4
Science Goes to Sea
Do you really believe that the sciences would
ever have originated and grown if the way had not been
prepared by magicians, alchemists,
astrologers and witches …
Friedrich Wilhelm Nietzsche
In the opening days of the war, the German magnetic mine gave the Royal Navy one of its first big shocks. It was a simple weapon, but the method of its activation demonstrated some of the curiosities of the natural world. The mines sat on the sea bed and came to the surface to explode against the hulls of ships that passed over them. Inside each mine there was a ‘dip needle’ which was pushed down by the ‘downwards north pole’ of the ship passing over it. Such mines were activated only by ships built in the northern hemisphere. Ships built south of the equator had a ‘downwards south pole’ which pulled the contacts further apart, so they could pass quite safely over magnetic mines.
In fact it was more complex than that: the magnetism of a ship’s hull was not simply north or south. Each ship was different. The hulls varied according to the direction, relative to magnetic north, in which the ship’s keel had been laid down when built. Even more surprisingly, it was discovered that ships sailing to the southern hemisphere and back again changed their ‘magnetic signature’. Prefabricated ships were sometimes assembled from two halves made in different places; the halves then had different magnetic properties. Once a ship’s signature was known, it could be demagnetized by means of a fluxmeter. When the threat of the magnetic mine was suddenly understood, Britain’s only manufacturer of fluxmeters was asked to supply 500 on a rush order; before that only a dozen had been made since 1898.
By their nature these ‘influence mines’ were restricted to use in shallow water, the type TMB in 15 fathoms and the TMC no deeper than 20 fathoms. Smaller mines could be laid through the U-boat’s torpedo tubes; three of them together were about the length of a torpedo. Laid by U-boats or parachuted from low-flying aircraft into harbours, estuaries and coastal sea routes, the German mines caused consternation. The battleship HMS Nelson and the cruiser HMS Belfast were seriously damaged by mines, three destroyers were sunk and so were 129 merchant ships. The Thames Estuary became so littered with German mines that there was talk of closing down the Port of London.
It seemed at first as if it was a problem easily solved, since the Royal Navy had used magnetic mines in 1917. In the interwar years Admiralty scientists had experimented with the magnetic properties of ships’ hulls, but the emphasis was upon counter-measures to the magnetic torpedo. This meant a powerful magnetism that would prematurely explode a torpedo as it approached. But scientists and technicians were few in number and their work was overruled by officials at the Admiralty who thought that mines, like submarines, were weapons for inferior naval powers. Dusting off their old research, the navy tried it out. But they found that magnetic sweeps that countered British magnetic mines exploded German ones. The sweeping devices were often destroyed and sometimes mine-sweepers were badly damaged.
The night of 22/23 November 19391 was dark and moonless. Between 9 and 10 pm a Heinkel He 111, following the Thames Estuary, flew very low over the tip of Southend pier. It was a good landmark: probably Luftwaffe crews were briefed to use the pier as a navigating fix. A machine-gun team at the pier’s far end opened fire and saw two parachutes fall from the plane. Startled by the unexpected gunfire, the Germans had dropped two mines into the shallow tidal water. Its load lightened, the Heinkel sped away.
The report that men had jumped out of the aircraft was discounted. Before midnight, Churchill was told that there was probably going to be a chance to examine the new weapon. By 1.30 am on that same night two experts briefed by Churchill, and the first sea lord, were on their way by car to Shoeburyness, where the mines were exposed by the outgoing tide. By 4 am – with rain falling heavily – the investigating team was out on the exposed mud-flats. Using a powerful portable signal lamp, they were looking at a black aluminium cylinder, seven feet in length and about two feet in diameter. Before anything much could be done, beyond securing the mines, the incoming tide had swallowed them out of reach until the following afternoon.2
Next day steel-nerved technicians from HMS Vernon (the RN’s mine school) defused the weapon. By a stroke of fortune, a mechanical device to keep the mine safe until it had settled on the seabed had jammed. It was actuated by the technicians rolling the mine over but by that time the mechanism had been rendered safe. Stripped of its detonators and priming charges the mine was taken for examination to a ‘non-magnetic laboratory’. In a matter of hours the new weapon was understood: it operated on a vertical magnetic field and required about 50 milligauss to fire it. The threat remained.
When, on Saturday morning, Rear-Admiral W. F. Wake Walker told government scientist Frederick Brundett about the capture of the mine and that he would need twelve engineers by Monday morning, Brundett drove to the south coast to seek out individually men with special engineering skills and sign them up on the spot. One whom he considered essential was already being paid £2,000 a year. ‘As it happened the Director of Scientific Research at the time was only getting about £1,700 a year, and I was subsequently told by the Treasury that I couldn’t do it. I pointed out that I’d already done it and that he was in fact already working for us.’3
Some anti-mine experiments were performed by sailors who towed toy ships backwards and forwards over cables in ‘canoe lake’, a children’s boating pool in Southsea, near to HMS Vernon. Various counter-measures were devised and put into operation immediately. These included ‘de-gaussing’, which neutralized the vertical magnetism of a ship. The mines could be swept by floating electrical cables (through which a current pulsed) behind a de-gaussed ship. Large coils were also installed in low-flying aircraft as a quick way to neutralize minefields.
Such measures were not enough to solve the problem completely. Channels swept by aircraft were narrow and unmarked. The German aviators were bold: one minelaying seaplane landed in Harwich harbour, carefully placed its mines, and then took off again. It was the minelaying operations of low-flying aircraft that led to the construction of new radar stations with apparatus designed for low-level detection. When the Battle of Britain began, these stations were to play a vitally important part in detecting low-flying formations that would otherwise have got in under the radar screen.
The de-gaussing that all British warships were given at this time probably saved some of them from attack by magnetic torpedoes, notably during the Norwegian campaign. At the time these failures were considered to be due to faults in German torpedoes, and no one can be sure of what exactly happened inside the warheads.
The Germans hit upon the idea of sowing mixed minefields with both magnetic and moored mines. These required tricky sweeping techniques. They reversed polarity to catch ships that had been ‘over-de-gaussed’. Delayed-action fuses kept the mines inactive for a period; thus sweeping would be without result.
Then came acoustic mines, which had to be swept with noisy ‘hammer boxes’. There were double fuses that would work only when two triggers were activated, such as noise and polarity. But by the summer of 1940 the magnetic mine had ceased to be a real danger.
On 7 May 1940 a new threat arose. A modified version of the BM 1000, intended as a sea mine in the Clyde, overshot and landed on the Clydeside hills near Dumbarton. These ingenious dual-purpose ‘bomb mines’ were fitted with Rheinmetall inertia fuses when used against land targets. Falling into water at least 24 feet deep they functioned as a magnetic mine; on soft mud or in shallow water they would self-destruct. They would also self-destruct (by means of a hydrostatic valve) when the water pressure lessened, as it would when they were lifted to the surface. It was an example of German thoroughness that, despite all the foregoing precautions, the BM 1000 also incorporated one of the most cunning booby traps ever built. A set of photo-electric cells connected to a detonator would explode the bomb if light got inside it. This was a way of killing any bomb team who got to see the workings. By amazing luck, the bomb found at Dumbarton had suffered a circuit failure.4
A few months later this sort of bomb-mine was extensively used during the night bombing of London. They parachuted down and caused widespread destruction without forming a crater. Londoners found it easy to recognize the results and called them ‘land mines’.
The menace of the magnetic mine had been overcome by the scientists, and this was the important fact. Before the war the admirals and generals in Whitehall had showed little interest in science and technology, but success with the magnetic mine changed that attitude. According to Dr C. F. Goodeve, who was a physicist and RNVR officer: ‘it was the first technical battle in which we won a decisive victory over the enemy; but more important still, it was one which brought science fully into the war in the very early days’.5
In Germany the Nazis had broken with the nineteenth-and early twentieth-century tradition of political encouragement and social respect for science and its practitioners, and there was little or no collaboration between the scientists and the military until the end of 1943, when German scientists were invited to help with the Battle of the Atlantic. Even then they were simply asked to identify Allied radio and radar transmissions.
But Nazi distrust of science and top-level obstruction of research did not change the way in which German industry employed men who knew how to apply science and engineering to design and production. The magnetic mine provides a good example of the excellence of German design. The only reason for the mine’s failure to cripple British shipping was that Germany went to war with only 1,500 of them in stock. After the first sequence of minelaying operations, the Germans had to wait until March 1940 for more to be manufactured.6 It was this respite that saved Britain’s defences from being overwhelmed, and provided an interval during which the menace could be countered.
Admiral Dönitz at his command post
From its creation, the German U-boat arm had its most important bases at Kiel and Wilhelmshaven, in that flat and lonely part of Germany that has long belonged to the German navy. To get to the Atlantic shipping, U-boats had to negotiate the narrow sea lane between Scotland and Norway. Worse, German coastal regions were shallow and could be mined. So, as soon as France was defeated, Admiral Dönitz moved his submarine fleet to its west coast which faced directly to the Atlantic. It was done with remarkable speed and efficiency. On his own initiative, Captain Godt, chief of staff to Dönitz, dispatched workmen from the Germania construction yards at Kiel, and selected men from the flotilla commands. A train loaded with fuel, torpedoes, supplies and paperwork departed from Wilhelmshaven on the day following the French armistice. Less than three weeks later, the U-30, commanded by Kapitänleutnant Lemp, was in Lorient, loading torpedoes. One account records that:
The advance guard of the flotilla staff had moved into the French Naval Prefecture at Lorient. They had plenty of booty – uniforms, footwear, equipment – some of it bearing the names of British and American firms and the date 1918: there were piles of tropical kits, arms, ammunition, food, and a thousand and one items which the enemy had had no time to destroy … And now the flotilla depot was there, with everything one’s heart could desire – transport, fuel, money; only the sanitary arrangements left something to be desired, but that was soon rectified.7
After a brief spell in Boulevard Suchet, Paris, Dönitz set up his headquarters in Kernéval, near Lorient, on 1 September 1940. His commandeered villa near the sea at Lamorplage had belonged to a sardine merchant. Sheltered by trees, it had a view towards Port Louis and the old fort at the harbour entrance. From here Dönitz could watch his U-boats as they came into the harbour and tied up at the wooden prison ship Isère which had once been used to transport French convicts to Devil’s Island in French Guiana. Now it was the first and last mooring for each U-boat that went on an operational trip. Comrades, female naval telegraphers and other well-wishers would gather on the Isère; sometimes a military band played patriotic songs and marches. U-boats departing had their crews paraded on deck; those arriving would often be flying the home-made pennants that denoted the tonnage of their victims.8
One room in the Dönitz mansion was called ‘the museum’. Here, by means of charts, diagrams and the graphs he liked so much, he could see, or show others, the progress of the submarine war measured by such things as the Allied tonnage sunk per operational U-boat day at sea. Here were the turn-round times and the changing enemy tactics and routes. The next room – his ‘situation room’ – had a big plotting table and walls covered with maps and charts. Pins showed the positions of the U-boats and of convoys and RN units, and even – thanks to the men of B-Dienst – the places where the British believed the U-boats to be! There were air-reconnaissance photos and, from secret agents, reports of the sailing of individual ships or convoys. On the map’s could be seen the way in which long-range Sunderland aircraft were being sighted further and further west. Dönitz described the room in which he spent so many hours:
The maps were supplemented by a number of diagrams showing the differences between our local time and that in the various areas of operations, charts showing tides and currents and ice and fog conditions with special reference to the northwest Atlantic … A large globe more than three feet in diameter gave a realistic picture of the wide Atlantic as it really is and was of great assistance in determining distances which could be worked out only approximately on ordinary charts, which, where great distances are concerned, make no allowance for the curvature of the earth’s surface.9
On that first day of September 1940 his charts showed that his U-boat losses to date – 28 – exactly equalled the number of new boats commissioned in the same period. That still left him fewer than at the start of the war because of the needs of training, repairs, trials and shakedowns. Of his 27 operational U-boats only seven or eight would be at sea on an average day, too few for Dönitz to operate the sort of ‘wolf-pack’ tactics he wanted, though sometimes several boats could be brought together to converge on a target.
The chart recording his successes would have shown an aircraft-carrier, a battleship, three destroyers, two submarines, five auxiliary cruisers and 440 merchant ships estimated at a total 2,330,000 tons. Dönitz used tonnage sunk per U-boat day at sea as a measure of the U-boat arm’s efficiency. By this measure October 1940 was the peak of his success, with five and a half ships sunk each month per U-boat at sea. (The high figures achieved later in the war were sinkings by larger numbers of boats, and Dönitz remained acutely aware of his failure to get back to his 1940 peak.)
The French bases at Lorient, Brest, St Nazaire and La Rochelle were near deep water and difficult for the British to mine. RAF Bomber Command did not mount an all-out bombing campaign against them until it was too late. For in 1941, at Hitler’s command, concrete shelters were constructed over the pens and made so thick and strong that normal RAF bombs had little effect. Virtually indestructible, these pens are still there today. The French show perverse pride in them and permit only their own citizens to look inside.
The Germans also had the benefit of skilled French technicians. Delighting their German masters, the French shipyard workers laboured even harder than their counterparts in Germany. They reduced the turn-around time that U-boats spent in port by no less than 22 per cent. ‘Until this time two and a half boats had been in port for every submarine at sea and the French helped to reduce this figure to a ratio of 1.8:1.’10
As German armies consolidated their conquest of France and the Low Countries in the summer of 1940, the British kept many destroyers and other craft in base, ready to repel an invasion of their islands. Convoys sailed with few escorts, and for much of the crossing had to manage without protection. Out in the North Atlantic the U-boats were sinking merchant ships at a dismaying rate. U-boat commanders, with their battered hats and white roll-neck sweaters, were coming home from patrol to report the sinking of forty or fifty thousand tons of shipping. These undersea aces got the same sort of film star treatment in Germany that the Spitfire pilots (often with similarly battered hats and similar white roll-neck sweaters) were enjoying in Britain. U-boat crews were cosseted. French resort hotels were converted to rest homes for them, or they could return to Germany on the special U-boat train that went backwards and forwards with supplies, ammunition and spare parts. If they stayed near their bases, their high pay (with double pay for each day in the Atlantic operational zone) ensured their warm welcome in restaurants, nightclubs and brothels despite their reputation for boisterous behaviour.
From the bases in France U-boat men could strike at ships bringing fuel, wheat and war supplies to Britain from the United States and Canada, as well as beef from South America, while the routes of vital ore from South Africa and oil from Nigeria were almost on their doorstep. The African convoys were seeking safety further west and the transatlantic routes were going ever more northwards into icy seas. The U-boats followed them.
Aircraft: the lonely sea and the sky
Until war started, the British had given little thought to the weapons needed if aircraft were to sink submarines. The Blackburn Kangaroo, a twin-engined biplane used against U-boats in the final weeks of the First World War, could carry four 250-lb bombs. The twin-engined Avro Anson, which in 1939 comprised well over half of RAF Coastal Command’s aircraft, could carry only four 100-lb bombs. Although these were specially designed anti-submarine bombs their efficiency had never been properly tested. The first chance to measure Coastal Command’s anti-submarine bombs came on 5 September 1939, two days into the war, when an Anson of 233 Squadron dropped two 100-lb bombs on a submarine that surfaced off the coast of Scotland. The bombs bounced off the water and exploded in mid-air, causing enough damage to bring the Anson down into St Andrews Bay. The submarine proved to be one of the Royal Navy’s fleet.
A few days later, on 14 September, two Blackburn Skua dive-bombers from the aircraft-carrier HMS Ark Royal attacked the U-30 which had surfaced alongside the freighter Fanad Head while a German boarding party searched for food (the U-boat rations had gone mouldy) prior to opening its sea valves to sink it. Again the anti-submarine bombs exploded in the air, bringing down both planes. The U-boat crew, commanded by Kapitänleutnant Lemp, rescued two of the aviators and then dived with them as prisoners. The next day another Anson was damaged by its own bombs without causing damage to the target. A year later, on 25 October 1940, three Hudson bombers from 233 Squadron subjected the U-46 to a concentrated attack in which one 100-lb anti-submarine bomb scored a direct hit. The U-boat’s pressure hull remained intact and the vessel managed to get back to port.
It is no surprise to learn that the first U-boat sinking from the air was carried out by Bomber Command using ordinary 250-lb general purpose bombs. A Bristol Blenheim on an armed reconnaissance went dangerously low to deliver a determined attack upon U-31, which on that day, 11 March 1940, was undergoing sea trials off Heligoland Bight. One, perhaps two bombs, hit the hull. Everyone aboard, including many dockyard workers, died though the hull was salvaged, refitted and went back into action. At last, a month later, a Fairey Swordfish flying off HMS Warspite did manage to score with two 100-lb anti-submarine bombs, sinking the U-64 at anchor.
In view of the ineffectiveness of the anti-submarine bombs, the airmen decided to throw at the enemy the only other anti-submarine weapon available: the depth charge designed in the First World War. This thin metal drum, packed with explosive, had an adjustable fuse which detonated according to water pressure. A nose and tail were fitted and it was dropped with reasonable success on practice targets, although only large aircraft could carry the depth charge since it weighed 450 lb. Altogether different to the bomb, it was designed to go into the water alongside the target rather than strike it (those that hit a submarine seldom exploded), and since the explosion took place underwater it posed far less danger to the airmen. But such depth charges were not in general supply until the summer of 1941.
In 1939 both sides were acutely short of large long-range aircraft. The Luftwaffe had been forced to use a civil airliner, the Fw 200C Condor, a beautiful machine that in August 1938 had flown non-stop from Berlin to New York and back at an average speed of 205 mph. Pressed into use for long-range maritime reconnaissance, the Condor was not rugged enough for the rigours of military flying.
The RAF had the equally fine Short Sunderland flying boat, a four-engined machine with a crew of anything up to 13. It came complete with kitchen and beds. Although it looked like the same manufacturer’s civil flying boat, this aircraft was built to a military specification and so was much better suited to a military role than the adapted Condor. One Sunderland, forced down on to a very rough Atlantic, with winds gusting up to 100 mph, remained afloat for the nine hours that it took HMAS Australia to arrive and rescue its crew.
The Sunderland had won headlines a few days after war began when two of them landed on the sea and rescued the 34-man crew of a torpedoed tramp steamer. Any flying boat – let alone one with a crowd of unscheduled passengers – is difficult to unstick from open water. It was a remarkable feat of airmanship, and seamanship too. With a range of almost 3,000 miles at 134 mph the Sunderlands would no doubt have seriously depleted the U-boat flotillas if suitable bombs or depth charges had been available in the early days of the Atlantic battle.
Since 1936 the United States navy had been using as their patrol plane a reliable two-engined flying boat which the RAF called a ‘Catalina’ after an island near Consolidated’s San Diego plant. The RAF ordered 30 of these aircraft in 1939 and they began arriving in 1941. It was one of these flying boats that sighted the Bismarck on 26 May 1941. The pilot who shadowed the German battleship was actually on a check flight with a US navy instructor aboard.11 They were flying out of Lough Erne in Northern Ireland, which in great secrecy had already been allotted funds and materials for conversion to a US naval air base. The official account of the interception seems to have had some expletives deleted:
I was in the second pilot’s seat when the occupant of the seat beside me, an American, said ‘What the devil’s that?’ I stared ahead and saw a dull black shape through the mist which curled above a very rough sea. ‘Looks like a battleship,’ he said. I said: ‘Better get closer. Go round its stem.’ … two black puffs appeared outside the starboard wing tip. In a moment we were surrounded with black puffs. Stuff began to rattle against the hull. Some of it went through and a lot more made dents in it … The only casualties occurred in the galley, where one of the crew who was washing up the breakfast things dropped two china RAF plates and broke them.12
During the Bismarck surveillance a Catalina created a Coastal Command record of 27 hours of continuous reconnaissance. The Cat was remembered by those who flew it for its particularly good auto-pilot, which made it possible to endure long hours at the controls of this heavy machine – patrols regularly lasted 17 hours – and meant there could be an extra pair of eyes watching for U-boats. Later, at the direct instruction of President Roosevelt, these flying boats were joined by another Consolidated aircraft: the B-24J Liberator, a four-engined aircraft with extra fuel tanks fitted. Able to carry antenna, radar sets, bombs, depth charges and even searchlights, the Liberator played a vital part in narrowing that mid-Atlantic ‘gap’.
Long-range flying was pioneered during the war by hastily trained young men plucked from civilian jobs. RAF Sunderlands flew a thousand miles out over the Atlantic, and did it day after day. When America entered the war Boeing B-17 Flying Fortress pilots, at the end of their US army air force training, flew their Forts to Britain. It was a Catalina delivered to Australia that made the third air crossing of the Pacific. In normal times these events would have made newspaper headlines.
Maritime patrol aircraft needed a very long range, for they had to reach the convoys far out in the ocean before work could start. Once in place, their chief value arose from the fact that U-boats had to remain below when aircraft were present, or risk being bombed. Even a slow 7-knot convoy would soon outdistance a submerged submarine, and a submerged submarine could be detected on asdic.
The start of a convoy’s trouble came when one of a rake of submarines spotted smoke, began trailing it at a distance, and then transmitted signals to bring others. A U-boat forced to submerge might well lose contact with the convoy and would have to cease transmitting.13
An unforeseen dimension of the encounter between aircraft and submarine was the fact that land-based aircraft could not pick up survivors in the sea. This brought an unexpected outcome in August 1941 when a Lockheed Hudson bombed U-570 in the open sea to the south of Iceland. The U-boat was one of the large long-range Type IXC vessels that were notorious for the way in which seawater came over the conning tower at above-average speeds or in rough weather. The bombs damaged U-570 enough for seawater to get to the batteries and create deadly chlorine gas: a constant worry for all submarine crews. The U-boat crew signalled surrender with the captain’s white shirt and then found a white board and waved that too. The Hudson circled with guns trained, not realizing that the U-boat could not dive again. While circling the pilot suggested that his co-pilot parachute down as a prize crew, ‘but he didn’t fancy it’ he joked in a BBC broadcast. A Catalina arrived and the Hudson signalled: ‘Look after our sub, it has shown the white flag.’ Ships sent to rescue the submariners arrived just before nightfall and took the U-boat in tow until eventually it ran aground off Iceland. It was refitted and put into action by the Royal Navy as HMS Graph.
Boffins join the navy
During the 1930s scientists in Germany, France, the USA and Britain, working independently and in secret, discovered that a beam of very short pulses, sent and reflected from a target back to a cathode ray tube, would define that object’s bearing and range. It was not advanced technology, and it certainly wasn’t a British invention. Even the Russian armed forces were equipped with radar by the time war began.
The German battleship Graf Spee had excellent gun-laying radar and the Scharnhorst and Gneisenau both used radar to evade HMS Naiad in January 1941. Naiad’s Type 279 radar was outranged by the German radar, so that after one brief visual sighting by the British (who never made radar contact) the German ships were able to keep clear of their pursuers. In the Norwegian campaign the same two German ships had surprised HMS Renown by using gun-laying radar to hit her while remaining concealed in a snow squall.
The Royal Navy began to equip its ships with Type 79 radar in 1939, although at the outbreak of war only HMS Rodney and HMS Sheffield had been fitted with it. These sets were intended for the location of enemy aircraft, and were given to the big ships and to anti-aircraft cruisers such as HMS Curlew, HMS Carlisle and HMS Caracoa. In May 1940 two hundred Type 284 (50-centimetre) gunlaying radar sets were ordered. New urgency was given to radar development when, in the Mediterranean in 1941, ships without it were found to be at a grave tactical disadvantage. The US navy had been fitting radar to its ships since 1940, and in the August of that year, long before the United States went to war, the USN and RN began to share their technology.
At the start of hostilities, German radar was more accurate and sophisticated than that of any other nation. The first radar success of the war was on 18 December 1939 when a formation of 22 RAF Vickers Wellington bombers was detected 70 miles off the German coast. Only ten of the bombers returned.
While British designers concentrated on longer-range sets, the Germans wanted accuracy and, where possible, mobility. In the summer of 1940 a German mobile unit on the Cherbourg peninsula fixed the position of an RN destroyer near the British coast and it was sunk by a Luftwaffe attack.
Radar – or Radio Direction Finding as the British called it at that time – was cumbersome, and the use of delicate glass vacuum tubes, known as valves, made it fragile. Such apparatus was regarded as a land-based, or shipborne, anti-aircraft weapon that could also be used against ships. It was probably the British who first tried another idea. A team under Dr Edward Bowen put an early EMI television receiver into an old Handley Page Heyford bomber and was encouraged by getting a flickered reception from a transmitter. From this they went on to design a small high-frequency set to go inside an Avro Anson aircraft. By 3 September 1937 it could detect big ships at about five miles.
The vital factor in the development of British radar was a willingness to improvise. Priority was given to radar – and other scientific ideas – when radar was credited with having saved Britain from defeat in the Battle of Britain. The Nazi creed gave emphasis to rural traditions and old ‘Germanic’ customs; and the political leaders of the Third Reich were apt to be antagonistic to modern science, sometimes defining it as Jewish. German scientists were not automatically exempted from military service, and civilian scientists assigned to work with the armed forces did not find the welcome that their British counterparts were given. Britain invented the technique of ‘operational research’, which meant scientists (cheerfully nicknamed ‘boffins’)14 advising the armed forces on the most effective way to use existing weapons rather than having to devise new ones.
Operational research boffins demonstrated that you could double the size of a convoy without doubling the length of its perimeter; in fact the perimeter of an 80-ship convoy was only one seventh longer than a convoy of 40 ships. Thus big convoys meant more effective use of escort vessels. Moreover average losses decreased from 2.6 per cent to 1.7 per cent when convoys comprised more than 45 ships. This was partly due to the fact that a wolf pack’s activities were limited by the availability of torpedoes, reloading time, stress and fatigue, whatever the size of the convoy.
Operational research also helped decide at what depth a depth charge should be set to explode. The scientists suggested that, given enough time, a U-boat crash-diving usually turned away to escape. Such targets should be abandoned as a lost cause. Depth charges dropped from aircraft should be set to explode near the surface, ensuring the more certain kill of those U-boats attacked early enough. Such ideas brought an immediate and dramatic benefit to British anti-submarine tactics.
When war began, Coastal Command had 12 Lockheed Hudson aircraft fitted with ASV (Air to Surface Vessel) Mark I radar. Better sets – fitted in the larger Armstrong Whitley bombers and Sunderland flying boats – followed. At its best, airborne radar could pick up a U-boat at 25 miles, but these valuable aircraft, with their ineffective anti-submarine bombs, seldom sank U-boats.
The boffins were asked why out of 77 U-boat sightings from aircraft in August and September 1941 only 13 were originated from airborne radar contact. The hastily built equipment was poorly serviced, they said, and operating it was a job assigned to anyone with time to spare. Better training gave aircrews faith in their equipment, and towards the end of 1941 airborne radar became more and more effective. Swordfish biplanes of 812 Squadron Fleet Air Arm showed what it could do by patrolling systematically by day and night against U-boats trying to get through the narrow Strait of Gibraltar in to the Mediterranean. One U-boat was sunk and five damaged so badly that they had to return to base.15
In addition, the Royal Navy’s big ships were being fitted with its own more sophisticated gun-laying as well as air-warning radar, yet the range of British radar sets was still less than that of an alert lookout on a clear day. The urgent problem was to develop something that could be fitted into an escort vessel, such as a corvette, and detect the conning tower of a surfaced U-boat at night.
Dr S. E. A. Landale was one of the team that set up a short-wave centimetric radar on the cliffs at Swanage and traced a submarine seven miles away. He found practical difficulties when fitting his radar into a ship: ‘Corvettes are very wet and in rough weather the discomforts, inconvenience and inflow of water whenever the office door was opened had to be experienced to be believed.’16 Antenna systems had to be protected against the weather. More problems arose from the rolling and pitching and the effects of engine vibration and of gunfire. Even so, by the end of 1941 the Type 271 radar had been designed, one hundred were built and fifty ships were equipped with it. This was the first operational magnetron-powered centimetric radar in the world. In use it was a revelation: it could even locate the top of a periscope. No longer could a surfaced U-boat sail at night with impunity.
Fragile but lethal: U-boats at work
But in September 1940, long before such sophisticated devices played a part in the battle, Admiral Dönitz became agitated enough to tell his staff that ‘It will not be long before the entire U-boat fleet is lost on our own doorstep.’ His distress was due to two factors which still today have scarcely been recognized, says one of the most reliable historians of the U-boat war, J. P. M. Showell. Dönitz was distressed about the number of boats lost to British submarines and mines while crossing the Bay of Biscay. The dangers of the Bay had led U-boat crews to call it Totenallee, or death row.
Leaving aside the efficacy of the mines and submarines, the fears that Dönitz showed were to have an immediate and immense effect upon the U-boat war, for he told his crews to send a radio signal as soon as they had traversed the Bay safely. This signal was transmitted when the U-boat passed the 10 degrees west line (later this was changed to 15 degrees west). The crews looked forward to this stage of the journey, for their daily rate of pay increased. The Admiralty’s Submarine Tracking Room personnel also liked it for, using HF/DF, an exact longitude could now be added to an approximate latitude for every U-boat going on patrol. With this ‘fix’ pinned in to the map it was usually possible to guess which of the convoy routes the U-boat was heading for.
Operating with less than 30 U-boats, Dönitz was fretting for a chance to experiment with his ‘wolf pack’ tactics. His theories about surface engagements were confirmed. Nearly three-quarters of all successful torpedo attacks were made at night from surfaced U-boats which could not be detected by asdic apparatus. At this stage of the war there were vast areas of ocean where Allied aircraft were never seen, allowing U-boats to function more like torpedo boats than submarines.
Even without the men of B-Dienst the U-boat men could roughly estimate a probable convoy route. Dönitz would assign some his available U-boats to line up across it and wait on the surface, watching for a smudge of smoke on the horizon. When a convoy was sighted, the other U-boats would be called in. Some would be too far away, others would fail to find the rendezvous, but a force would assemble. After dark, without submerging, the U-boats sailed right through the columns of ships. Even on a dark night the sky is faintly visible, and from a conning tower it was usually possible to see the outlines of ships high above. On the other hand U-boats were small, and even in daylight the low silhouette of a conning tower was not easy to spot in the grey Atlantic water.
In October 1940 the experts at B-Dienst provided a map reference for the 35-ship convoy SC 7, a slow convoy out of Sydney, Nova Scotia, made up of five columns of four ships and, in the centre, three columns of five ships.17 The columns were half a mile apart, each ship 600 yards from the one ahead. This typical broad-fronted rectangle was less likely to straggle and, since U-boats preferred to attack from the flank, it provided a smaller target than a long rectangle.
Thus convoy SC 7 covered an area of about five square miles and was protected by two sloops and a corvette. A gale came and the convoy straggled. Four Great Lakes steamers, not intended for Atlantic rollers, fell back and were lost (U-boats sank three of them). In looking for U-boats, one sloop lost contact and never found the convoy again. U-boats converged. Here was Günther Pried, who had crept into Scapa Flow to sink Royal Oak. Here was Joachim Schepke, adding up his score of sunken tonnage. Here was ‘Silent Otto’ Kretschmer, promptly sinking four ships and finishing the last one off with his 8.8-cm deck gun. The sinkings went on and on until 17 ships were lost and the convoy’s passing was marked by survivors in open boats and drowned men floating amid the oil and wreckage. It was October, and in the northerly latitudes the convoys were forced to take the wind was bitterly cold, the seas heavy and the days short. Thirty minutes immersed in the North Atlantic was enough to kill most men. Survivors in an open boat had little chance of reaching land, or of sighting another ship.
The assembled U-boats, feasted and happy, were just in time to encounter the HX 79 (a fast convoy out of Halifax). That night 14 more ships went down. But the slaughter was not finished, for the U-boats found yet another convoy, HX 79A, and on that same night sank seven of them.
Before October was ended, there came another blow to Britain’s maritime fortunes. A Focke Wulf Fw 200C Condor, far out over the ocean on a long route from Bordeaux to a base in Stavanger in Norway, spotted the Canadian-Pacific liner Empress of Britain about 70 miles from Donegal Bay in the north of Ireland. She was carrying servicemen and their families home to Liverpool. Captain Bernhard Jope of I/KG 40 group was at the controls of his four-engined plane and this was his first sortie. Bombs dropped from very low level set the liner afire and it was finished off by a U-boat’s torpedoes. Jope received the Knight’s Cross. After the war he became a Lufthansa captain.
The loss of the Empress of Britain was not an isolated incident. Aircraft played an important part in the battles of the sea lanes, and by war’s end no less than 13 per cent of Allied shipping losses were attributed to air attack. (The U-boat arm accounted for 69 per cent of shipping losses; surface raiders and mines for 7 per cent; navigational hazards and reasons unknown for 4 per cent.)
The bombing of the convoys prompted Churchill to increase the air patrols around northern Ireland but they remained inadequate. A more desperate measure was to shoot a Hawker Hurricane fighter plane from a small platform fitted to a tanker’s deck. After, combat the pilot was instructed to ditch his plane into the sea near the convoy and be rescued. It was a grim prospect. The first catapult-equipped ship sailed for New York in May 1941 but was the victim of a U-boat. The first kill by such a ‘Hurricat’ was not until August. Few German planes fell victim to the new device. The MSFU (Merchant Ship Fighter Unit) was a deterrent rather than a weapon, and as the word spread that convoys could produce this spiteful jack-in-the-box, the long-range Condors grew more wary.
Of course not every convoy was attacked from the air or by U-boat. A German historian thinks about nine out of every ten convoys escaped. But there were not many sailors who spent six months at sea without seeing flashes and flames in the night, and a dawn that exposed spaces in their ranks. Only a few sailors took off their shoes – let alone any other articles of clothing – when they went to sleep.
The battle at its peak
After a slow start in 1941 the U-boat building programme began to bear fruit. By the end of the year Dönitz had 247 boats to command. His losses were going up slowly: 9 in 1939; 26 in 1940; 38 in 1941. His building rate was 64, 54, 202.
In the opening months of 1941 the long-range German reconnaissance aircraft showed their teeth. In January aircraft sank 20 ships, while U-boats sank 21. In February the U-boats sank 39 ships while aircraft added 27 and surface raiders brought the total to over one hundred (and over 400,000 tons for the first time since October 1940). More than half the ships lost during this period were stragglers, alone and defenceless.
Dönitz calculated that sinkings (including those by the Luftwaffe) must reach 750,000 tons before Britain could be forced to surrender. The British set the red-line at 600,000 tons. On the charts at his headquarters at Kernéval, the rate of Allied sinkings for early 1941 was shown as 400,000 tons per month. In fact his captains – awarded medals on the basis of tonnage sunk – were giving him outrageous estimates of the size of their victims.18 But the losses were grave nevertheless, especially when augmented by the depredations of aircraft and surface raiders (see Table 1).
Table 1
Allied shipping losses May–Nov. 1941 (total gross register tonnage)
| Claimed | Actually sunk | |
| May | 421,440 | 367,498 |
| June | 441,173 | 328,219 |
| July | 227,699 | 105,320 |
| August | 168,734 | 83,427 |
| September | 399,775 | 207,638 |
| October | 601,569 | 370,345 |
| November | 85,811 | 68,549 |
In the early part of 1941 RAF Coastal Command was put under the operational control of the navy, and a reconnaissance squadron was sent to be based in Iceland. British air activity, as little as it was, persuaded Dönitz that he too must have air cover for his submarines. He had the experienced bomber group I/ KG 40 put at his disposal. After January 1941 Condor aircraft regularly ranged far out into the Atlantic between Bordeaux and Stavanger in Norway. As time went on, Allied ships had enough anti-aircraft weapons to deter bombing attacks. It then became the task of these four-engined planes to scout specific convoy routes, provide Atlantic weather reports and cooperate with the U-boats.
In fact there were too few Condors to make much difference, and despite using radio beacons, few Luftwaffe navigators could pinpoint a position exactly enough to bring a U-boat within sighting distance of a convoy. To add to the confusion, the Luftwaffe map grids did not tally with the navy’s charts. At this time, anyone standing at the bar in a U-boat mess could get an easy laugh from any joke about ‘air support’. The unseen value of aircraft in the Atlantic battle was the morale boost they gave to their own side and the disturbing sight they made for any enemy seaman.
At first the convoys outward-bound from Britain had been given RN escorts on only the first stage of their journey, about 15 degrees west longitude. Then the escorts stayed as far as 25 degrees west and then – by July 1941 – convoys were given continuous escort. Relays of escorts operated from Britain, from Iceland and from Newfoundland. But warships were scarce, so that even by the end of 1941 the average convoy had no more than two escort ships.
The escort ships were not immune to torpedoes either. I make no apologies for the extra length of this excerpt from one of the most graphic accounts the Atlantic battle provided:
The sky suddenly turned to flame and the ship gave a violent shudder … Looking ahead, I could see something floating and turning over in the water like a giant metallic whale. As I looked it rolled over further still and I could make out our pennant numbers painted on it. I was dumbfounded. It seemed beyond reason. I ran to the after-side of the bridge and looked over. The ship ended just aft of the engine room – everything abaft that had gone. What I had seen ahead of us had really been the ship’s own stem. There were small fires all over the upper deck. The First Lieutenant was down there organizing the fire parties. He saw me and called, ‘Will you abandon ship, sir?’ ‘Not bloody likely, Number One … We’ll not get out till we have to.’
But a ship with its stern blown away does not stay afloat for long:
The deck began to take on an angle – suddenly – so suddenly. She was almost on her side. I was slithering, grasping all kinds of unlikely things. My world had turned through ninety degrees … I jumped for the galley funnel which was now parallel with the water and about two feet clear, and flat-footed it to the end. I paused at the end of my small funnel to look at the faces. They were laughing as if this were part of some gigantic fun fair. The men called to me.
‘Come on, sir. The water’s lovely.’
‘I’m waiting for the Skylark,’ I shouted back. But the galley funnel dipped and I was swimming too – madly … We swam like hell. I turned once more, but now there were very, very few bobbing heads behind me. I swam on. The destroyer of my old group was passing through us. I could see her men at action stations. They were attacking. They were attacking the wreck of the Warwick! I screamed at them in my frenzy. Wherever else the U-boat might have been it could not have been there. The depth charges sailed up in the air. Funny how they wobbled from side to side, I’d never noticed that before. When, I wondered, would they explode? It was like being punched in the chest, not as bad as I had expected. I swam on. Things were a bit hazy. I was not as interested in going places as I had been. I could only see waves and more waves, and I wished they would stop coming. I did not really care any more. Then I felt hands grasp my shoulders and a voice say, ‘Christ, it’s the skipper. Give me a hand to get the bastard in,’ and I was dragged into a Carley-float which was more than crowded to capacity.19
To make the most of their pitifully few escorts, the RN had started ‘Escort Groups’, which usually meant in effect nothing more than RN captains getting together – under one of their number named as escort group commander – to exchange ideas about anti-submarine tactics.
It was the 5th Escort Group which in March 1941 was in the same area as the German navy’s three most famous U-boat captains: Günther Prien, Joachim Schepke, the celebrated and colourful captain of U-100, and Otto Kretschmer of U-99. At their collars these men wore the Ritterkreuz, to which the insignia of the oak leaves had been added to celebrate 200,000 tons of ships sunk. Kretschmer and Schepke were both determined to be the first to sink 300,000 tons of Allied shipping. Kretschmer had left his base at Lorient credited with 282,000 tons (although, as we have seen, such German figures were usually very much inflated).
It was Prien in U-47 who sighted the outward-bound convoy OB 293 and summoned his colleagues: Kretschmer, Matz in U-70 and Hans Eckermann in UA.20 Although a primitive seaborne radar set played its part, this encounter marked little change in the methods or technology of either side. But there was a change in the men: the Germans, solidly professional, were at the zenith of over-confidence, while the Royal Navy’s landlubbers and weekend yachtsmen had discovered a new determination.
Kretschmer started the sinkings. Firing while surfaced, he hit a tanker which burst into flame and a Norwegian whaling ship Terje Viken which remained afloat. Using the same tactics in U-70, Matz hit a British freighter and the Mijdrecht a tanker, which with true Dutch resilience steered at him and rammed as U-70 dived. The UA was detected and dived, its course followed by asdic. Depth charges damaged it enough to make the German set course for home.
Matz in U-70 had submerged. He now came under coordinated attacks from two corvettes. Wallowing and unstable he went to 650 feet: far deeper than the submarine was designed to endure. The damage sustained from the Dutchman which rammed him, together with the depth-charging, started leaks and made the U-boat impossible to control. Despite the crew’s efforts the U-70 surfaced and was fired upon. The crew surrendered as the stricken boat reared, bow in the air, and slid under, taking 20 of the crew with it.
Even the stubborn Kretschmer dived deep and sat ‘in the cellar’. He watched the rivets pop and the lights flicker as the explosions came and went. Carefully he withdrew, with half his torpedoes still unused. The convoy sailed on, having lost two ships, and had two damaged.
Prien followed the convoy and tried again at dusk, his approach covered in fitful rainstorms. But in a clear patch he was spotted by a lookout on HMS Wolverine and his crash-dive failed to save him from the depth charges that damaged his propeller shafts. Instead of turning for home, he surfaced after dark for another attack, perhaps not realizing how clearly the damaged propellers could be heard on the asdic. This time Wolverine, which had tenaciously waited in the vicinity, made no mistake. As the U-boat crash-dived, an accurately placed depth charge caused the submarine to explode under water, making a strange and awful orange glow. ‘The hero of Scapa Flow has made his last patrol,’ said the obituary notice personally dictated by Admiral Dönitz when, after 76 days had passed, they finally told the German public of their hero’s death. Even then stories about him having survived circulated for months afterwards.
A few days later on 15 March 1941, south of Iceland, Fritz-Julius Lemp, now promoted to Korvettenkapitän, signalled the approach of a convoy. It was an attractive target but the escort was formidable. The escort commander was Captain Macintyre RN, who was to become the war’s most successful U-boat hunter. He was in an old First World War destroyer, HMS Walker. There were four other old destroyers with him, and two corvettes. The homeward convoy HX 112 consisted of almost 50 ships, in ten columns half a mile apart. They were heavily laden tankers and freighters, and even in this unusually calm sea they could make no more than 10 knots (11.5 mph).
Lemp’s sighting signal was intercepted by direction-finding stations in Britain. Such plots could only be approximate, but Captain Macintyre was warned that U-boats were probably converging on HX 112. Without waiting for other U-boats, Lemp’s U-110 surfaced and used darkness to infiltrate the convoy. Two torpedoes from his bow tubes missed, but one from his stern hit Erodona, a tanker carrying petrol, and the sea around it became a lake of flames.
The next day other U-boats arrived. The uncertainties of U-boat operations are illustrated by the way in which U-74 never found the rendezvous and U-37, having surfaced in fog, was run down by a tanker and had to return to base for repairs. But Schepke (U-100) and Kretschmer (U-99) provided enough trouble for the resourceful Captain Macintyre. Having spotted Schepke’s boat, the escorts started a systematic search which kept it submerged and allowed the convoy to steam away. At this stage of the war the escorts had not discovered that U-boats impudently infiltrated the convoys to fire at point-blank range. The search for the attackers always took place outside the convoy area. So the chase after Schepke was Kretschmer’s opportunity to penetrate the columns of the virtually unprotected convoy, and at 2200 hours there was a loud boom which marked the beginning of an hour during which Kretschmer hit six ships. Five of them sank. The hunt for Schepke’s U-100 was abandoned as the escorts closed upon their charges.
Schepke’s U-100, damaged by the continuous attacks, soon caught up with the convoy. Although a surfaced submarine was immune to asdic, it was vulnerable to detection by radar, and despite the darkness he’d been detected a mile away by a primitive Type 271 radar set aboard the escort HMS Vanoc. A surfaced submarine, if spotted, did not have much time in which to dive to safety. This was Schepke’s predicament as Vanoc was suddenly seen accelerating to full speed. As she sped past HMS Walker, the escort commander ordered a signal made to caution her about speeding. He received the reply ‘have rammed and sunk U-boat’. By that time the shriek of the destroyer’s bow tearing through the steel U-boat came echoing through the night air. Schepke and the duty watch standing on the tower were all crushed and lost. Someone below gave the order to crash-dive but depth charges ripped the hull open and U-100 sank with all but seven of its crew.
While Vanoc was repairing its damage, and picking up German survivors, HMS Walker’s asdic showed another U-boat nearby, and then the set broke down. This brief encounter was with Kretschmer’s U-99. It was surfaced and heading home under cover of darkness. Kretschmer was below. On the conning tower there was the usual complement of four men: an officer, a petty officer and two ratings. Each man was assigned a quarter of the horizon to watch through his Zeiss 7×50 binoculars. Lighter, smaller and more waterproof than RN binoculars, such glasses were coveted by every Allied sailor who saw them. The officer occasionally swept the entire horizon: it was the routine. Suddenly they came upon the warships that had sunk Schepke’s boat. One of them was searching for survivors. One of the German lookouts on U-99 saw the moonlight reflecting off a gun turret: it was a destroyer about 100 yards away. Had they done nothing they would probably have escaped – standing orders said submarines sighting the enemy at night must stay surfaced – but the submariners were tired. Thinking he’d been seen, and contrary to orders, the officer on watch dived the U-99, and it was then that Walker’s asdic operator saw it briefly before his screen went blank.
The Walker’s depth charge attack had to rely upon skill, instinct and practice. Those first explosions brought Kretschmer’s damaged boat to the surface. Both destroyers opened fire. ‘With an understandable enthusiasm,’ rescued merchant seamen taken on board the Walker piled up so much ammunition around the guns as to cause confusion.
Kretschmer was forced back to the surface. All torpedoes expended and his boat crippled, he realized that his career was at an end, but his tonnage claims were foremost in his mind. He ordered his radio operator to send a message claiming 50,000 tons of shipping and telling Dönitz that he was a prisoner of war. When Kretschmer saw Walker lowering a boat he took it to be an attempt to capture his submarine. He sent his engineer officer to flood the aft ballast tanks so that the U-boat would sink stern-first. It reared up suddenly and steeply, and slid back into the ocean, leaving the crew swimming. When he climbed aboard the ship that rescued him Kretschmer still had his binoculars round his neck and wore the white-topped hat that had become a captain’s prerogative in the U-boat service. All but three of the U-boat’s crew were saved, but the engineer officer was one of those lost. Captain Macintyre, the escort commander, used Kretschmer’s Zeiss binoculars for the rest of the war.
Kretschmer, a prisoner aboard HMS Walker, remarked to George Osborne, her chief engineer, upon the coincidence that both ship and submarine had a horseshoe badge but one was the wrong way up. It was explained to him that in Britain a horseshoe pointing down is considered bad luck. An eyewitness said ‘it brought a rueful laugh from our prisoner.’
A destroyer was a cramped place, even without shipwrecked seamen and enemy prisoners aboard, and there was evidence of bad feeling. But the master and chief officer of J. B. White, a sunken merchant ship, and Otto Kretschmer an unrepentant Nazi, were persuaded by the chief engineer to join him in a game of contract bridge. Osborne said it was the only decent game he managed to get in the entire war.
Germany had lost her three U-boat aces and the Propaganda Ministry discovered that stardom for fighting men is a two-edged weapon. The loss of three ‘experts’ made Dönitz suspect that the British must have some new secret weapon. But then he changed his mind and decided it was just bad luck.
Dönitz had been right with his first guess. HMS Vanoc had used a primitive radar set, and in this same month, March 1941, a far more sophisticated 10-centimetre set was being tested at sea. It was the cavity magnetron which made such advanced radar possible and put the British work far ahead of the Germans. But in the summer of 1941 the range at which radar gave the first indication of an enemy’s presence was not always better than an alert observer could provide on a clear day. In May 1941 the pursuit of the Bismarck provided a better example of the contribution radar played in the naval encounters of that period.