Chapter 5. The Second Happy Time: January–June 1942

The entry of the USA into the war following Pearl Harbor was seen by the U-boat staff as presenting both short-term advantages and long-term dangers. It was appreciated that it would take the USN some considerable time to introduce convoys for their east coast shipping, which would make fine targets for the increasing number of U-boats entering front-line service. On the other hand, they correctly estimated that the might of American industry would greatly increase the rate at which new merchant ships and escorts would be built and put into service.

In June 1942 the German estimate was that the Allied total merchant shipbuilding output for the year would be about seven million tons, a figure which proved to be almost exactly correct. To destroy the Allied shipping capability, it was estimated that U-boats must sink 800,000 tons each month (200,000 more than the corresponding figure in 1917). This figure was never going to be easy; in the last six months of 1941 the monthly rate was only about 125,000 tons, but in that period the number of boats on station was between fourteen and seventeen. In early 1942 it was expected that this number would increase rapidly. However, Hitler insisted on a strong force in the Mediterranean – about twenty in late 1941 – and another twenty to protect Norway. It is of interest that the Norway-based U-boats sank only twenty-five ships in the seven months to July, and of these, no less than sixteen came from the ill-fated PQ17 convoy.

The first wave was far fewer in numbers than Dönitz wanted: two Type IX and three Type X¹ boats deployed between Newfoundland and Cape Hatteras. At the same time, seven Type VIIC were sent to operate to the south of Newfoundland. The appalling cold weather and heavy groundswell over the Grand Banks caused many torpedo failures and they sank only two or three ships each. Two more Type VIIC followed in February and these ventured further south to Cape Hatteras. In doing so they demonstrated that the endurance of this class could be stretched by about three weeks as a result of the acceptance by the crew of great hardship. The deck of the passageway was covered with layers of tinned food and at least one toilet cubicle was packed with food.

There was no convoy system off the US coast until the middle of May; shipping followed prewar routes close to the shore. There was no blackout in coastal towns, so that, at night, ships were silhouetted against this bright background. Lighthouses, buoys and even ships’ own navigation lights were left burning as in peacetime. The few escorts, mainly World War I PC and ‘Eagle’ boats were deployed as ‘hunting groups’. There were also a few, very effective, Coast Guard cutters. The old fallacy was dragged out – that a weakly defended convoy was worse than no convoy – and once again proved wrong. Starting on 1 April, a limited escort system was operated. Ships would be escorted during daylight hours by auxiliary patrol vessels, armed yachts and the like, and spend the night in defended anchorages.

The RN lent ten corvettes and twenty-two A/S trawlers from their own escort force. An American building programme began to deliver both A/S vessels and also minesweepers that could be used in the A/S role. The USN had relearned the lessons of 1917–18, though at tragic cost. By mid-May a full convoy system was in operation and losses off the USA fell rapidly. Dönitz switched his attack to the Caribbean, made possible by the entry into service of the first two U-tankers, Type XIV milch cows (see the next section). They could carry enough fuel to extend the endurance of the Type VIIs by about four weeks. The four-rotor Enigma machines came into use in February 1942, and for the rest of that year the U-boat code could not be read at Bletchley Park. This silence added greatly to the safety of the Type XIV boats, which had to use radio to communicate with their customers. From mid-May until convoy was introduced in the Caribbean in mid-July, losses were again heavy but fell off with the use of convoys.

Phase 4 of the Atlantic battle: the U-boats’ second ‘Happy Time’. Sinkings were almost all in the Eastern Atlantic, mostly but not entirely very close to the coasts of the USA and Caribbean islands.

The number of U-boats at sea rose from forty-two in January to seventy in July, but that includes boats in transit as well as those in the Mediterranean and off Norway. There were rarely more than a dozen in the rich grounds off America. In January 1942 there were 110 RN and 67 RCN Flowers in the Atlantic, plus a few sloops and destroyers. The great majority of sinkings by surface ships was still attributed to destroyers (see table 5.1).

Painful as these losses in early 1942 had been, they were not decisive; worldwide, the monthly sinkings had averaged about 480,000 tons (with a worst month – June – of 637,000), far less than the target of 800,000 tons. The U-boat staff estimate of merchant shipbuilding also fell short of the reality in 1943. They estimated a total build of 10.8 million tons, whereas the actual output was 15.1 million tons. But the darkest hour is just before the dawn.

Technical Developments

Much development work was going on but, in most cases, the resulting equipments were only available in a later period.

Asdic

The Type 144 owed much to the earlier 128 but was completely redesigned. Type 144 used the retractable dome of Type 128, and the very similar 145 for slower ships used the detachable dome of the ‘trawler’ set Type 123. It is sometimes suggested that the 123/145 sets were inferior in capability, but this is not so; the slower ships did not need a retractable dome.

The design of the 144 began in about May 1941 and the first sets entered service a little over a year later. It was designed to control ahead-throwing weapons, first Hedgehog and then Squid, but could also direct a conventional depth charge attack. The electronics were redesigned to improve discrimination, picking out a target from background noise. Range and bearing recorders were also redesigned and drove repeaters on the bridge and in the wheelhouse. These provided data on the course to be steered and the point at which the weapon was to be fired. The slope of the trace gave closing speed. The transducer trained automatically in 5º steps (half that as it trained across the ends of a target), so that the operator only had to select port or starboard.

Codes

On 1 February 1942 the Germans introduced an additional rotor to their Enigma machines, multiplying the number of solutions twenty-six times. Enigma was unreadable for many months, though direction finding was becoming more useful with HF/DF sets on many ships. The pattern of signals also helped. On 30 October 1942, U-559 was blown to the surface by the destroyer Petard and the weather code book was recovered, though two sailors were drowned trying to get the Enigma machine. The code book was printed with water-soluble ink but much was readable. With this as a crib, the machine cipher was solved – with difficulty, but by December Bletchley Park was reading most signals (with some delay).

As built the Egret class had four twin 4in mounts, but in this 1943 photo the name-ship of the class has lost X twin 4in mount

The blackout in decoding Enigma coincided with the second ‘Happy Time’ for the U-boats, in early 1942 off the eastern coast of the USA. But it was not a direct cause, as the number of ships sunk fell dramatically when US coastal convoys were introduced. By early February 1943, signals were being read with little delay. On the other side of the hill, B-Dienst had broken Allied Cipher No. 3 and was decrypting some 80 per cent of signals, though there was considerable delay and probably only about 10 per cent were read in time to be of use.

Type XIV U-boats – Milch Cows

During the winter of 1939/40, U-boat Command considered means of increasing the time on station, in particular, reducing the time spent in transit. This led to idea of a ‘U-tanker’, carrying a large quantity of fuel, which could be transferred at sea to the attack boats. The Type XIV was the result; based on the Type IX but shorter, it carried 432 tons of fuel supply (figures differ), as well as 203 tons for its own use. Own fuel and cargo were interchangeable. The Type XIV had no armament other than light AA, giving more internal space. This meant that it could carry a considerable quantity of provisions (thirty tons), with a large cold room. It also carried spare parts and fifteen tons of lubricating oil, and could supply fresh water. There was a doctor, who could visit customer U-boats and carry out minor treatments. More-seriously ill or injured men could be brought on to the XIV and exchanged for one of her crew.

They completed in small numbers from the end of 1941, but it was well into 1942 before the first was operational. Before long, it became clear that the greatest benefit was not so much in reducing transit time but more in reducing the frequency of crossing the hazardous waters of the Bay of Biscay.

The refuelling operation was difficult and lengthy. First, the customer had to make contact with its tanker. This was usually done by specifying a square on the U-boat grid. However, each square was six miles across and submariners were reluctant to use lights and even more so to use radio homing. Once contact was made, a line had to be got across, usually using a rubber dinghy with the submarines stopped some 80–100 metres apart. The line would then be used to pull the hose across and fuelling could begin. The pumping rate was 30–35 tons per hour but not much more than half that rate was achieved, allowing for interruptions. While this was going, on the doctor could visit, lubrication oil would be supplied through a different hose and provisions would be transferred. The demand for provisions was usually slight, although fresh bread was welcome. Often, a second customer would be waiting. The exercise was dangerous and there was a steady toll of men lost overboard.

Arranging a meeting involved several signals between the boats and HQ. The introduction of the Type XIV coincided with a blackout on Enigma, making their frequent use of radio less dangerous. From early 1943, these signals were being read by Bletchley Park; most milch cows were sunk in mid-1943, only U-490 surviving into 1944.

Post-war analysis suggests that the concept of replenishment U-tankers was valid and cost-effective. However, this was true only if arrangements for a meeting could be made without the signals being either read or used for direction finding.

Later Sloops – Black Swan

The concept of the general-purpose sloop was gradually abandoned. In 1931 the minesweeping function was devolved to the Halcyon class of specialist sweepers. Fleetwood showed the potential of a heavy, mainly AA, armament (two twin 4in guns) and in 1933 this led to the ‘ocean convoy sloop’. The first of these was Bittern; however, she completed as the Admiralty Yacht Enchantress, and her sister Stork became a survey vessel. The third, finally taking the name Bittern, completed with the intended armament of three twin 4in AA guns. This was a very heavy armament when the latest cruisers had only four twin 4in AA. The mountings were unstabilised and to improve their accuracy it was decided to fit Bittern with the, then, novel Denny-Brown active fin roll stabilisers (discussed later). Four similar ships were built for the RIN.

Black Swan with pom-pom on the quarterdeck.

Sloop design was now in the hands of some outstanding constructors, led by Victor Shepheard (later Sir, DNC), with Ivor King (Director of Dockyards), followed by Rowland Baker (Sir, Dreadnought Project Team) as assistants. With Grimsby, the weight and stability problems of the early classes were finally overcome and the weighed weights of Enchantress were ‘fantastically accurate (for which I take all credit.)’.²

Fin stabilisers were a personal enthusiasm of the new DNC, Stanley Goodall, who was to tell the RAN that they were wasting their money if they built an unstabilised sloop.³ Control theory was in its infancy and it was easy for the fins to make things worse; there are delightful stories of Bittern rolling heavily in a calm sea. When they were set up by experts for a trial, the results were favourable but in less skilled hands they helped little and many thought that the space they occupied would be more use as fuel tanks.

Bittern was followed by three ships of the Egret class with four twin 4in AA, although with only one HA director control tower (DCT) they could only engage a single target.⁴ The first two ships of the Black Swan class were ordered under the 1937 programme and two more under the 1939 programme (with four for India). Initially, these two ships were fitted for wire minesweeping (Black Swan was fitted for minelaying). Another four were ordered under the 1940 programme, including Whimbrel, the last of these classes to survive, as the Egyptian Tariq. They were a little bigger than the Egrets, differing mainly in that the quarterdeck twin 4in gun was replaced by a four-barrel pom-pom. Some Black Swans were fitted with Hedgehog by October 1945.⁵

Later ships had the beam increased to 38ft 6in and other changes, becoming the Modified Black Swan class. Further ships were ordered: fourteen under the 1940 Supplementary Estimates, eleven under 1941 (two cancelled) and three in 1944 (39ft 6in beam – all cancelled). The original design had a close-range AA armament of a four-barrel pom-pom on the quarterdeck and quadruple 0.5in machine guns sited abaft the funnel. These were replaced by single Oerlikons, fitted on build in later ships. Single Oerlikons were fitted in the bridge wings in all ships as they became available, and replaced at the end of the war by single Bofors. When the first ships of the ‘Modified’ class completed, light AA guns were still scarce and they received what was available. At least three ships had four-barrel pom-poms sited amidships, while others had twin power-operated Oerlikons. Eventually, most had two twin Bofors amidships, two twin Oerlikons on the quarterdeck and single Oerlikons on the bridge wings.

An early shot of Cygnet with two 4 barrel pom-poms amidships.

Crane was a Black Swan class sloop, seen here in original configuration. Note the crowded quarterdeck.

Displacement (tons): 1,960 deep

Dimensions (feet): 283 oa x 37¾ x 11¼

Shp and speed (kts): 4,300 = 19.25

Fuel (tons), endurance miles @ (kts): 420, 6,100 @ 15 (trial)

Complement: 192 (original)

Early ships completed with a tripod mast, which soon carried a Type 268 radar. Later a 271 was added on a short lattice mast aft and by the end of the war most had a lattice foremast with Type 293. The gun director had Type 285. Early ships had a considerable amount of splinter protection but most of this was later removed to restore stability.

There were eight depth charge throwers with up to 110 charges. Some had a split Hedgehog on B gun deck.⁶ Asdic Type 144/147 was fitted. The effect of this increased armament can be seen in the electricity-generating capacity. Originally they had two 70kW steam-driven generators and one 50kW diesel-driven generator. This was increased to two 100kW steam and one 70kW diesel.

Their structure was to warship standards, although they were built of mild steel. Earlier ships were all riveted but the amount of welding gradually increased, with up to 30 per cent welded in some later ships. The design stresses in the original Black Swan were low: hogging/sagging figures were 5.7/5.0 tons/in² on deck and 3.7/4.3 tons/in² in the keel. Additional weights would have increased these stresses slightly but the deep hull to the long forecastle would have kept them on the low side. There are reports of splits in the forecastle deck, probably due to single-riveted seams. Cracks are also reported in the shell forward and in the area of the break of forecastle, well aft. There is no information on the cause but poor detail in these early examples of welding is probable. They were the Rolls-Royces of the escort force and their turbine machinery meant that they were built by experienced warship builders.

Wood decks were not fitted because of the shortage of timber, and other shortages led to a variety of unsatisfactory substitutes. The wood deck had also acted as thermal insulation to spaces below, so that as the increased complement made condensation even worse, lagging was fitted and ventilation improved.

Peacock is little changed in this 1951 photo by the author.

Starling was Captain Walker’s ship. She was directly concerned with sinking seven U-boats and present at the demise of several more.

Capt F J Walker and the 2nd Escort Group⁷

The Black Swan class should always be associated with the memory of the ‘ace’ U-boat killer Capt ‘Johnnie’ Walker. Walker’s naval career began as a cadet in the cruiser Cornwall in 1913 and he was a midshipman in Ajax when the First World War broke out. After promotion to sub-lieutenant in 1916 he spent the rest of the war in destroyers. As lieutenant, he served in Sarpedon and after the war in Valiant. In 1921 he began a series of courses that would make him one of the earliest ASW specialists in the RN. He was fleet A/S officer of the Atlantic Fleet in 1926–8, followed by a similar post in the Mediterranean until 1931, when he was made commander. He commanded the Shikari (control ship for the radio-controlled target Centurion) and then the Falmouth. From 1936–7 he was the commander of Valiant, after which he returned to A/S work as Experimental Commander at Portland. This could have been the end of his career, as he passed out of the zone for promotion to captain. When the war began, he was still at Portland but in January 1940 he joined the staff of Adm Ramsay at Dover, where he later played a part in planning the evacuation from Dunkirk.

In October 1941, Cdr Walker was appointed to command the 36th Escort Group from the sloop Stork. The rest of the group consisted of the older sloop Deptford and the corvettes Vetch, Rhododendron, Pentstemon, Gardenia, Convolvulus, Samphire and Marigold, though other vessels would reinforce the group from time to time. His group was mainly employed on the UK–Gibraltar run, where it was very much exposed to attack from both aircraft and U-boats based in France. By late 1941, the need to keep ships together as a group was appreciated, as was the need for training both as units and as a group. Walker would insist on training in harbour in such routine, but vital, tasks as the loading of depth charge throwers, introducing competition between ships. He introduced a standard tactical counter to a night surface attack (Buttercup). This was not perfect but was refined on the tactical table at Liverpool as the basis for many tactical ploys. This training began to show its benefits in the prolonged battle for convoy HG76, etc.

In April 1943, Walker transferred to command the 2nd Escort Group. He was now a captain, specially promoted to note his outstanding work, even though he was two years outside the normal zone for promotion. The 2nd Escort Group was to function as a support group to be used to reinforce the escort of a convoy under attack or to act against a concentration of U-boats located by other means. Quite specifically, the group’s task was to sink U-boats and not primarily to ensure the safe passage of the convoy. They could sustain a prolonged hunt once a submarine was detected. This role is not to be confused with the early idea of hunting groups dashing madly about in the hope of finding a U-boat. The support group concept was feasible because there were sufficient vessels to equip such groups as well as the basic convoy escort. Also, it was possible to identify U-boat concentrations by air search, HF/DF and Enigma.

Combined air–sea operations were valuable for a short period. U-boats had been given a heavy AA armament and a group of three boats could put up a lethal barrage, causing Coastal Command casualties in the Bay of Biscay to mount. A group of U-boats on the surface was fairly secure from air attack but if they dived, the aircraft could launch an attack on the point of submergence with a good chance of success. The U-boats’ aim was to hold off the aircraft until they were short of fuel and had to return to base. However, if the aircraft could call on a support group, the situation changed. There was no way that the submarines could fight a surface gun duel with the powerfully armed sloops. If they dived, either the aircraft would score an immediate success or the group would launch a sustained asdic hunt.

Walker was an arch-tactician and managed to turn the most serious drawback of asdic to the advantage of the hunter. By the end of 1943 he had developed his ‘creeping attack’, which he usually called ‘Operation Plaster’. One ship, usually Walker’s own Starling, would maintain asdic contact with the submarine at ranges from 1,000 to 1,500 yards. The U-boat would be reassured by the steady ping that no attack was imminent and continue in an effort to escape at low, quiet speed – perhaps only two knots. One or more of the other ships of the group would then move slowly and quietly ahead of the locating ship. The position of the attackers would be established and when they were slightly ahead of the U-boat, to allow for the time needed for charges to reach the submarine’s depth, a very large number (twenty-six) of depth charges would be released, set to the right depth. It is claimed that no U-boat evaded such an attack and hence Dönitz never learnt of it. It was also so successful that there is no record of 2nd Escort Group’s using Hedgehog, though when Loch Killin joined there was no reluctance to use Squid. In an operation in January 1944, the group disposed of six U-boats, using 634 depth charges (Woodpecker was lost).

It was ‘Johnnie’ Walker’s last operation. On 9 July 1944, he died after a stroke, probably brought on by stress. He was buried at sea from the famous Western Approaches destroyer Hesperus, as his own group was at work under Cdr Wemyss. His achievements are commemorated by a statue at Liverpool Pierhead. As Adm Horton said at the funeral service in Liverpool Cathedral:

Not dust nor the light weight of a stone, but all the sea of the Western Approaches shall be his tomb.

Woodcock. The two twin Hazemeyer Bofors amidships show clearly.