White.

AUTHOR’S INTRODUCTION

I first discovered the German Navy at the age of ten, when I had to prepare a project for school work concerning the Second World War. I drew on the experience of a British sailor known to me who gave me an eyewitness account of the Allied landings in Normandy in June 1944. Two years later, now at secondary school, I happened to stumble across my old project notes and became interested in how the German Navy had responded to the Normandy invasion. Thus started a lifelong fascination that had resulted, by my late teens, in the compilation of a huge, hand-written database that contained everything about the Kriegsmarine that I had been able to discover.

After the publication of U-boat Tankers 1941–45 (Airlife/Naval Institute Press) in 1998, I found my interest rekindled in a new area that had been little researched: the ‘New U-boat War’ of 1944–45, particularly as directed against the British east coast.

By the time of the Normandy invasion, the U-boats were a beaten force, hunted and harried wherever they appeared by Allied warships and aircraft that were technologically superior. The U-boats proved to be little more than pin pricks against the landings, and advancing Anglo-American armies had driven them out of their French west Atlantic bases all the way back to Norway by September 1944. Yet the U-boat force mounted a sustained and effective campaign from their Norwegian bases, the ‘New U-boat War’, against Allied merchant shipping from September until the end of the war in May 1945.

The explanation for the reversal of fortunes was the introduction of the schnorchel, a device that allowed the submerged U-boat to ventilate its interior and draw air for the diesels to recharge its batteries. As the U-boat no longer needed to come to the surface, it was much more difficult to detect, and successful aircraft attacks – since 1942 the principal cause of losses to the U-boat arm – dwindled almost to nothing. However, most of the schnorchel-fitted U-boats now lacked the range and endurance to patrol further than the British Isles. Thus the last months of the war saw a final onslaught by schnorchel-fitted U-boats into the shallow waters of Britain’s coastlines, better known today as ‘the Inshore Campaign’.

Although the basic story of the Inshore Campaign has been covered many times in general books about U-boat warfare, I have been unable to discover a single book dedicated to this extremely important topic. Therefore I have provided a substantial background to the Inshore Campaign generally, before focussing on the main subject: the Inshore Campaign off Britain’s east coast. The East Coast Campaign had several unique features, including the presence of extensive minefields, the shallowness of the waters, the importance of army supplies ferried directly from Britain to the Dutch river Scheldt, and the first and only deployment of the new German Type XXIII ‘electric’ U-boats.

Most of the existing accounts of the Inshore Campaign rely on standard British sources and the war diary of U-boat Command. The great majority of the original war diaries of U-boats patrolling from Norway were deliberately destroyed towards the end of the war, or when the commanders surrendered at sea; all on direct orders from U-boat Command. In fact there remain virtually no war diaries from any U-boat on patrol after mid January 1945. Since archived war diaries have survived, it is difficult to avoid the conclusion that the guiding principle was that war diaries should not be archived until they had been vetted for anything that might incriminate senior naval staff after the war, which was now clearly lost.

However, I have managed to reconstruct events with additional information from a painstaking trawl though decrypted wireless messages stored at the British Public Records Office, and by discovery of a very few surviving U-boat war diaries, with the very helpful aid of Kate Tildesley, curator at the Naval Historical Branch, Portsmouth. It is a pleasure also to thank Prof. Juergen Rohwer, Dr. Axel Niestlé and Frans Becker for their valuable and speedy assistance in clearing up some unresolved issues.

John White, Wokingham.

Notes

‘Miles’ always refers to sea-miles.

‘Kristiansand’ in the text always refers to the Norwegian harbour of Kristiansand South, and should not be confused with Kristiansund.

‘zS’ in the text is always an abbreviation for ‘zur See’.

The Germans used ranks equivalent to those in the Royal Navy, as follows:

The Kriegsmarine had divided up all the oceans of the world into a series of grids before the war, as a security measure. Thus references by the Germans to a particular sea area were always made by reference to this grid (e.g. AN7134) and not by the more conventional latitude and longitude measurements. The smallest element of the grid – the ‘4’ in the above example – referred to an area about six miles square, the smallest measurement that could be made accurately by ships or U-boats at sea. The British Admiralty had little difficulty in reconstructing the whole grid system once they had seen a torn part of a captured German map.

The Germans measured fluids, such as fuel, in cubic metres, referred to as ‘cbm’. A cubic metre of water weighs one metric ton, approximately equivalent to a British or American ton. However, fuel and diesel oils are lighter than water, so that one cbm of oil weighs rather less than one ton.

PART I

THE INSHORE CAMPAIGN

June 1944

At the time of the Allied invasions at Normandy on 6 June, the much vaunted U-boat arm was a weakened and defeated force. Long gone were the days of glory when the grey wolves, running at high speed on the surface at night, had emerged from their bomb-proof bases along the west coast of France to terrorise merchant shipping in the Atlantic ocean. The introduction of radar into Allied warships had stopped the night surface attack, and the introduction of radar into Allied aircraft had forced the U-boats underwater, where they crawled around at one or two knots, surfacing only to recharge their batteries. Even this brief period of exposure on the ocean surface at night exposed the U-boats to a severe danger of air attack. Moreover, the happy days when submersible tankers, the so-called ‘milk cows’, could refuel the U-boats so that they could turn their attentions to any sea area across the entire Atlantic had also disappeared. The old U-boat ‘aces’, made famous by German propaganda and high awards (such as the Knights Cross), had by now all died in action, been transferred, or promoted to office jobs. Their successors lacked the same experience and tended to be sunk before they could acquire it. By mid 1944, it was very common for U-boats to be sunk during their first patrol.

Such had been the recent lack of success in the north Atlantic, against the critical Allied convoys bringing valuable war supplies to Britain, and against the empty convoys returning in ballast to the USA for further reinforcements, that Doenitz (head of the U-boat arm and since January 1943 also the Grand Admiral of the entire German Navy) had felt it necessary to withdraw the U-boats from that theatre in March 1944. Most of the shorter-ranged U-boats, the Type VIIs, were now held back in their bomb-proof pens facing the Bay of Biscay, and also in Norway against a feared invasion of that country, to allow a last gambler’s throw against the expected Allied invasion of Europe. The tiny, very short-ranged, Type II ‘canoes’ had been withdrawn long ago to the Baltic, and now were used only for training new crews.

The war against merchant shipping was conducted largely in remote, fairly safe, areas of the ocean by the longer-ranged Type IX boats. Even so, very few were on patrol at any one time. German U-boat strategy at this time was simply to tie down huge numbers of Allied forces, especially aircraft, that might otherwise be deployed against Germany and its occupied territories.

There remained a slight hope against the ever-present air threat. Contemporary submarines of all navies were powered on the surface by diesel engines, which required air (as well as fuel) to operate. Underwater, the submarines were powered by rechargeable giant batteries, rather like modern car batteries. The batteries lost their charge more rapidly at higher speed, so that at a maximum of seven knots, the battery would be discharged within one hour. At an underwater speed of one knot, the battery would provide propulsion for about 24–48 hours. No submarine can hover underwater, it has to keep moving to maintain its depth through use of the hydroplanes. Therefore, once the battery was discharged, the submarine had to return to the surface so that the diesels could be operated, using a gearing system to recharge the batteries.

The Dutch had invented a device, essentially an air tube, which allowed a submerged submarine to ‘breathe’ air while submerged. Thus the air in the boat could be freshened and, especially, the diesel engines could be operated to recharge the batteries needed to power the submarine when it was fully submerged. The Germans had seized the device when they occupied Holland in 1940, and necessity had caused them to conduct trials with U-boats with the air-tube, named a ‘schnorchel’ (a slang name for a long nose). By June 1944 some U-boats had carried out war cruises with schnorchels installed, and this had largely protected them from air attacks. The U-boats no longer needed to return to the surface to recharge their batteries.

The schnorchel was certainly not a cure-all. The float-head which kept the end of the air-tube above water had a valve that shut off the intake of air whenever the schnorchel dipped below the tossing sea. This caused a sudden loss of air within the U-boat as the diesel engines momentarily tried to suck in air from within the U-boat, before the engines were temporarily stopped. In addition, the float-head often jammed or failed to function properly. Thus the crews of schnorchelling U-boats were constantly forced to gasp for breath and suffer their ears to pop as the internal pressure fell steeply. On the other hand, diesel and combustion fumes were often forced into the U-boat, resulting in a real risk of poisoning from carbon monoxide gas.

The schnorchel had other defects too. It was so bulky, and therefore easy to spot when the U-boat was at periscope depth, that it had to be raised upright by a hydraulic or line system when required. This system sometimes failed, so that a U-boat might find that it could not schnorchel at all (device jammed in lowered position), or that any attack at periscope depth was compromised by the presence of a large prominent globular device perched on top of a thick stalk next to the tiny periscope (device jammed in raised position). Another serious problem was that in use the schnorchel blew out clouds of gas, fumes and steam, visible from miles away. Therefore schnorchelling was carried out at night. A submerged, schnorchelling U-boat could not tell if an aircraft was approaching, and Allied air-borne radar was now sufficiently precise to pick out the large schnorchel head on the sea. This ability of Allied air-borne radar was known to U-boat Command before 10 September, and U-boats were ordered to lower the schnorchel as far as possible while it still functioned. The Germans experimented with various synthetic anti-radar coverings for the schnorchel head, but the most effective procedure was simply to place a radar detector on the head. When it picked up a closing Allied bomber using radar at night, the U-boat had only to lower the schnorchel to avoid detection. The schnorchel-mounted radar aerial could detect short wavelength radar at a range of only one kilometre (about half a mile; much further for medium wavelengths), but this proved to be sufficient in practice when coupled with the deadening effect of the anti-radar covering ‘Tarnmatte’ for the schnorchel. A more sensitive radar receiving aerial was in development at war’s end.

Since the U-boat no longer came to the surface, it was impossible to throw overboard the accumulation of rotting food waste. Eventually one enterprising (or long-suffering) commander decided to push all the rubbish into a torpedo tube, which would be ‘fired’ with compressed air periodically. This solution became widely adopted, but meant that one of only five torpedo tubes in the boat was inoperable for long periods. Yet another problem with schnorchelling was that the clatter of the diesels drowned out all sound around, so that the crew could not detect on their hydrophones the propeller sounds of a closing Allied warship. The procedure was to stop the diesels every twenty minutes, in order to allow the soundman to listen carefully. The U-boat could only move at about five knots while using the schnorchel, since there was a danger that it would snap off at higher speeds. Generally speaking, then, the schnorchel was extremely unpopular with U-boat crews, many of whom preferred to come to the surface and risk the air menace.

Schnorchel-fitted Type VII U-boats had