‘I wish I’d never joined for a sailor, mother dear,
I’ve seen some places in my time but nothing like this here,
The girls won’t let us court them and the canteen’s out of beer,
And that’s what it’s like in the Navy’
That’s what it’s like in the Navy‘ Trad
At 11:00 hrs on the diamond sharp morning of Sunday 3rd September 1939, the Admiralty sent the following message to all warships;
‘COMMENCE HOSTILITIES AGAINST GERMANY IMMEDIATELY’
The Submarine Spearfish received this communication while patrolling off Egersund in Norway, a look-out on the bridge reported a white trace heading towards the boat. Without a moment to lose, the officer on watch called diving stations;
‘DIVE DIVE DIVE’
In the control room below, the helmsman pressed a klaxon which sent the forty strong crew into a state of frenzy. It took four seconds for the look-outs to clear the bridge, leaving the officer on watch (always the last man down) to securely clip the hatch before joining them. Already Spearfish was diving.
When the klaxon sounded, the engine room watchkeepers obeyed the internal telegraph system. They first stopped the main diesels then wound out both engine clutches, thus isolating the engines from the screws. While submerged, propulsion depended upon the motors. Next the muffler tanks were shut off to keep exhaust emissions free from tell-tale smoke as the boat dived. In the motor room and huge switches fed power to the main motors while rheostats checked their speed.
Upon hearing the alarm the control room messenger rushed over to the diving panel to open the main vents prior to placing the aft hydroplane controls in the ‘hard a dive’ position ready for the coxswain to take over. Already the officer on watch was giving his breathless account to Captain John Eaden. The two officers were surrounded by men fumbling, skidding and cursing in a headlong rush to vegetables. The angle of the deck testified that Spearfish was diving deeply now. The expression on ‘Nit’ Eaden’s face indicated this was no drill. Eight seconds into the dive, Lt Donald Pirie, First Officer, levelled the boat off at periscope depth.
Confirmation that this was indeed the real thing came in the form of a noise, barely audible at first but which soon grew in intensity. The torpedo passed harmlessly ahead of the boat. The crew of Spearfish lived to fight another day, their survival due to a combination of efficient reaction and good luck.
The ASDIC operator reported hearing strong hydrophone effect (HE – the sound of screws cutting through water. Now the initiative had passed to Spearfish as Eaden scanned through the Barr and Stroud search periscope for signs of the attacker. The bow tubes of Spearfish were open and at a state of readiness. The sweep revealed nothing but an empty Autumnal sea. Six hours later and with no further signs of the enemy, Spearfish surfaced and continued her patrol .
Spearfish was the first British submarine to see action in World War II. She was to spend most of her harrowing but eventful war operating from Blyth in Northumberland. Spearfish had left base at Portland in company with Sturgeon and Swordfish on 23rd August to take up war stations at Dundee, only to be diverted to patrol off Norway on 25th August. Portland was the peace time home of the 6th Submarine Flotilla.
As Anglo-German relations deteriorated, so Admiralty planned to concentrate all submarines around the depot ships Forth and Titania at Portland prior to taking up East coast war stations at Dundee, the Forth or Blyth. Some boats were dispatched to patrol the Ystebrod (or Obrestad) reconnaissance line, the remainder sailed on 23rd August. Given that war with Germany had been anticipated since 1934, war stations had been earmarked for some time. HMS Forth and her ‘S’ class boats was set to form the nucleus of the Second Flotilla at Dundee. The ‘T’ class boats, the most powerful of British submarines were bound for Rosyth and the Forth. The Blyth bound elements of the Sixth Flotilla comprised Unity (Lt. J. Brown), Ursula (Lt. Cdr. G. Phillips), Undine (Lt. Cdr. A. Jackson), L26 (Lt. Cdr. F. Lipscombe), L27 (Lt. P.J. Cowell) and H32 (Lt. R. Jenks). Captain Michael Lumby DSO, DSC, MID, then Navigating Officer on Sturgeon recalls:
‘We presented a fine sight on our way up the East coast. Seven submarines in line ahead with Titania following rather slowly behind in her own time’
Off St Mary’s Island the Sixth Flotilla boats altered course for Blyth with the intention of entering harbour one by one. The submarines may have looked impressive but appearances can be deceptive. Half were obsolete while the remaining three had not been designed to fire a torpedo in anger. The Sixth Flotilla was after all a designated training unit. The Submarine Service was reduced to operating bargain basement hardware in what was acknowledged to be one of the key theatres of the undersea war. The submariners of 1939-40 were paying the price for Admiralty neglect, political myopia and public abhorrence.
For the generation who lived through the Great War, the word ‘submarine’ evoked the same horror carried by ‘The Bomb’ today. It conjured up the dreadful Lusitania affair, it brought home images of cold-blooded attacks on hospital ships and innocent merchant vessels. None could argue against the efficiency of the submarine however.
By 1917 U-boats were claiming half a million tons of allied shipping every month. While the High Seas Fleet lay bottled up in the Jade Basin, some, including Jellicoe, thought the U-boat was coming perilously close to winning the war all on its own. Unlike dreadnoughts, submarines were cheap to build and economic to operate. A submarine could range undetected for long distances in waters inaccessible to other warships. The submarine was versatile. When not hunting it could provide useful reconnaissance information. The submarine was one of the most lethal weapons in the arsenal. If this lesson was not lost upon German strategists, the British establishment continued to regard the submarine with disdain.
Unlike the Germans, the Admiralty had not developed a separate submarine strategy during the Great War. Submarines based in Blyth, were regarded as mere appendages of the Grand Fleet. When allowed freedom to operate, the results could be impressive, whether in terms of attacking enemy warships or gathering intelligence on High Seas Fleet activities. Nevertheless general service aversion towards the submarine ran wide and deep. Unsurprisingly the Submarine Service was the Cinderella branch of the royal Navy. The oil stained, gleam-eyed submarine officer had the look of a fisherman who had been at sea for far too long. Indeed the submariners were proud of their subversive image and did their utmost to live down to their reputations.
By 1918 a war-weary Europe sought lasting peace. The Washington Naval Treaty of 1922 and the London Naval Treaties of 1930 and 1936 were designed to constrain submarine warfare by introducing strict (and unrealistic) rules governing submarine attacks. Henceforward submarines must only attack other warships. The interception of merchant vessels was to be controlled by a code of practice detailing the steps that must be taken. The rise of Hitler was years away and the signatories might be forgiven for their enthusiastic naivety. With social cohesion threatened by a moribund world economy, politicians of the period had more than enough problems on their hands as successive governments attempted to alleviate the effects of mass unemployment with expensive social programmes. In this climate there was widespread support for the slashing of military budgets. Disarmament may have been in tune with the zeitgeist but tragically its heyday in the thirties would coincide with the zenith of German re-armament.
Only as late as 1930 could a start be made in replacing the ageing ‘L’ class boats with new coastal submarines designed for work in the North Sea. Named after fish or marine animals, the first group built at Chatham Dockyard between 1930 and 1933 comprised Sturgeon, Starfish, Seahorse and Swordfish. The order for the next batch, Sealion, Salmon and Spearfish was awarded to Cammell Laird in Birkenhead. The subsequent orders for Shark, Snapper, Sterlet and Sunfish went again to Chatham but Scotts of Greenock built Seawolf in 1938. The burden of North Sea patrols would fall upon these submarines and only three would survive the war.
Sufficient resources had been channeled into submarine detection for the Allied Submarine Detection Investigation Committee to develop an underwater device capable of detecting the range and direction of an enemy vessel. It was not a foolproof system. Differing water densities, wrecks, fish shoals and shrimps (which produced a disconcerting clicking noise) all gave confusing signals but in the hands of a skilled operator the results of ASDIC could be impressive. From 1932 sets were installed in nearly all British warships. ASDIC was to play a key role in winning the war at sea.
A school for anti-submarine (A/S) training was established at Portland under the aegis of HMS Osprey in 1924. From 1927 the curriculum included ASDIC instruction. The only problem was a shortage of submarines to practice upon. As a re-arming Germany inspired by an aggressive ideology became a reality, so the government reluctantly funded the construction of three purpose-built ‘clockwork mouse’ submarines; Unity, Ursula and Undine. Built at Vickers Barrow yard, they were small, cheap and in keeping with their role, totally devoid of armament. After all the Sixth was a training flotilla designed to provide general service (the surface navy) with experience of hunting real submarines . The obverse, of training submarine crews in evasion techniques and attacks, was never a priority. The submarines were there to mount simulated attacks upon warships conducted according to pre-arranged time tables. A sad litany of submarine disasters, the results of accidental rammings had plagued the inter-war years. In recognition of their vulnerability the submarines were ordered to depart the exercise zones before nightfall. These ‘ping-running’ exercises provided priceless experience for general service ASDIC operators but they did little to prepare submariners for realities of the forthcoming undersea war.
In 1939 it was decided to add six torpedo tubes to the ‘U’ class boats. With space at a premium, these tubes were fitted externally outside the pressure hull, resulting in a pronounced bow snout. This feature tended to create a tell-tale wave should trim be lost while firing torpedoes.
Submarines operating in the North Sea came under the jurisdiction of the Commander in Chief, Home Waters (C. in C.). In theory Britain had overwhelming naval superiority in this sector, stretching from Gibraltar to the Arctic [Fig 1] but a combination of ageing hardware, poor speed and reduced armament, undermined efficiency.
Responsibility for submarines in Home Waters rested in the person of Rear Admiral Submarines (RA(S) Bertram Watson DSO, appointed to this role in December 1938 . Formerly the responsibility of RA(S) was purely administrative but following the declaration of war, the responsibilities of RA(S) were extended to include operational matters. Prior to this juncture tactical control of submarines was in the hands of Flag Officer, Home Fleet. Watson was required to formulate submarine operations in accordance with the requirements of C. in C. Home Waters. This’ expansion of responsibilities did not bring a commensurate increase in resources. Watson had to build his staff support from scratch.
Admiralty was itself accountable to political masters and in 1939 the government appointee as First Lord of the Admiralty was Winston Churchill. Churchill had not been popular with the Royal Navy as the memoirs of Cdr. R. Turner testify:
‘In 1908 Winston Churchill the Liberal candidate for Dundee made it known he in wanted to go out in a submarine and C23 was detailed. The ‘Dundee Club’ put a subscription list up for the commander of a submarine who would drown WC. When the list reached £600 the notice was taken down as ‘becoming too dangerous ’
So these were the men who devised the strategies and tactics of the undersea war in the North Sea but what were their options and limitations ? Practice was shaped by First World War experience .
The German war machine was known to be heavily dependent upon shipments of iron ore imported from Sweden but shipped out of the Norwegian port of Narvik. If this line could be broken, as it had been during the Great War blockade, the enemy would soon face crippling shortages.
Submarines based at Blyth were equidistant from Helgoland and the Skaggerak [Fig 1] the heart of German sea-space. The 11th Submarine Flotilla, under the direct control of C. in C. Grand Fleet, had become operational at Blyth in December 1916. Its primary role had been to co-operate with the Fleet in grand set piece operations which somehow never came to fruition. When off the leash the Blyth boats patrolled seaways off the Danish and German coasts, they had gathered crucial intelligence and delivered occasionally successful and spectacular attacks upon German warships. Wilhelmshaven with its naval facilities and the Jade basin opened into the Helgoland Bight and enemy ships attempting to break out would were equidistant first have to steer North up the Jutland coast then follow the Norwegian seaboard before setting a Westerly course for the Denmark Straits. Submarine boats based at Blyth, the Forth and Dundee would be well placed to wreak havoc, much as their fathers had done in the Great War. Unlike their fathers, this generation of submariners would face an enemy armed with working listening devices, accurate depth-charges and in time, the overwhelming benefits of air superiority. The greatest danger however was posed by sea-mines.
Admiralty staff had long predicted this move. There were even certain advantages in that any capital ships attempting to break out would be funnelled through a predictable corridor between the Eastern edge of the GDM on one side and the Jutland/Schleswig-Holstein coast on the other. The formation of the GDM enhanced the value of Blyth as a submarine base but it did make journey times significantly longer as a direct route to the Bight was now out of the question. Until a passage could be found through the GDM the only feasible approach was from the North.
Admiralty staff plotted the position of the GDM on charts then divided the corridor thus formed into two sectors [Fig 2]. Zone E lay between the minefield and the coast of Denmark. Zone B was South of a line drawn N 55º 10. To the German coast. This was the most promising and by implication, the most dangerous sector. While submarine commanders were to be provided with the latest intelligence with regard to approach/withdrawal routes in Zone B, the question as to whether to make an attack or how far to approach the German coast was left to the judgement of the individual skipper. A blow struck in these waters would not only cause material damage, it would be of inestimable propaganda value, yet to pursue these operations was tantamount to sending men into the most fiercely guarded stretch of sea in Europe.
For some weeks prior to the outbreak of war the Nazis had been sowing a vast minefield designed to protect the flank of Helgoland approaches from British probes. This minefield stretched from the border with Dutch territorial waters to Lim Fjord in North Denmark. The Germans knew this minefield as the Westwall. It comprised of surface and invisible anti-submarine (A/S) minefields laid at various depths in a series of overlapping strips. Aware of the imperative to pacify neutral minds, the Germans openly declared this minefield, henceforward known to the Admiralty as the GDM or German Declared Minefield.
Admiralty staff accurately predicted that the first move on the part of the enemy would be a warship breakout into the Atlantic. As a counter, Admiralty required accurate reconnaissance but the ageing Anson aircraft of Coastal Command had not yet been replaced by the superior Hudsons. Submarines allocated to the 2nd Submarine Flotilla would have to improvise until late September until the RAF could take over. A line was drawn running South Westwards from the Norwegian town of Ystebrod . It was planned that the submarines should be on station a full implication week before hostilities commenced. Meanwhile the 6th Submarine Flotilla was getting to know Blyth.
Commander (later Captain) Jocelyn (Jock) Bethell ran the 6th Flotilla according to the directions of RA(S). He knew Blyth well, having served there in the Great War. The depot ship Titania moored at the same quay she had used twenty two years earlier. It was said that when she finally weighed anchor in October 1919, she could not get underway because of the amount of ‘gash’ tipped alongside. It was just like old times.
The grimy if versatile old ship’s holds held everything required to set up a submarine base. There were plumbers, coppersmiths and carpenter’s shops, heavy and light machinery shops, electrical repair units, torpedo workshops, torpedo storage magazines, plant to charge submarine batteries, fuel tanks, crew accommodation and messes, lockers, showers and a well stocked wardroom for the officers. Titania contained everything required to sustain her motley brood of submarines and their crews. Bethell sought to move as many of these facilities ashore as soon as possible. With rumours circulating that all submarines were to sail on patrol as early as 31st August, there was not a moment to lose. ERA Alan Smith describes the scene:
‘We proceeded to open up the base a week before war broke out. Our main workshops were situated in the Ice House by the Harbour. Our own shipwright’s workshop was in one of the dock sheds en route. Bitterly cold, in the past it had been used to store fish, the memory of which lingered ’
Working under the guidance of Engineer Commander ‘Wimps’ Davis. Alan Smith and his team set about turning the Eastern basin into an operational submarine base. Huts were partitioned and rudimentary heating installed. Lathes, drills, torpedo racks and latrines were introduced. Cdr. Davis observed:
‘At first we had about as much equipment as would mend a bicycle but from practically nothing we built up sufficient workshop capacity to maintain the Flotilla in good order until the end of the war’
Bethell was forced into an uneasy compromise with vested interests also using the Harbour, including local fishermen and in time, an RAF rescue launch. Blyth was a major coal exporting port and there was constant movement of colliers in the River Blyth, either delivering their loads at the staithes or heading downriver in ballast to join one of the FS convoys in the Swept Channel. Many of the ships belonged to neutral countries and they represented a distinct security risk for submarines heading to or from Blyth Docks. It was in the national interest that Blyth staithes should remain operational and this outweighed any fear of spies.
Upon arrival at Blyth the half of each submarine crew designated ‘watch ashore’ was directed towards the grandly titled ‘Wellesley Nautical School’. Up the harbour road they trooped in search of their billets, steaming bags thrown over shoulders, hats perched at a jaunty angle. They might have been forgiven for thinking they had arrived at the wrong place. Generations of locals knew it as ‘The naughty boys school’, it was a reformatory institution, half created from a spirit of Victorian philanthropy, half as a handy pool of cheap maritime labour. Just before the start of hostilities the inmates had been decanted elsewhere and the submariners moved in. The School was suited to its future role, being spacious with ample scope for expansion. There was a sturdy perimeter fence to deter intruders.
Fronting the coast road on the ‘Quarter Deck’, adjacent to the entrance, stood a figurehead of Admiral Boscawen, said to have been removed from the original hulk destroyed by fire at North Shields at the turn of the century. One building was turned into the Wireless Transmission Office. A teleprinter was installed to keep Bethell in contact with RA(S) Watson’s HQ at Aberdour in Fife. Initially the officers were none too happy with the accommodation provided for them and preferred to remain onboard Titania. Some moved into the concrete yacht in the South Harbour. In time a comfortably furnished wardroom was opened in the ‘H’ shaped Adminstration Block and furnished cabins installed.
Within the compound stood a number of regulation sized huts which had been used by submarine crews during the Great War. Each crew was given its own hut complete with iron bedsteads, lockers and latrines. Visualizing a Northern Winter in these spartan conditions the men fought for the beds nearest the stoves. The quality of accommodation varied according to the status of the individual. POs and ERAs could select from a number of small but comfortable bungalows. Junior and senior rates had separate messing arrangements but there was a large general canteen.
The Royal Navy offered little help to couples. The married man, officer or rating was left to his own devices when it came to finding accommodation for his wife and family. Adverts for rooms placed in Blyth and Seaton Sluice met with an overwhelming response from locals.
Security was of paramount importance and a contingent of Royal Marines joined the local police in guarding the South Harbour and its approaches. Overnight the Harbour and huge swathes of the coast, became places of mystery to locals. Access roads were blocked, gates disappeared behind sandbags, machine gun posts ringed with barbed wire were installed, huge canvas screens limited views. There was close liaison between the base, the Blyth Harbour Commission and Blyth Docks in general matters but when it came to submarine movements, Captain Bethell and his staff divulged as little as possible. This information was of course top secret.
As a response to speculation that Deutschland and Graf Spee would break out from the Helgoland Bight, Watson decided to station an arc of submarines between Terschelling and Horns Reef in the hope of intercepting them (unbeknown to Admiralty these ships had actually already sailed on 24th August). Watson intended to commit nearly all the Blyth submarines to this operation. H32 was the exception. She would keep watch outside the GDM in Zone A. The rest would enter the Helgoland Bight. On 31st August. Bethell waved them off on their first wartime patrols. First came the long haul across the North Sea. Allowing for a fast surface passage, it would take an average of three to four days to reach the mouth of the Skaggerak, or the Northern limit of the GDM, before heading South to the Bight and their respective billets or patrol zones . A patrol might last anything from a week to ten days before the ‘return’ signal was transmitted. An incoming intelligence report might well extend the patrol (indeed following just such a report on 7th September, on 8th September Ursula was ordered to alter course to intercept a convoy heading from Rotterdam to Germany and if possible, to sink the escorts). All being well, twelve miles from the East coast Swept Channel the returning submarine would transmit an ETA signal and the necessary berthing preparations would be made. On 11th September all the Blyth boats were recalled. With the exception of little H32 and Undine, all had been in contact with the enemy.
The first patrol of H32 (Lt. R Jenks) in Zone A1 off the Dogger Bank had been a nightmare for the crew. The boat encountered a force 9 gale. When one of the hydroplanes was damaged it became impossible to maintain periscope depth. The patrol was abandoned and the boat returned to Blyth on 14th September .
L26 (Lt. Cdr. F. Lipscomb) had been allocated a billet in Zone E just outside the GDM. On the morning of 6th September with the boat at periscope depth, two Koln class cruisers were spotted, Konigsburg and Karlsruhe. Both warships had been engaged in adding mines to the GDM and were now heading South at speed. A stern chase was out of the question and the warships disappeared back into the sea-fret . L26 returned to Blyth on 13th September.
HMS/M Unity (Lt. J.F. Brown) was given a billet in Zone B to the South of L26 when she was ordered to close the coast to intercept the Rotterdam convoy. On 8th of September with the boat North of Borkum Island the German gunnery ship Brummer crossed her sights . Once again a stern chase was unfeasible and Brummer escaped unmolested. A significant number of fishing boat lights were noted in this sector. Sometimes the rocking motion of the boat allied to the tedium of staring at a fixed point produced optical illusions. One pair of lights appeared to break away from the rest then grow larger, forcing Unity into an emergency dive. Unity arrived back at Blyth on 13th September.
A short distance from the position of Unity, Ursula was on the surface charging batteries. Lt. Cdr. George Phillips joined his First Lieutenant ‘Robbie’ Alexander on the bridge. Lt. Alexander was a bear of a man who prided himself on his great beard, known a ‘set’ in the Royal Navy. This beard failed to shield him from the driving rain sending rivulets of icy spray dribbling down his neck. Phillips (37) on the other hand remained insulated due to a suit of his own design. Made of oiled canvas, his ‘Ursula Suit’ was long enough to keep the legs warm, while the collar could be tucked inside a balaclava. Unlike clumsy oilskins the suit was flexible enough to allow unrestrained movement. Phillips had written to the Admiralty in the hope that it might be adopted as standard issue but so far to no avail. Lt. Alexander and the look-outs could only shiver enviously. On 8th September a bow wave was sighted. The look-outs identified the stepped conning tower of a U-boat. Phillips turned Ursula on a firing course. At 19:11 hrs the ASDIC operator reported loud HE.
’19:13 hours – Sighted a German U-boat (Oceangoing-type). Started attack.
19:23 hours – Fired four torpedoes from 1,000 yards.
19:26 hours – The enemy was observed to have altered course towards, combing the tracks. It was also seen she increased speed as heavy exhaust smoke was seen. Ursula meanwhile turned for another attack.
19:33 hours – Fired one torpedo. It missed. The target could only just be seen in the fading light.
19:40 hours – Heard an underwater explosion, most likely the torpedo exploding upon the end of run.
19:41 hours – Sighted a second submarine but owing to the darkness it could not be attacked’
The look-outs on U-35 (Kplt. W. Lott) were also alert. The torpedo tracks were spotted enabling IIWO Hans Roters to turn the boat and ‘comb’ the tracks. Nevertheless this had been a close run thing for the U-boat, an attack on its own doorstep. The KTB indicates the sense of shock felt by the U-crew, Lott describes ‘…pale faces on the bridge, including my own. A true baptism of fire…’ U-35 was one of a number of U-boats en route to a patrol in the English Channel . Directly behind U-35 sailed U-21, U-23, U-31 and U-36. One of these was likely spotted by Ursula at 19:41. Ursula reached Blyth on 13th September.
Undine made an uneventful patrol in Zones E and B of the Helgoland Bight, returning to Blyth on 13th September.
As Jock Bethell digested the contents of these patrol reports a couple of issues emerged. The fishing boats in Zones E and B seemed far too curious. They may have been working in tandem with enemy A/S craft. From this point onwards all the submarines were to give fishing boats a wide berth and on no account disclose their presence. Then there were the puzzling accounts of ‘North Sea grunts’ in the Bight sector. Bethell reassured his officers that he himself had heard these noises back in the First World War. Harmless, he said. There was intense wardroom speculation that these noises were caused by everything from underwater volcanic action to flatulent porpoises. The humour masked a lingering fear that the noises were linked to a listening device capable of detecting submarines. The Sixth Flotilla had started the war in an aggressive fashion but the experience of Second Flotilla boats indicated that communications between Admiralty and Coastal Command must be tightened up following a series of bombing attacks made by aircraft against the Dundee boats in early September, culminating in the ETA message transmitted by Lt. Cdr. Gregory of Sturgeon,
‘EXPECT TO ARRIVE AT 23:00 IF FRIENDLY AIRCRAFT WILL STOP BOMBING ME’
RA(S) was given the responsibility of passing on details of routes and dispositions to Coastal Command and the RAF attacks subsided but events of the 10th September when HMS Triton attacked and torpedoed HMS Oxley, appeared to confirm the fears of the Submarine Service’s worst critics. Nor could this be dismissed as an isolated incident. Four days later, Sturgeon, outward bound from Dundee encountered the returning Swordfish (Lt. Cecil Crouch). Gregory had not been warned of any returning submarines. Only a bow-cap failure on Sturgeon and the fast reactions of Crouch prevented a repetition of the Oxley tragedy.
The submarines had failed to interdict the break-out by German capital ships. The enemy warships had reached the Atlantic and Churchill was furious. At a time when the U-boats were pressing home their attacks with ruthless efficiency, the activities of British submarines appeared to be characterized by muddle and inefficiency . The only bright spot in an otherwise dismal picture came on 20th September when the RAF announced it was ready to take over patrols on the Ybrestod Line. Meanwhile there was bad news for the Sixth Flotilla. The engine frames of all the U-class boats were cracked. They would be out of action for at least a month. The burden of North Sea patrols would fall upon three ancient training boats .