Battle of the Atlantic

Marc Milner

• Publisher: The History Press
• Year: 2011
• Print ISBN: 9780752461878
• eBook ISBN: 9780752466460
• Topic: History
• Subtopic: Military & Maritime History
• Index: History

World War II was only a few hours old when the Battle of the Atlantic, the longest campaign of the Second World War and the most complex submarine war in history, began with the sinking of the unarmed passenger liner Athenia by the German submarine U30. Based on the mastery of the latest research and written from a mid-Atlantic – rather than the traditional Anglo-centric – perspective, Marc Milner focuses on the confrontation between opposing forces and the attacks on Allied shipping that lay at the heart of the six-year struggle. Against the backdrop of the battle for the Atlantic lifeline he charts the fascinating development of U-boats and the techniques used by the Allies to suppress and destroy these stealth weapons.

1

Opening Skirmishes

September 1939–March 1940

Within hours of the sinking of Athenia, the Royal Navy began its system of convoys, and deployed forces to stop German trade, intercept raiders and sink U-boats. German merchant vessels were harried at sea, some were sunk or captured, but the German surface raider fleet proved to be remarkably resilient. Kriegsmarine battlecruisers and pocket battleships struck into the broad ocean with comparative impunity. Although their success against Allied merchant vessels was slight, only one German raider was hunted down and destroyed in these early months. The others seemed to come and go as they pleased, and the lingering threat from a powerful and growing German battlefleet remained the primary concern of the British Admiralty. None of this was helped by the fact that the initial British anti-submarine offensive was a catastrophic failure.

In fact, the first month of war indicated that the submarine remained a very effective weapon. Of the fifty-three Allied vessels sunk by the end of September, forty-one were claimed by U-boats, and of the remainder most fell to mines, many of which were submarine-laid. In exchange, two U-boats were lost. British attempts to find and sink U-boats with hunting groups and aircraft were tragically futile. The first RAF Coastal Command aircraft to attack a sub in September 1939 crashed when its own anti-submarine bombs skipped on the water and exploded under the aircraft. The sub, which happened to be British in any event, escaped unharmed. Meanwhile, the Royal Navy began deploying its aircraft carriers into the Atlantic to hunt and sink U-boats. It proved a poor idea. On 14 September, U-39 fired a spread of three torpedoes at the aircraft carrier Ark Royal, which was on anti-submarine patrol west of Ireland. The torpedoes narrowly missed. U-39 was promptly sunk by the carrier’s escorting destroyers, which also rescued the submarine’s crew. It was the first U-boat kill of the war. But U-39 was an exception, one of only two U-boats found and destroyed by British hunting forces in the first six months of the war. The kill was also a stroke of luck. Shortly after U-39 was despatched, two Skua dive-bombers from Ark Royal located U-30 and attacked it with anti-submarine bombs. These bombs – like those dropped by RAF aircraft earlier in the month – also skipped on the surface, detonated in the air and brought both attacking aircraft down. The Skua’s crews were rescued by the U-boat; surely one of the most bizarre episodes of the war.

The British were not so lucky with the second aircraft carrier sent to hunt U-boats west of Ireland in September. When HMS Courageous suddenly altered course to retrieve her aircraft late in the afternoon of 17 September, she turned right in front of U-29 at a range of only 3,000 yards. Two of three torpedoes hit, sending the carrier to the bottom in fifteen minutes with heavy loss of life. Courageous’ escort hunted the U-boat without success and Kapitänleutnant Otto Schuhart arrived home to a hero’s welcome. No more fleet class carriers were sent to hunt submarines. The British had the right idea, but the best carrier for anti-submarine operations proved to be small – and expendable – and aircraft needed much better weaponry. Not surprisingly, the Flag Officer for U-boats, Commodore Karl Dönitz, reported optimistically on 28 September that, ‘It is not true that Britain possesses the means to eliminate the U-boat menace… Enemy technique has doubtless improved, but so has the U-boat, which now moves more silently.’

To prove his case, Dönitz ordered U-47, commanded by Günther Prien, to raid the main British fleet anchorage at Scapa Flow. In one of the most memorable feats of wartime navigation and skill, Prien slipped silently into the anchorage on the night of 13 October and attacked the battleship Royal Oak as she rode quietly at her mooring. Approaching on the surface, Prien fired all four torpedoes from his bow tubes at a range of only 4,000 yards. One failed to leave the tube, two missed the target, and one struck either the bow of the battleship or its mooring cable. The detonation occasioned surprisingly little alarm. Royal Oak’s officers concluded that the detonation was some kind of internal explosion. Meanwhile, Prien swung U-47 around and fired his stern tube: that torpedo failed to hit. Stunned by his inability to hit a huge stationary target at point blank range, Prien waited patiently for the next twenty minutes while his crew frantically reloaded the forward tubes. Then, at 01:16 hours, he fired another spread of three torpedoes: all of them hit. ‘Over there a curtain of water rises,’ Prien wrote afterwards. ‘It is as if the sea is suddenly standing up. Dull thumps sound rapidly in succession, like an artillery barrage in a battle, and grow together into a single ear-splitting crash – bursts of flame spring up, blue, yellow, red….Black shadows fly like giant birds through the flames… Fountains metres high spring up where they fall. They are huge fragments from the masts, the bridge, the funnels. We must have made a direct hit on the magazine…’ And so he had. Nearly 900 men perished aboard Royal Oak, and the vulnerability of the fleet was exposed. Prien received a hero’s welcome, and even the British had to admit his penetration of the Home Fleet anchorage and the attack on Royal Oak was a remarkable accomplishment.

But the Atlantic war was not about sinking carriers and battleships, it was about sinking the humble merchant vessels that carried the sinews of war. In that respect, German prospects were not entirely rosy in the late summer of 1939, and the foundations of the solid organisation that would ultimately defeat the German war at sea were being laid. In fact, the war began about five years too early for the German navy, which hoped to be in a position to challenge British sea power directly by 1944 or 1945. With the limited resources available in 1939, Grand Admiral Erich Raeder, head of the Kriegsmarine, chose a strategy of disruption against the Allies. Operations were aimed primarily at Allied merchant shipping in the hopes that they might occasion delay and embarrassment to Allied plans, and perhaps even stop some operations. Raeder was under no illusions that against the combined might of the French and the British, the Germans could achieve much. Indeed, as he confessed in his memoirs, the best that the German navy could do in 1939 was to ‘show that they knew how to die gallantly’.

Many did. In the early stages of the war, Anglo-French sea power dominated the surface of the world’s oceans and made fugitives of German raiders or confined them to more remote seas. Of the two major warships deployed in August 1939, the pocket battleship Graf Spee was tracked down and forced into an ignominious scuttling on a sand bar in the River Plate off Uruguay in December following a classic gunnery battle with three British cruisers. She might well have escaped but for an ill-conceived decision by her captain to fight when cornered. Graf Spee’s supporting tanker, the Altmark, was tracked and finally trapped in a Norwegian fjord in February, where by international law the ship ought to have been immune from attack. But the British government ordered the destroyer Cossack to take off the 299 British seamen prisoners she carried. The scuttling of the Graf Spee and the boarding of the Altmark ‘caught the imagination of the British people’, the Royal Navy’s official historian wrote later, and ‘showed that once again the Germans could not challenge us on the seas with impunity…’.

The other pocket battleship, Deutschland, made it home safely with little to show for her efforts. In the last four months of 1939, cruises by major warships – including the first by the new battle-cruisers Scharnhorst and Gneisenau, and a sortie by the pocket battleship Scheer – accounted for only fifteen Allied vessels, and sank only seventeen during the whole of 1940. But the British did not have it all their way. When Scharnhorst and Gneisenau tried to slip into the North Atlantic in November through the Faeroes-Iceland gap, they stumbled on the 16,700-ton armed merchant cruiser Rawalpindi, which was on patrol and supported by heavier vessels nearby. Rawalpindi answered the German summons to ‘heave to’ with gunfire, smoke and a radio transmission calling for help. But no help could arrive during the fifteen minutes it took the two battlecruisers to pound the old liner into a wreck. Then, for the next two hours, the German ships engaged in rescue work, the only time during the war large raiders were afforded that luxury in the North Atlantic. The effort was only given up when, in the light from the burning hulk of Rawalpindi, the Germans sighted a shadow cast by the light cruiser Newcastle. Her guns were no match for Scharnhorst and Gneisenau either, but her torpedoes, delivered at close range in the dark, were, and so the powerful German raiders beat a hasty retreat.

The direct impact of major German warships on the war against shipping remained negligible: by 1945 only forty-seven Allied ships had been lost to the guns of battleships and cruisers – about the same number were lost to mines during any three-month period during the war. It is easy to dismiss this raiding effort by capital ships as ineffective and rather pointless, but it tied down huge Allied naval and air forces, and did so until nearly the end of the war. Large units of the German fleet could not be ignored and they proved remarkably difficult to destroy. Scharnhorst, Gneisenau, Scheer, Lutzow (the renamed Deutschland) and the heavy cruiser Prinz Eugen all operated in the Atlantic without fatal interception. Indeed, in early 1941 Scharnhorst and Gneisenau cruised to the Grand Banks of Newfoundland, raiding shipping where Scheer had attacked a convoy weeks earlier and sank the small armed merchant cruiser Jervis Bay. Only Bismarck – the last to sortie into the Atlantic in May 1941 and unlucky as well – was actually caught in the noose and sunk. It is important to bear in mind this ongoing struggle with powerful German surface ships when the focus of the war at sea shifted to submarines.

Added to the problem of a small but modern and highly efficient German surface navy was that of their equally small – consisting of only some seven vessels – fleet of disguised merchant raiders. These regular trading vessels had been refitted as auxiliary warships, manned by naval crews and prepared with a number of disguises to cruise the distant oceans of the world and attack unwary Allied shipping. In 1940, their first and best year of operations, such raiders acco-unted for fifty-four Allied vessels, many of these in the southern ocean where Atlantis, Kormoran and Penguin made reputations as particularly effective raiders. For the Allies, the elimination of these marauders, and indeed the interception and destruction of major warships, depended upon the power of the main fleet, good luck of patrols, and, equally importantly, on the progressive expansion of the British Commonwealth’s system of naval intelligence and naval control of shipping.

The bedrock of the whole system of trade defence in the North Atlantic was the British Home Fleet. Its superior force of battleships, aircraft carriers, cruisers and destroyers checked the main power of the German navy and made it a fugitive presence at sea. This had been understood clearly by the Admiralty in the inter-war years. Battlefleets could not be improvised in times of crisis, as the smaller escorts of the anti-submarine fleet could. So the limited inter-war budgets had been wisely spent.

Naturally, it would have been best for the British to destroy the Kriegsmarine battlefleet outright early in the war, thus freeing men and materiel for other duties. But the Germans understood this perfectly well, and there was little to be gained by being crushed in a gunnery duel with the Royal Navy. With a small but modern force it made sense to maintain a fleet in being, to probe and upset defences, to spread them thin, and force the British to be strong everywhere. It was a logical and effective strategy. By October 1939, the British had four battleships and battlecruisers, thirteen cruisers and five aircraft carriers chasing raiders in the Atlantic, and four battleships and battlecruisers, two cruisers and a carrier assigned to convoy escort in the North Atlantic. All this in response to the two pocket battleships, Deutschland and Graf Spee. Meanwhile, patrols maintained by the powerful French navy secured convoys operating southward, towards Africa and the Mediterranean.

Naval stations, intelligence centres and sub centres.

For the Allies, the second crucial component to securing the North Atlantic was therefore sound naval intelligence. This allowed enemy forces to be tracked, against the backdrop of known Allied warship and merchant vessel movements, and fleet units to be deployed to intercept them or to screen shipping. Gathering intelligence included not only keeping watch on major naval units, like Scheer or Bismarck, but also trying to track everything that moved. By keeping track of all the pieces of the puzzle, it was easier for patrols to know if the vessel they had in sight was what it claimed to be, or if it was a raider in disguise. In one of the most remarkable incidents of the war, the raider Kormoran maintained her disguise long enough to entice the Australian light cruiser Sydney to within 900 yards – a fatal error in judgement – when that warship stopped her on 19 November 1941 in the Indian Ocean. While the crew of Sydney tried to figure out just whom they were dealing with, Kormoran unmasked her guns, shattered Sydney with the first salvoes and put at least one torpedo into her. The burning cruiser was last seen drifting away over the horizon while the Germans aboard Kormoran fought their own fires and steamed for the Australian coast. Most of the Germans were later rescued; Sydney and her crew were never seen again. Naval intelligence was, therefore, crucial, and British Commonwealth naval intelligence began tracking the movements of potential merchant raiders – ships which had strengthened decks to take guns in times of war – as early as 1934, when they began to track Japanese vessels. That attention was extended to potential German raiders in September of 1938, and to similar Italian ships in February 1939. It was essential for operational naval forces to know where the enemy was so he could be attacked, but such intelligence was also crucial for diverting merchant shipping away from danger areas. Basic avoidance of the enemy remained, in fact, the principal means of defending shipping during the Second World War.

In order to make the most of covering actions by the fleet and information provided by naval intelligence, it was necessary that merchant shipping be brought under some form of effective control, what was known as ‘Naval Control of Shipping’ (NCS). Eventually the NCS organisation tracked the movements, cargoes and destinations of, eventually, all Allied merchant shipping. Working in conjunction with naval intelligence, NCS organised convoys, controlled the movements of independently routed shipping, co-ordinated departures with operational forces, and worked closely with civilian agencies, shipping firms and economic and transportation ministries to keep the ships moving. This global system had been maintained between the wars and was in good running order in 1939. Information moved around the globe via secure underwater telegraph cables through an information exchange known as the VESCA system. Daily summaries of local movements were passed to the central plots in London, and to and from local naval intelligence and NCS regions around the world. With assigned routes given out to merchant captains and convoys it was, in theory, possible to know exactly where everything was at any given time on any given day. Even safe routes for neutral shipping were promulgated. During the war, the NCS system worked well enough to route most shipping away from most dangers, and to help track down German merchant raiders as well.

It is because of this complex and effective system of trade defence that the German submariners reported in late September 1939 that a large proportion of shipping was already sailing in convoys, well screened by destroyers and in some cases cruisers, and well supported inshore by aircraft. This was not unexpected by the Germans, and Commodore Karl Dönitz had developed an operational and tactical scheme for finding and attacking them. The solution was to operate U-boats in groups, deploying them in a line across the path of the convoys to ensure interception, and then attacking the convoys on the surface at night, using the U-boats like motor-torpedo boats, slipping in on the surface at high speed and using the same high speed or submergence to escape the escort following the attack.

In response to the early introduction of escorted convoys around Great Britain, Dönitz launched the first pack operation in early October 1939. Six U-boats were ordered to concentrate south of Ireland and work as a pack to attack convoys. Kapitänleutnant W. Hartmann in U-37 was designated as tactical commander of the group. As things turned out, three of the group failed to make the rendezvous. U-40 took the shortcut through the English Channel and paid for its audacity when it was sunk by a mine off Dover. U-42 and U-45 fared no better: both were sunk by escort vessels of convoys while en route to the rendezvous. That left Hartmann with only his own submarine, plus U-46 and U-48. Undaunted, on 17 October the tiny group launched an operation against the homeward-bound convoy HG 3 while it was still well out to sea and still unescorted. The attacks were plagued by torpedo failures, but each U-boat claimed one vessel before air support arrived to drive them off. From the German perspective the assault on HG 3, which warrants no notice in British accounts, was a qualified success: proof of the basic concept of pack attacks on convoys. But for the moment, there was little point in trying to attack convoys. After the ‘battle’ for HG 3, Hartmann went on to sink seven independently routed ships during the rest of his autumn 1939 cruise.

The second pack operation, launched in November, was less successful. It, too, had difficulty getting the designated U-boats to the rendezvous when two of the five were reassigned, leaving only three for operations. More significantly, strong naval and air escorts and torpedo failures hampered attacks on both French and British convoys in the South Western Approaches. And again the U-boats of the pack had their greatest success sinking stragglers and independents. Given the difficulty of organising packs from such a small U-boat fleet and the constant distraction of easy targets, attempts to launch pack operations were temporarily abandoned in November 1939.

The abandonment of pack operations in late autumn 1939 meant that convoys enjoyed something of a false sense of security in the first phase of the war. From the submariner’s perspective, there was little point in attacking escorted convoys while the ocean remained full of independently routed shipping. In fact, while all Allied merchant shipping immediately came under effective control of the NCS in 1939, it was not until 1943 that the majority of Allied shipping worldwide moved in ...

Table of contents

• Cover
• Title
• Contents
• Preface to the Second Edition
• Introduction
• 1 Opening Skirmishes
• 2 The Battle of the Atlantic Begins
• 3 The Allies Strike Back
• 4 Carnage off America
• 5 Mid-Atlantic Confrontation
• 6 Crushing the Wolf Packs
• 7 Driving the U-Boat Down
• 8 Troubled Waters
• 9 Defeating the Old U-Boats… Again!
• 10 The Crisis that Never Was
• Afterword and Acknowledgements
• List of Abbreviations
• Bibliography
• List of Maps and Diagrams
• Copyright