Chapter 6. The Pendulum Swings: August 1942–May 1943

During the latter part of 1941, the principal problem facing the U-boat Command was that of locating convoys. The Atlantic covers a vast area and even a big convoy occupies a very small part of it. The range of vision from a U-boat, even in good conditions – and Atlantic weather was not often good – was small, and cooperation with Luftwaffe aircraft had not been very profitable.

By the time that the offensive off the American coasts petered out in mid-summer 1942, things had changed much in favour of the U-boats. The British Naval Cipher No. 3 had been broken by B-Dienst in February 1942 and most Allied signals in the Atlantic could be deciphered until June 1943. Signals on convoy routing and diversions could be read and even signals outlining Allied beliefs on U-boat disposition. The cipher war was swinging very much in Germany’s favour as Bletchley Park was unable to read the four-rotor Enigma carrying the Triton code (code-named ‘Shark’ by the Allies). This was a very serious setback, but submarines on trial or training used a simpler code so that GCCS could follow a new U-boat until its first operation. After its departure, it could still be tracked by HF/DF, so that its position was known and its intention could be deduced from its movements.

The greatly increased number of U-boats at sea meant that the patrol lines could be extended and the chance of a convoy’s escaping detection even with diversions was small. On the other hand, the increasing number of HF/DF sets at sea gave a high probability that the contact report would be picked up and the position of the sender determined. A surface escort or aircraft would be sent to the position so that the would-be shadower was, if not sunk, at least forced to dive. Once it had dived, its speed would be much reduced; even if only submerged for half an hour it would have lost a distance of perhaps four miles, which would take a considerable time on the surface to recover. In bad weather, the surface speed of a U-boat was only about three or four knots faster than the convoy, itself slowed.

On both sides, the effects of new technology and of training and operational experience were beginning to show. The British introduced the Type 271M 10cm radar from September 1941, which gave an all-round picture of the convoy and surfaced U-boats. It could even pick up a periscope in calm seas. HF/DF sets were comparatively numerous. Once contact was made, the new A/S mortar, Hedgehog, was in general service, Westcott claiming its first victim on 2 February 1942. There were many more escorts and it was usually possible to have both an outer and an inner screen, so that U-boats attempting to shadow could be forced down before getting close. Coastal Command was increasing its patrols in the Bay of Biscay and scoring successes with ASV II radar and the Leigh Light. U-boat Command countered with a radar detector, Metox, which was effective until February 1943, when the RAF introduced ASV III centimetric radar.

The RN was also benefiting from improved training, both of individual ships at Tobermory and of groups by Gilbert Roberts. The latter training emphasised the need to keep a group together, while group coordination was aided by the increasing use of TBS voice radio. The lack of such training showed at first among USN groups and also in Home Fleet destroyers detached to act as support groups. With initial warning from HF/DF, location by radar and a coordinated counterattack, the U-boats were finding night surface attack to be much less attractive. Their problems were compounded by the decision to cut training times for captains and crew in order to man the numerous U-boats entering service. From the outbreak of war up to January 1943, 160 U-boats had been lost and each loss meant the loss of not only a qualified commanding officer but also one or more potential COs from the other officers. It required both skill and determination to attack a heavily defended convoy. An example is the attack on convoy SC118 in February 1943. Twenty U-boats were involved, sinking eleven ships (60,000 tons) and damaging one. However, of the twenty U-boats deployed, only three attacked (15 per cent), six of the sinkings being due to one U-boat (U-402, von Forstner). There was also a lack of skilled hydrophone operators.

Phase 5 of the Atlantic battle. Air cover had improved and the great convoy battles of spring 1943 were mainly fought in the Gap, out of range of aircraft. There were an encouraging number of U-boat sinkings in the Bay of Biscay.

The U-boat force was still plagued with torpedo problems. An investigation of results in the first six months of 1942 showed that only 404 ships sank, out of 806 hits. This was blamed on the lack of a reliable magnetic fuse, as a torpedo with such a fuse would be certain to sink a merchant ship with a single hit. A new magnetic fuse entered service in late 1942. At about the same date a new electric torpedo, T3, and a pattern runner, G7a FAT, entered service. The scene was set for some of the biggest convoy battles of the war.

Surface vessels	53
Aircraft	8
Submarine	5
Mines	4
Accident and unknown	8

The Great Convoy Battles of Spring 1943

This book does not attempt to provide a complete history of these great battles. The intention here is to show how new technology and training worked together to contribute to the outcome.

The New Year of 1943 began very badly. On 3 January an all-tanker convoy (TM1) from Trinidad to North Africa was sighted by U-514, which sank one ship before losing contact. Dönitz moved a group of U-boats to intercept and contact was regained on 8 January. This valuable convoy was weakly escorted – one destroyer and three corvettes – some or all having problems with their radar. Altogether, seven of the nine tankers were sunk, earning Dönitz a telegram of congratulations from General von Arnim, commanding German forces in Tunisia. The Casablanca Conference started a week later and this disaster may well have concentrated their minds.

HX231

An insight into the grim struggle that was being played out in mid-Atlantic in the spring of 1943 can be gleaned from the story of convoy HX231. Most of the convoy sailed from New York on 25 March. There was some interchange off Halifax, giving a total of sixty-one ships for the ocean passage. This was one of the largest convoys sailed up to that time and occupied a space six miles wide and two deep. The escort consisted of Escort Group B7 and was very weak for this period of the war. The leader, Duncan, was refitting, so her captain (Gretton) took command of the group in the frigate Tay. Then there was the ‘long-range’ V&W destroyer Vidette and four Flower class corvettes.² The capability of the escort was further reduced by the lack of a rescue ship. This meant that it might be necessary to detach a scarce escort to carry out rescue duties. It also meant that there was only one HF/DF set (Tay), precluding the use of cross-bearings to locate an attacker. A support group joined later.

Initially, on 1 April, fifteen U-boats were deployed in a line 200 miles long, twenty miles apart, to locate the convoy. One was lost before joining, but on 1 April six more were directed to the attack. At this date B-Dienst were reading British navy cipher without much delay, while Bletchley Park was yet to master four-rotor Enigma. There were indications at midday on 3 April that the convoy had been sighted, while Tay, Vidette and Pink were able to refuel from the tanker British Ardour.

Contact was finally established early on 4 April by U-530 and the U-boats were ordered to attack that night. Tay picked up the sighting report and estimated it as close on the port beam. Vidette was sent to investigate but failed to make contact. German records show that U-530 was forced to dive at this time, so Vidette had some success. By midday, two more U-boats had made sighting reports, both intercepted by Tay. The U-boats both say they were forced to dive, but no positive action had been taken so they must have been forced down by routine sweeps.

At 1451, a strong signal was identified and Vidette was sent to investigate. She sighted a conning tower fifty minutes later (U-594). By 1630, she had radar contact at 6,000 yards, and soon after that the U-boat dived. Some time later, she had asdic contact and dropped a fourteen pattern, which caused some damage. A later Hedgehog pattern scored no hits and she was recalled. Alisma was pursuing another HF/DF report and sighted the U-boat, which dived. By nightfall, five U-boats were in firm contact and others were close.

It was anticipated that the attack would be on the surface, downwind and down-sea, so the escort was concentrated on the port side. Only Pink was on the starboard side and Vidette was still trying to catch up. Both asdic and radar were working on all six ships – somewhat unusual reliability. The weather reduced the performance of both sensors; radar detection was down to about 3,000–4,000 yards.

Just after dark, the convoy altered course 45º to port, returning at 2300 (three hours at eight knots and 45º equates to 5.5 miles off track). The first torpedo hit at 2208 without previous indication. While the convoy was returning to the original course, another ship was torpedoed but was able to maintain convoy speed. The vicinity was illuminated, which seems to have deterred two more submarines from attacking. Unusually, the U-boats were not signalling their intention to attack, as no close signals were picked up by the HF/DF. Snowflake made an asdic contact at 0127 on 5 April and dropped a ten pattern on U-572 without inflicting any harm. Three ships decided that the convoy itself was dangerous. One rejoined next day; the other two were sunk, together with a tanker that was straggling because of engine trouble. It was straggling that was suicidal, notwithstanding the fact that U-boat Command criticised submarine commanders for taking the easy option of attacking stragglers rather than the convoy itself. HF/DF reports were now coming in and it would seem that some boats were deterred by the almost random movements of escorts.

At 0228, Alisma made another contact on radar at 2,000 yards, which dived and was picked up by asdic. A ten pattern caused serious damage to U-564, which had to return to Lorient. Just before dawn, Vidette was moved from station astern to ahead of the convoy in case there were submerged boats planning a dawn attack; there were not. The escort commander was quite pleased with the result; one merchant ship sunk and one damaged was moderate in light of the number of U-boats in contact.

Soon after dawn on 5 April, the convoy was ordered to make an alteration in course, mainly to bring the convoy closer to air support from Iceland (see map). An ambitious air plan had been intended, though emphasising sweeps rather than the more effective escort role. As a result of bad weather and homing problems, much of this support failed to materialise and the first Liberator only arrived just after midday. It immediately sighted U-584 and dropped six depth charges. The submarine was not sunk as was then thought, but played no further part in the battle. U-260 was in the vicinity, too, and dived to avoid air attack.

U-706 had lost contact during the night but the alteration of course brought it into a fine attacking position. She fired two torpedoes, one of them hitting the escort tanker British Ardour, which sank later. Because of poor weather conditions, the attacker was not located. By about 1330, a second Liberator had joined and for about three hours not one signal was intercepted, an indication that the aircraft had forced all U-boats to submerge. The aircraft left at about 1710 and very soon HF/DF began to receive messages – and there were three hours of daylight still to go.

The American-built Captain class began to enter service in 1943, but none took part in the great convoy battles of that Spring. This is Keats, a diesel-engined Captain, probably during work up.

There were still twenty U-boats targeted on the convoy, although not many were in contact. It was decided to repeat the successful diversion of the previous night – 30º to port just after dark, 40º starboard three hours later. For most of the night, the convoy was heading east with wind from south to south-west, so attacks were most likely from the starboard side, at least after the second turn.

The escort commander expected to receive warning of imminent attacks from HF/DF and told his ships that there could be no sustained attacks on a U-boat with the danger of leaving a gap in the screen; just one quick pattern and rejoin. At 2012, U-594 inadvertently surfaced in the middle of the convoy. The CO decided he was too close to fire torpedoes and escaped ahead, where he was picked up on radar by Alisma. The U-boat dived and Alisma dropped a scaring pattern. While she was rejoining, a second contact was made and attacked with a ten pattern. Gretton thinks that this may have been the end of U-635.

Loosestrife made a radar contact at 2120. It was one of those times when everything possible went wrong – lack of reports, wrong setting on the depth charges, etc. Soon after, Tay’s HF/DF picked up more signals and Pink made radar contact with U-270. A ten pattern caused slight damage. Another contact was made by the watchful Alisma at 2150. Then there was a lull until Pink obtained a radar contact and fired starshell, driving off the attacker.

The second turn was completed at about midnight. At about the same time, HF/DF detected a contact on the starboard bow and escorts were alerted. Tay sighted a U-boat crossing her bows only 150 yards away. Tay could not match the U-boat’s turning circle; the guns could not train fast enough and the 4in got off only one round. The U-boat dived at 800 yards and was soon picked up by asdic, whereupon a ‘good’ fourteen pattern was dropped. Tay ran out to 1,000 yards and made contact close to the original explosion. Sounds as of blowing tanks followed by a heavy explosion were heard, with a red glow seen by Tay’s lookouts. The Assessment Committee awarded a kill but study of records after the war makes this unlikely. Gretton compares the verdicts of the Admiralty U-Boat Assessment Committee with German records and finds their judgement to be very accurate overall.

There were numerous reports from HF/DF but the next contact was not till 0310, when Alisma made radar contact at 2,000 yards. The U-boat dived and Alisma attacked, making a rare mistake as only seven charges of her ten pattern dropped. This may have been the end of U-635, whose fate is uncertain. At 0415, Pink made radar contact at the very long range of 4,800 yards. Visual contact was made at 800 yards but asdic contact was lost (probably the determined U-706). There was a HF/DF warning at 0425 of two boats ahead of the convoy, but only U-134 closed and she was unable to reach a firing position because of the unconscious movements of the escorts. At 0500, a merchant ship damaged earlier had to be abandoned as her bulkheads failed.

During the night at least ten and possibly as many as sixteen attacks had been beaten off without further losses. Considering that there were twenty U-boats deployed, this shows how difficult it had become to attack even a lightly protected convoy. They were kept down by aircraft during the day, so that it was difficult to reach an attacking position, while night attack on the surface was almost impossible against centimetric radar. General morale in the U-boat force was still good but attacks were just too difficult for these inexperienced COs.

The morning of 6 April was filthy, with high wind and sea from the south-west, low cloud and visibility down to less than two miles. There were grounds for optimism, since the support group was expected to join soon, as were aircraft. The escort commander did not expect that submarines could maintain contact in such weather but he was wrong; several did keep in contact using their excellent hydrophones. U-boat Command sent an ill-judged signal telling its boats to attack with more determination; it did not help.

The day’s first action began at 0647, when Tay’s asdic operator reported a submarine contact at 900 yards on the port bow. His report was not at first believed but he stuck with it and was proved right, for which he was decorated. It was U-270; as she dived her stern was seen coming out of the water. A shallow ten pattern was ordered but only five charges dropped. It was three hours before U-270 surfaced.

At about 0800, the first Liberator arrived after a difficult four-hour flight. Two more joined shortly after, giving powerful assistance. The support group of four Home Fleet destroyers also joined about this time.³ There was a potential problem, in that the support group commander was senior in rank to the commander of the escort group. Western Approaches rules were that the escort group commander, in close touch with the situation, remained in charge. Thanks to the tact of both officers, there was no clash on this occasion. The support group were lacking in convoy experience but welcome additions to the screen, particularly as two had HF/DF. For no apparent reason, none of the three HF/DF with the escort picked up any signal all day, although shore stations intercepted plenty of signals from the area of the convoy.

The lack of HF/DF reception meant that it was not possible to direct the aircraft on to specific targets but they did very well on their own. At 0942, an aircraft attacked U-584, causing damage that forced her to return home. Shortly after, another aircraft inflicted severe damage on U-592. The first wave of aircraft were relieved by others, and one of these made an attack at 1618 that probably accounted for U-632. The last aircraft left at 1935. Though some eight U-boats remained in contact using hydrophones, there were no attacks during the night. U-boat Command instructed the remaining boats to overtake the convoy during the night and attack submerged at daybreak. A considerable number of HF/DF interceptions were made in the course of the night.

It was the RAF’s day. There was an escort of Liberators and a supporting sweep of four Fortresses. The sweep made one unsuccessful attack but did locate a lifeboat with survivors. A Liberator reached the convoy at 0805, after all-too-common homing problems. It sighted a U-boat (now known to be U-463) at 0919 and dropped four charges.⁴ Another aircraft attacked at 1234, causing no damage; the same aircraft sighted a U-boat while on the way home and, having no depth charges left, attacked with machine guns, forcing the boat to dive. The next aircraft pursued a HF/DF contact at 1710 and dropped five charges. This was the last attack but the aircraft remained till dark. There were a few contacts on HF/DF during the night but these died down as U-boat Command stopped the operation.

There were two variants of the Captain class, a diesel-engined version and a slightly larger and faster type with turbines. The first into service were diesel vessels like Mounsey, seen here in 1944.

The tally was two U-boats sunk for three merchant ships sunk in convoy and three stragglers. At first sight, this may seem much like a draw but this view would be mistaken; the vast majority of the ships and their valuable cargoes reached their destination safely. This was success.

There were lessons to be drawn from the events surrounding convoy HX231. The following discussion blends the escort group commander’s contemporary views with the author’s hindsight.

In many of the individual actions, there is a common pattern. First detection would be by HF/DF, giving at least a general alert of submarines in contact. Usually this contact would locate the transmitter either to a point, given two or more sets, or to a line of bearing, with only one set as in Tay. Such contacts would lead to the need for speed in a proportion of the escorts to run down the bearing, pursue the contact and return to their station. Centimetric radar of the 271 series made night surface attack almost impossible – certainly for inexperienced U-boat COs.

The importance of training both as individuals and as a group was reinforced. A part of the brief period between runs needed to be devoted to training. Even basics such as depth charge drill still needed practice. Conversely, the U-boat arm was reducing training time – and it showed.

Methods of dealing with a surfaced submarine at close range needed a lot of attention (see later sections on ramming, ‘Shark’, etc.). The need for a rescue ship and the danger of straggling were already well-known lessons.

Conversely, the value of unpredictable movements by escorts had not been appreciated. Nervous U-boat captains would keep their heads down. U-boats and their commanding officers were not lacking in courage, but by 1943 an attack on a convoy, either by day or night, was too difficult for these inexperienced officers. Gretton points out that of the twenty deployed against HX231, two were killed during the action, twelve more were killed before the war ended and only six of the twenty survived.

The value of milch cows was recognised but only if contact could be made without giving away the position.

Air escort was invaluable. If U-boats were kept down all day, they could not get ahead of the convoy for a later attack. Homing procedures and communication with aircraft needed improvement, as did their depth charge drill; there were too many hang-ups.

Many of these lessons were already well known by 1943, thanks very largely to the ‘wash up’ meeting after each convoy. There followed a series of similar encounters (see table 6.2).

ONS5

ONS5 was a slow, westbound convoy of forty-two ships. The escort was Group B7, recovered from the battle for HX231. The group commander, Gretton, was back in his own destroyer, Duncan. The corvette Alisma, which had done so well in HX231, had gone for a much-needed refit and was replaced by Sunflower. Two rescue trawlers were a most welcome addition. There were two refuelling oilers but one proved useless as it had canvas hoses, which broke, instead of rubber. The escort met the convoy in the North Channel on 22 April. The first two days were marked by worsening weather, which increased to gale force causing two ships to collide, one of which had to make its way to Iceland for repairs, without escort.

Spragge, a turbine Captain: note the shield on B gun.

On the 24th a Fortress sank U-710, which was lying ahead of the convoy. The weather improved a little on the 27th, allowing Duncan and Vidette to refuel. The next day, a close signal was picked up on HF/DF and it was clear that the convoy had been spotted and reported. U-650 was able to shadow all day and fourteen more U-boats were ordered to join the attack. Several sweeps down HF/DF bearings were without success. At 1830, Duncan and Tay made a visual sighting but the submarine dived and could not be picked up by asdic. At nightfall, there was a strong wind and sea from the port quarter, so the escort force was concentrated in that area. This placing proved sound; Sunflower beat off the first attack on the port bow by U-386, causing some damage; Duncan foiled four on the port quarter and Snowflake countered another on the port beam. It had been a good night, with no losses in the convoy and one or two U-boats damaged.

However, early on the morning of the 29th, U-258 penetrated the screen from ahead and sank one ship, escaping without detection. On the 30th, a number of contacts were attacked without result. Oribi, the first of the 3rd Escort Group to join in support, arrived that night. There were no attacks overnight, mainly because of the severe weather. The conditions caused the convoy to scatter but Liberators did a great job in directing lost sheep back to the convoy. By nightfall there were thirty-two ships in the main body, while Pink was looking after a further four a few miles away.

That night the rest of the support group joined, making five destroyers.⁵ The weather was still too bad for refuelling and Duncan had to leave the convoy, arriving at St Johns with tanks almost empty,⁶ leaving the command to Lt Cdr Sherwood in Tay. Three of the support group destroyers soon followed.

Dönitz had set up a force of thirty U-boats to attack SC128, which passed the submarine line without being sighted. The U-boats were only eight miles apart and it must have been the weather that saved SC128. However, ONS5 was picked up on 4 May to the surprise of both sides. The weather and the distance from bases made close air support impossible but an RCAF ‘Canso’⁷ spotted U-630 ahead of the convoy and sank her. There were many intercepted signals that day and some visual sightings, but no attacks during the day. The night was a different story. Six merchant ships were sunk, keeping the rescue trawlers, Northern Gem and Northern Spray, busy and proving their worth.

At daybreak on 5 May, the escort in company comprised two destroyers of the support group, Oribi and Offa, one destroyer (Vidette) of the escort group, a frigate (Tay) and three corvettes, Pink, Sunflower and Snowflake. The weather had moderated enough to permit some refuelling but during the day four more of the convoy were sunk. Pink’s little group lost a ship, but Pink sank U-192 . The grim situation was relieved only by the promise of the 1st Escort Group’s joining in a day or two.

On the night of 5/6 May, fifteen U-boats were available to attack but fog made visual observation difficult for them, giving the advantage to the radar-equipped escorts. They beat off twenty-five attacks without loss, while four U-boats were sunk or seriously damaged. The next morning, Dönitz called off the attack. In all, thirteen merchant ships had been sunk, but aircraft in support of the convoy had sunk two U-boats, the 1st Escort Group on the way to join had sunk another, and five were sunk by the escort. In addition, two U-boats collided, both sinking. Ten U-boats in one convoy battle – a great, but little-known, victory. There were still two more years of war to come but the U-boat was never again a potential winner.

The main lesson of ONS5 was the need for sufficient endurance in escort vessels. In the interim, better equipment and procedures for oiling at sea were needed. The effect of the weather on the operational capability of both escorts and submarines was also clearly seen.

Also in May, HX237 lost three stragglers but two U-boats were sunk. SC129 lost three ships and sank two U-boats (one Liberator using the Mk 24 mine).

On 24 May 1943, Dönitz ordered the U-boats to withdraw from the North Atlantic.

Technical Developments

It is hard to attribute any particular development to this short period, so the opportunity will be taken to outline two aspects that were of concern throughout the war.

Surfaced Submarines

It was – is – not easy to sink a surfaced submarine even if it was disabled. Only a small arc of the circular pressure hull would be exposed to gunfire, and the impact of a shell would be at such an oblique angle that it would glance off the tough plating without penetration.

In the early years of the war, ramming was seen as a more certain kill. A study in May 1943 showed that of twenty-seven rammings, twenty-four led to the submarine’s sinking. In roughly half the cases considered, the submarine had been severely damaged by depth charges. Ramming an undamaged submarine was not easy, as the turning circle of a U-boat was less than that of most escorts (see chapter 8, table 8.10). Accounts describe a number of unsuccessful attempts to ram but overall figures are not available.

C-in-C Western Approaches was asked what speed was needed for a successful ramming. He replied that fourteen knots was too slow and suggested twenty knots (a speed that many escorts could not reach!). The Director of Naval Construction was asked the same question and replied that the higher speed the better. Damage to the attacking ship was inevitable but did not increase greatly with speed of impact.

Damage was usually serious, with the lower bow wrecked back to, and including, the asdic dome. It is hard to give a precise time for repairs, as other much-needed work would be undertaken while the ship was available, but seven to eight weeks was typical. (It seemed that repairs took five and a half weeks after ramming a damaged U-boat and eight and a half for an intact one.) In at least one case, a destroyer ran over her victim, disabling both shafts in the process, and was later torpedoed while stationary. At least one other ship lost a single shaft.

These figures led to an interesting operational research comparison.⁸ It was found that an escort vessel saved two to three merchant ships per year, so that loss of service during repairs after ramming equated to 0.4 merchant ships sunk. On the other hand, sinking a U-boat corresponded to saving fourteen merchant ships. This crude analysis shows that ramming was most cost-effective.

However, damage to escorts was to be avoided if possible. By the end of 1942 a fuse setting was available for depth charges to explode at fifteen feet. With Torpex filling, the lethal radius was about twenty feet, which made feasible the use of depth charges against surfaced submarines. Ramming was not forbidden but from early 1943 was firmly discouraged.

Other means were tried. During 1944 a number of escorts had Oerlikons in the bridge wings replaced by ancient 6pdrs (see appendix II). Apparently it was thought that the main gun, 4in or more, was too slow to train, but nevertheless the chance of a 6pdr shot holing a submarine seems remote. No example of its use has been found.

Shark

The problem of sinking surfaced U-boats was appreciated and a special projectile, the Shark, was devised, to be fired from a 4in gun. The complete projectile weighed 96lb, was 73.66in long and was fired with a muzzle velocity of 500ft/sec. It was intended to be fired at fairly short range and enter the water short of the submarine. Spoiler rings on the nose helped preserve the trajectory underwater. There was a hardened-steel nose (33lb), which would pierce both ballast tanks and pressure hull before the charge of 24lb of Torpex exploded.

In Operation ‘Deadlight’⁹ six Sharks were fired against U-3514 (Type XXI) at a range of 2,400 feet. The last two hit and the submarine sank in about a minute.

Camouflage¹⁰

In 1939 all Home Fleet ships were painted dark grey, as major warships had been since Victorian black and white was abandoned in 1904. Destroyers remained all black until late in 1915, in the mistaken view that black was ‘invisible’ at night. Once the Second World War broke out, various schemes of camouflage were adopted, very much on a ‘do it yourself’ basis. C-in-C Western Approaches (Dunbar-Nasmith) was an enthusiast and encouraged such initiatives, starting with the destroyers Grenville and Grenade in 1939.

From late 1943 a number of escorts were given ancient 6pdrs in the bridge wings to use against surfaced submarines, as in this photo of the corvette Snowflake. There is no record of success.

Early in 1940, Lt Peter Scott, RNVR was serving in the destroyer Broke, for which he devised a special paint scheme. Peter Scott was not only a keen yachtsman, as were many RNVR officers, but a well-known artist specialising in paintings of water birds, which gave him an understanding of Nature’s camouflage. The C-in-C liked Scott’s design and asked him to design a paint scheme for the ex-American Town class. This became the basis for the ‘Western Approaches Scheme’, though it did not become official until April 1942.¹¹

Scott was insistent that a camouflage scheme would be effective in one condition of lighting only and there should be no compromise. He chose minimum visibility from a surfaced U-boat at night and, to many people’s surprise, a basically white scheme. To break up the outlines there were panels of very pale blue and green. Later in the war, green pigments were scarce and some ships had blue panels only. His aim was to ensure that all parts of a ship that could be seen from a conning tower were pale in colour. In bright sunshine or moonlight the ships might be a little more visible in consequence, although the scheme worked well at dawn and dusk. It was found that Scott’s patterns were also effective against aerial observation, although sightings by aircraft were usually of the wake.

Western Approaches painting was used by a number of ships not in that command, eg Hunt class destroyers, Halcyon class minesweepers and some trawlers. Wartime paints had a simple oil base and did not adhere well in Atlantic seas, particularly when applied to wet or dirty surfaces, and model-makers interested in the period are recommended to incorporate a generous measure of ‘rust’ in their work.

There is no way of telling how effective this paint scheme was in the U-boat war. Certainly, there are plenty of reports that ships so painted were harder to see but usually there was no basis for comparison. It may be that the value was mainly psychological, crews feeling that something had been done to make them invisible.

Captain Class Frigates (American DE)

The concept of these ships had two starting points: USN views on a cheap destroyer and the somewhat differing views of the RN on an ocean escort. The early studies showed that rate at which a cheap version of a first-line warship under design loses capability is much greater than that at which cost is reduced. Even the might of US industry was overstretched and the design of the DEs was heavily constrained by limits on machinery and weapon supply. Despite these problems, the several groups of destroyer escorts form the most numerous class of warships ever built – and a very effective class.

The USN Studies¹²

Until about 1937, the USN had no requirement for a cheap vessel of destroyer type. There were a large number of the old ‘flush deck’ type for ocean escort, supported by PC boats for coastal work. By 1939, there were doubts as to whether the big fleet destroyers could be built rapidly in the numbers thought to be needed and proposals were made for a simpler vessel. An armament of four guns (3-, 4- or 5-inch) with forty-eight depth charges and a speed of twenty-five knots was envisaged. Endurance of about 6,000 miles at twelve knots and good sea-keeping were required and it was hoped to keep the displacement under 1,200 tons.

The Farraguts were only 1,400 tons, so 1,200 seemed a reasonable target; but it was not to be, mainly because the older ship did not have unitised machinery. The Bureau of Construction and Repair argued for more ships of the 1,630 class, on the basis that there would be savings in lead time. The introduction of a new class will always need considerable investment in drawings, mock-ups, tooling, etc. In addition, some of the knowledge gained in building an earlier class will be irrelevant and experience will have to be built up on the new design (the ‘learning curve’). In the summer of 1940, Gibbs and Cox prepared a design study and President Roosevelt wanted four prototypes built. Adm Stark (CNO) joined in with an all-too-common demand for a much heavier armament on a smaller ship, just as the Bureau began to think that 1,200 tons was insufficient for the lighter armament. Several schemes were tried but the most promising was estimated to cost $6.8 million, as against $8.1 million for a 1,630-ton first-rate destroyer. By February 1941, the most favoured scheme was Study B, a ship of 1,125 tons (standard), with a speed of twenty-four knots and mounting two 5in/38-calibre guns.

Above and below: Aylmer, a turbine Captain. Note the addition of an RN whaler in the later picture (below).

Cochrane and the British Connection

The head of preliminary design in the Bureau of Ships (BuShips) was now Capt E L Cochrane. He had been to the UK for some time in the autumn of 1940, studying British ideas. He was made welcome by the DNC, Sir Stanley Goodall, who had been attached to the Bureau of Construction and Repair during World War I, where he had met Cochrane. Cochrane liked the British Hunt class, although he realised that they were not suitable for USN purposes because of their short endurance. He picked up ideas such as an open bridge on A/S ships and the value of torpedo tubes (fitted in the Type III Hunt class) as a weapon against surface attack.

On 23 June 1941, the British delegation in Washington sent a formal request to the Secretary of the Navy for 100 escort destroyers. Outline requirements were for a speed of at least twenty knots, a length of 300 feet (for good sea-keeping), a dual-purpose gun armament and an open bridge. The DE design seemed very much what was wanted, although there was some opposition on the grounds that a British programme of DEs might cause delays to the USN programme of fleet destroyers. When the USA entered the war, the RN programme was subsumed into that of the USN. In total, seventy-eight DEs were lent to the RN. In fact, the great majority of both RN and USN DEs were built in yards not involved in destroyer-building. In all, 1,005 ships were authorised for the USN and allies. In the spring of 1944, this was cut back to 600 and later to 565. The number actually completed was 498, of which 306 completed by the end of 1943. It was a wonderful achievement.

Lawson, a diesel-engined Captain, was another ship with a shield on B gun. This was the only gun manned during cruising watches, giving the crew a modicum of shelter. It also enabled rocket flares to be used from launchers mounted on the sides of the gun-shield.

There were, however, real bottlenecks in the supply of major items of equipment. It was intended that all DEs should mount two 5in/38-calibre dual-purpose guns and all had the stability (beam) to carry these guns. However, the weapon was in short supply and priority was understandably given to major warships and, later, to USN DEs. The DEs had only limited fire control equipment and even the excellent 5in gun would not have been very effective in AA fire. All early DEs, RN and USN, completed with three 3in/50-calibre guns. These were of little value in either AA or A/S use, as their shells were unlikely to penetrate the tough and well-rounded pressure hull of a U-boat. This armament was lighter than that intended and contributed to the excessive metacentric height, making them unduly stiff and leading to their rolling problems (see chapter 8).

Machinery was an even bigger problem. It had been originally envisaged that they would have twin-shaft, geared turbines with a total of 12,000shp, but there was a shortage of gear-cutting machinery. Gear cutters are complicated machines; it would be some time before they were available and an alternative machinery plant was needed. There seemed to be a solution in the diesel-electric plant used in USN submarines, where each shaft had two 1,500bhp General Motors V-12 diesels driving generators to a 3,000hp electric motor. Four diesels per shaft would provide the power needed for a fast DE from well-proven units. Fitting diesels meant lengthening the ship by three and a half feet and an increase of 130 tons in displacement. However, it was subsequently realised that the diesels, too, were in short supply and consequently it was decided to fit only two diesels per shaft for a combined total of 6,000bhp and a loss of about four knots in top speed. These became the USN Evarts class (GMT – GM Tandem Diesel). Thirty-two of these ships were lent to the RN.

The next group of DEs had 12,000shp turbine machinery driving through generators and electric motors, which added twenty feet to the length, two feet to the beam and 200 tons to the displacement; the extra length was beneficial to speed and helped them to reach at least twenty-four knots. Forty-six of these ships (USN Buckley class TE¹³) served in the RN.

The earlier groups of DEs had the open bridge desired by the RN, with an asdic hut let into the forward side. The hull was flush-decked with considerable sheer to give adequate freeboard forward. They had a long, continuous superstructure from B to X gun. Internally, they were fitted out to USN standards and were far more comfortable than contemporary RN ships, discussed later under the Colony class.

They all mounted three 3in guns, and many had one twin Bofors and upwards of five Oerlikons as completed. The British ships had four depth charge throwers and two rails (ten pattern). They were also given two special rails for launching the ‘one ton’ depth charge Mk 10. Initially, they had 112 depth charges but this was increased to 160 as part of the measures to reduce roll. By the time they completed, Hedgehog was available and fitted abaft A gun. Type 144 asdic was fitted in most, though some had 128D, which could be updated to 144. A few had Type 147 installed.

They had twin rudders behind the twin propellers at the suggestion of William Hovgaard, which model tests showed reduced the turning circle by some 25 per cent (see chapter 8), very important in depth charge attacks.

The design was developed by Gibbs and Cox, concentrating on ease of production. They were all-welded mild steel, built in prefabricated sections. The majority of the shell and deck plating was quarter-inch, with half-inch for the garboard strakes. Superstructure bulkheads were only three-sixteenths of an inch. This structure proved largely trouble-free in service. The all-welded hull with its freedom from leaks was welcomed by the crews. Delivery began in January 1943 with the diesel ships ahead of the turbines. A total of 24 entered service in 1943 and 54 in 1944. Table 6.3 shows the technical specifications of the class as built; note the fuel economy of the diesel ships.

	Diesel (32 ships)	Turbine (46 ships)
Displacement, deep, standard (tons):	1,450, 1,150	1,840, 1,300
Dimensions (feet):	289½ x 35 x 10¾	306 x 37 x 12½
Shp and speed (kts):	6,000 = 20	12,000 = 24
Fuel (tons), endurance (miles) @ (kts):	198, 6,000 @ 12	350, 6,000 @ 12
Complement:	198	220

Curzon, a turbine Captain with a very heavy AA armament. As well as the twin Bofors aft she seems to have singles forward of the bridge and at least eight Oerlikons.

RN Modifications¹⁴

Modifications carried out in RN ships were initially comparatively minor. Torpedo tubes were omitted in all, with the intention (initially not fulfilled) of fitting more anti-aircraft guns. B gun, which was manned in cruising stations, was given a spray shield, enabling rocket flare launchers to be fitted. Many more Oerlikons and some single Bofors were added as they became available. Those ships employed on east coast duties were given a 2pdr pom-pom on the stem as an anti-E-boat weapon. Snowflake flares were fitted on the bridge wings and smoke floats were carried on top of the depth charge rails. Most had a HF/DF aerial at the masthead. A crow’s nest was fitted on the mast. A twenty-seven-foot whaler was carried in standard RN luffing davits on the port side. Other additions included oiling fairleads, extra life rafts and improved wind screens.

Other, more extensive modifications were considered but not implemented. The first such scheme involved mounting 4.7in guns in place of 3in. Later ideas involved twin 4in in place of A and X, and 3in with a twin Squid (twenty-four salvoes) in place of B gun, with 144 and 147 asdic. Six twin and four single Oerlikons would be mounted. An AA version would have had three 5in DP guns with a Mk 50 director, three twin Bofors and four single Oerlikons. Only twelve depth charges would be carried, with 128 asdic. Three TE were converted to coastal force control and three GMT to LSH(S). Five were planned for conversion to fighter direction ships. Five others were being converted to floating electrical power stations at the war’s end. Of these, Hotham was retained, with the intention to use her as a gas-turbine test bed, but this never came about.

It was intended to replace one of Hotham’s steam turbines with a gas turbine, leaving steam on the other for comparison, the electric drive making the connection straightforward. The chosen engine was the English Electric EL60A. Steam turbine technology was employed for long life, making the plant big and heavy. The EL60A ran shore trials in late 1951 but it had become obvious that this was not the way to go and the project was abandoned in 1952. Hotham was returned to the USN in 1956 and scrapped.¹⁵

Five GMT and two TE were lost, and three GMT and seven TE damaged beyond economic repair (presumably because so many new ones were coming into service).

Speed of the Captain Class

There were actually two Captain classes: one with diesel-electric propulsion (GMT) and a speed of twenty knots, the other with steam turbo-electric propulsion and a speed of twenty-four knots (TE), with identical weapon and sensor fit. In their analyses of U-boat sinkings by escort class, both Brown¹⁶ and Collingwood¹⁷ treated the two classes together, noting that the combined total of sinkings was rather higher than would be expected from their equipment (Hedgehog, depth charges and Type 144 asdic). A simple attempt to separate the two classes came up with some interesting statistics: ‘The thirty-two diesel ships were involved in nine sinkings, the forty-six steamers in seventeen, with three sinkings involving both types.’

The analysis was crude and included all sinkings – English Channel and Arctic, as well as the main Atlantic battleground. However, the results are consistent with accounts by authors such as Macintyre,¹⁸ who commanded a mixed group of three diesel and three steamers. Almost always, it was a steamship that would be detached to prosecute a target, as the four knots of extra speed reduced the time needed to rejoin.

The difference between the classes becomes even more remarkable when it is noted that five of the diesel ships’ seven successes came in 1943 (or January 1944), before many steamers were worked up.

The need for a significant proportion of escorts to have a relatively high speed is clear. Two hours behind a seven-knot convoy takes fifty minutes to catch up at twenty-four knots, sixty-five minutes at twenty knots.

The Colony Class Frigates¹⁹

In 1942, the USN was anxious to build even more escort vessels. It was thought that some yards in the USA would have difficulty in building DEs, with their more complicated structure, but could build to merchant-ship style. The British River class was selected as the basis for these new ships and the famous design agency Gibbs and Cox was chosen to develop the design. They were originally designated as gunboats (PG) but in April 1943 all were reclassified as frigates (PF). In all, 100 were ordered, of which twenty-one were transferred to the RN (PF 72–92).

The Colony class, such as Antigua shown here, were an American adaptation of the British Rivers. By the time they entered service their technology was dated.

Displacement (tons): 1,509, 2,238 deep

Dimensions (feet): 285½ pp, 304 oa x 37½ x 13¼ deep

Shp and speed (kts): 5,500 = 20 (18 continuous)

Fuel (tons), endurance (miles) @ (kts): 768, 7,300 @ 11; 6,400 @ 14; 5,270 @ 16¼; 3,000 @ 19

Complement: 120

In the redesign, beam was increased by one foot, and two and three-quarters feet added to the length amidships to accommodate the longer US machinery. This consisted of two Babcock and Wilcox three-drum boilers delivering steam at 250psi to two four-cylinder triple-expansion engines. Despite the increase in size, the hull weighed fifty tons less than that of a River, as a result of its all-welded construction.

Armament consisted of three 3in guns, four 40mm Bofors and six single Oerlikons. They had a Hedgehog, four depth charge throwers and two rails, with US Navy SA (air warning) and SL (surface) radars. Late in the war, it was proposed to convert the whole class to air warning ships, for which role they would have had a Type 277 set aft and a fighter direction office at the foot of the foremast. Only Caicos completed the conversion.

The twenty-one British ships formed the total output of the Walsh-Kaiser yard at Providence, Rhode Island. Virtually the whole class suffered severe machinery problems on build. Monsarrat states that his ship was delayed for eight months by these problems, running fourteen sets of trials.²⁰ Whatever the problem was, the cure seems to have been complete, as there were few complaints after the vessels’ entry into service.

The USN had three areas of concern, reviewed by Johnson.²¹ They were said to be structurally weak, which seems unlikely. They did suffer from cracking at the numerous sharp corners of openings, which would spread easily in their welded structure. They had a much larger turning circle than the DEs, with twin rudders. Finally, they were said to have inadequate ventilation, a complaint upheld by Johnson, who served in PF 40. This seems unlikely in the light of the RN plans to convert them for Pacific duties. Perhaps the USN views on ventilation differed from those of the RN, where the louvres were often stuffed with an old pair of socks!

Dominica, another Colony. By British standards they were luxuriously equipped.

It was intended to fit the whole Colony class as air warning ships for the Pacific but only Caicos was completed as such. Note the 277 aerial abaft the mainmast.

On the other hand, the RN crews were delighted with their ‘luxurious’ accommodation. Monsarrat gives a most interesting comparison when the crew of a River were transferred en bloc to a Colony.²² The equipment to USN standards included a laundry (Warrior had a laundry in 1860), ice-water dispensers in each mess deck, dish washers, potato peelers, ice cream machines, typewriters and two cinema projectors. There was an internal communication system with loudspeakers in each mess deck and a telephone system with an exchange. There were no voice pipes – the captain had a microphone round his neck. None of this impinged on safety: the furniture was all-metal, there were no rugs or linoleum and the few door curtains were of fibre glass. There were no side scuttles.

Deliveries began late in 1943, by which time their A/S equipment was dated and U-boats were scarce. They may be seen as a little better than a River but inferior to the Lochs. They claimed two and a half sinkings.