 14 December 1941, the homeward-bound Convoy HG-76 began leaving Gibraltar Bay. By 5.30pm it was heading west into the Atlantic at 7 ½ knots, at the start of its 2,000 mile voyage to Liverpool. Its 32 merchant ships were formed up into a neat rectangle of ships, some four miles across and a mile deep. It would stay in this formation until it reached port. Carried in the holds of these merchantmen were all the things that Britain needed to stay in the fight,  everything from iron ore to Spanish onions. It was just one of hundreds of similar wartime convoys. However, three things made HG-76 a little special.

First of all, it been singled out for special attention by Vizeadmiral Dönitz, commander of Hitler’s U-boat fleet. On Hitler’s orders, Dönitz had diverted U-boats from the transatlantic convoy routes to concentrate on the Gibraltar convoys. Wolfpack Seeräuber (“Pirate”) was being assembled with orders to attack the convoy as it headed north. Thanks to Enigma intercepts though, the British knew about this, and so HG-76 was particularly well-defended. No fewer than 17 escort vessels protected the convoy, although most of these wouldn’t remain with it for the whole voyage. These escorts ranged from the lend lease destroyer HMS Stanley to much smaller and humbler corvettes.

Commander Walker

Convoy HG-76 though, had two very important advantages. The first of these was the man commanding the convoy escorts. Commander Frederic “Johnnie” Walker RN was a specialist in anti-submarine warfare, but until then his radical ideas for hunting U-boats had been largely ignored by the Admiralty. The mere passive defence of a convoy wasn’t enough for him. He felt the best way of defending a convoy was to destroy the U-boats which threatened it. It was a radical idea, as the official doctrine emphasised the protection of the convoy over rathe than the destruction of the enemy. Walker’s tactics also needed a strong escort force, and until this stage of the war there simply weren’t enough escorts to adequately protect a convoy, let alone deliberately seek out the enemy. Now though, with HG-76, Walker finally had the chance to show just how effective his tactics could be.

Essentially, when a U-boat was detected, then a group of escorts would be detached to hunt for it. Where before, it was often up to left to a single escort to attack a U-boat, Walker now saw the task as a team effort. His methods emphasised teamwork and perseverance. Submerged U-boats were detected using Asdic – later called sonar, using a sound pulse which bounced back off any underwater contact. The trouble was, when a contact was made, and an escort tried to attack it, there was a “dead time”, for perhaps half a minute when contact was lost, as the escort passed over the U-boat. That gave the U-boat skipper time to evade the attack. Walker solved this problem by operating in groups. Once contact was made, one escort would track the target using Asdic. The others would take turns to attack the target, after the tracking vessels guided them over the target using their radio.

It was simple but effective. There was still another problem though. At that stage of the war Asdic couldn’t tell what depth the U-boat was at. So the depth charges could explode above or below the target. Walker solved that problem by having them conduct multiple attacks, with patterns set at different depths. This then, greatly increased the chances of destroying the U-boat. Teamwork, communications and training were needed to make this all work. That though, is exactly what Walker developed among the vessels of his 34th Escort Group. Then, when they were reinforced for the protection of HG-76, Walker made sure these new crews knew exactly what he expected of them. Walker was also able to take advantage of the second big advantage – HMS Audacity. She was the Royal Navy’s prototype auxiliary carrier – soon to be renamed the escort carrier. Her job was to detect U-boats on the surface,  and to drive off shadowing reconnaissance aircraft. Although Audacity only carried four Martlet fighters, this little carrier and her aircraft soon proved invaluable.

U-boats could only intercept a convoy on the surface, as once submerged they were too slow to keep up with it. So, Audacity’s fighters flew regular sweeps around the convoy, and often managed to spot these shadowing U-boats. Then, Walker would send out escorts to attack the U-boat. Their first success came on 17 December, when U-131 was sunk after being sighted by a Martlet 22 miles away from the convoy. This feat would be repeated the following day, when U-434 was sunk.  Audacity though, was torpedoed and sunk late on 21 December. By then though, she had shown just how useful an auxiliary carrier could be.  Afterwards, the Admiralty would commission dozens of new escort carriers – improved versions of Audacity. The escort carrier would go on to play a key part in the war against the U-boats.

So too would Commander Walker. By the time HG-76 reached Liverpool on 29 December it had only lost two merchant ships, an impressively low number for the period. In return, Walker had sunk four U-boats, which was a hitherto unimaginable success rate for a convoy. Walker was duly promoted, but he remained at sea, continuing the fight against the U-boats until his untimely death in 1944. After HG-76 though, he was finally listened to, and soon his aggressive tactics were officially adopted by the Royal Navy, and by many of their Allies. After the war, “Johnnie” Walker would be recognised as Britain’s most successful U-boat hunter. HG-76 then, marked a real turning point in the hard-fought Battle of the Atlantic. It showed the Allies how they could turn the tide, how they could successfully take the fight to Hitler’s U-boats, and then how they could defeat them. The rest, as they say, is history.

Angus Konstam is a historian and the author of The Convoy: HG76 – Taking the Fight to Hitler’s U-Boats, published by Osprey.