This is the story of a convoy – just one of hundreds that put to sea during the war. Britain was wholly dependent on merchant shipping to import the foodstuffs and raw materials it needed. This shipping was the lifeblood of the British war effort. A convoy system was introduced to protect this vital maritime lifeline, but losses mounted alarmingly as the ferocity of U-boat attacks increased. By late 1941 it was clear that the U-boats had the upper hand. Merchant ship losses greatly surpassed the number of new ships built. If the situation continued, Britain would literally be starved into submission. HG-76, though, was different. It represented the first real attempt to challenge the U-boats’ dominance. At stake was Britain’s very survival.

Although I knew about the Battle of the Atlantic, I have to admit that I hadn’t heard of HG-76 until a few years ago. That changed when I stumbled across an article in Battlefleet, a naval wargaming journal, written by Australian naval historian Mal Wright. His well-researched piece highlighted the importance of HG-76 in the greater scheme of things. On reading it I realized I could use the Convoy HG-76 story as a way to explain the Battle of the Atlantic, by focusing on just one of those hundreds of convoys, seen through the eyes of those who sailed in it. That then became the inspiration and starting point for what became an absorbing voyage.

The more I looked into it the more intrigued I became. First of all, HG-76 was markedly different from previous convoys. Not only was HG-76 protected by a large escort group, but the escort commander was Commander Johnnie Walker – a man who would carve his name in the history books as Britain’s leading U-boat hunter. In December 1941, though, he was a hero whose time was still to come. Until then, the British Admiralty had rejected his novel ideas on anti-submarine tactics, and had ignored his pleas to demonstrate them. This would be Walker’s moment – his chance to shine. His success in defending HG-76 finally forced the Admiralty to listen to him. Walker would become a household name, and his methods, first perfected during the battle for HG-76, would become standard practice among the Allied navies.

The other big advantage the convoy had was Audacity. She was the Royal Navy’s prototype escort carrier – a completely new type of warship, created to carry out a unique job. Until now, U-boats had had little to fear from aircraft, once the convoys they hunted moved out of range of land-based planes. Aircraft carriers were simply too valuable to use for convoy work. The escort carrier was designed to solve that problem. These miniature carriers were designed to accompany convoys, and provide them with both fighter cover and a means of detecting U-boats from the air. Audacity would be the first of them, and like Walker and his methods, HG-76 would be the ‘make or break’ proving ground for them.

Although Audacity did not survive the convoy battle, she more than exceeded the Admiralty’s expectations. After HG-76 the Admiralty understood the escort carriers’ value and these little carriers would become a vital tool in the war against the U-boats. One of Audacity’s pilots was Sub Lieutenant Eric ‘Winkle’ Brown. He would go on to become the Navy’s leading test pilot of the jet age. Again, while I’d heard of ‘Winkle’, I didn’t know very much about him. However, Eachan Hardie, the teenage son of good family friends, was fascinated by the pilot. Through conversations with him my interest in ‘Winkle’ was piqued. So, the ‘Winkle’ angle became another catalyst for this book.

As I researched HG-76, I realized just how special it was. First of all, Walker’s escort tactics proved a real battle winner in the war against Hitler’s U-boats. Having been given command of the convoy’s escorts, Walker and his men went on to sink four U-boats in five days. For the first time in the U-boat war the Germans had a real fight on their hands. Audacity was a major game-changer as well, but it was Walker who tied everything together. It was his job to protect the convoy, and everything that followed had Walker’s distinct stamp on it.

The Germans, too, were out for a fight. A few weeks before, Hitler had ordered Vizeadmiral Karl Dönitz, his U-boat chief, to concentrate on severing the sea route between Britain and Gibraltar. So, whereas earlier ‘Gibraltar Run’ convoys had attracted little attention, a whole wolfpack was sent out to attack HG-76. The wolfpack was an ad hoc concentration of boats, used against a particular convoy. Until then, the wolfpacks had enjoyed considerable success in the Battle of the Atlantic. This time it would be different. After suffering heavy losses at Walker’s hands, Dönitz eventually called off the attack. For once the defenders had won the convoy battle, and done so convincingly. Although more gruelling convoy encounters lay ahead, not only did the Allies now know that the U-boats could be beaten, but the Admiralty knew just how to do it. This, more than anything, is what made the HG-76 convoy a key moment in the war against Hitler’s U-boats.

Several years ago I collaborated with the U-boat historian Jak Mallmann Showell to produce a small book about a U-boat flotilla. So, I knew something about the available German sources. Since then, though, thanks to the internet, there has been an explosion in the availability of German material. As a historian, I now had much more information at my fingertips than ever before. The same is true of the British side, where new avenues of research had become available. From websites on Norwegian merchant ships to online archives of personal reminiscences, these were all waiting for me to tap into them, to help tell the story.

This, then, was another driving force for this book. For the men involved in the battle for HG-76, this was a defining moment of their lives. The survivors – at least those who wrote about their experience – have offered us the chance to share these dramatic events through their eyes. Today, although the number of these survivors left alive has dwindled away, their stories can still be told through their written and spoken words. If as a historian I can capture something of the tension, fear and drama of the events they described, then this book has achieved its purpose.

Until now their dramatic story, and the tale of Convoy HG-76 hasn’t been fully told. This was a real game-changer in the U-boat war, but at the time this wasn’t fully appreciated, and these events never really earned the attention they deserved. After all, the Japanese attack on Pearl Harbor helped see to that, as even more momentous events were unfolding on the far side of the world. Now, though, the time has come to look afresh at this half-forgotten convoy that represented such a distinct turn in the tide of war. Thanks to Walker and his escorts, and the fighter pilots of Audacity, HG-76 can today be remembered as the convoy that fought back.

If you enjoyed today's extract you can read more in The Convoy: HG-76: Taking the Fight to Hitler's U-boats.