D-class Submarines of the Royal Navy

At the dawn of the 20th century, the submarine was firmly establishing itself within the world’s navies and the Royal Navy began to seriously look at its future applications. In 1905, a committee was set up to finalise the specifications for the next class of British submarine which would be significantly larger than the C-class boats which were then just entering service. While the C-class and the classes before it were short ranged vessels primarily operated in the coastal and harbour protection role, the new class would be the first British submarines designed for a more offensive role requiring greater endurance to conduct patrols at sea.

royal navy c class submarine world war 1 one

C-class submarine

The resulting D-class submarine was one of the most influential designs in the history of the submarine service incorporating numerous innovations that would be carried on in later classes. It was obvious from the very start that the new class of submarine was going to be significantly bigger than the types then being fielded in order to carry sufficient fuel and provisions for its longer ranged mission. They would also have to take greater consideration in to crew comfort and accommodation than previous classes. This saw the new design eventually swell to over twice the displacement of the C-class coming in at 483 tons on the surface and 595 submerged.

The shape of the new sub would also be came radically different compared to the C-class with the fitting of ballast tanks mounted externally along the pressure hull, a feature that would continue until the Oberon-class launched in 1960. These had the advantage of offering a significant increase in reserve buoyancy that made the submarine easier to manoeuvre and safer to operate in unsettled waters. It also freed up considerably more space inside the pressure hull for fuel and supplies. Another feature included in the design aimed at increasing stability was the fitting of hydroplanes on the forward half of the hull as well as the rear. These had been introduced on the C-class but unlike the earlier type they were positioned so that they remained submerged even when the submarine was cruising on the surface while the aft hydroplane was much further forward due to the unusual shape of the external ballast tanks. The angle of rise and dive angles were set at 50 degrees with the forward hydroplane and 70 degrees in the rear.

Perhaps the biggest departure for British submarine design that the D-class undertook was the adoption of a diesel-fuelled engine for cruising on the surface. This offered numerous advantages over the previous petrol-powered types including importantly for its envisioned mission, greater economy. It was also considerably safer since it was found that explosive fumes often built up in the pumps when using petrol engines. The French Navy had launched the world’s first diesel-powered submarine, the Aigrette, the same year the D-class committee met, proving the concept worked although there were some misgivings especially concerning reliability. The two diesel engines were 600hp units developed by Vickers and each drove their own propellers making the D-class the first British twin-screw submarine type. For propulsion underwater the diesels were cut off and power was provided by a 410kw electric motor.

The D-class had a comparatively impressive range of around 2,500 nautical miles making it a truly ocean-going warship while it could cruise at an economical 5 knots submerged for 45 nautical miles. The committee had demanded that the submarines be capable of around 13 knots on the surface and while it was reported that some of the class could on occasion exceed this figure they generally didn’t travel faster than 11 knots. They were designed for a top speed of 10 knots submerged but the actual speed was closer to 9 although it was rare for them to operate at such speeds due to the significant drain on the batteries this would incur.

Primary armament consisted of two forward 18-inch torpedoes mounted in tubes located vertically on top of one another and with a single reload available for each. The tubes were covered by a one-piece external cap designed to be rotated through 90 degrees to reveal them when it came time to fire. The size of the D-class led some on the design committee to raise concerns that it would not be manoeuvrable enough to escape attack by an enemy vessel and so provision was made for an aft torpedo tube that could be used to launch a torpedo at a pursuing attacker. Unlike the earlier coastal types which could signal the shore with lamps or semaphore, the sea-going nature of the D-class made wireless a requirement from the start and as such it was the first British submarine to be designed with the capability. The aerial was mounted in the coning tower and was extended when riding on the surface but unfortunately was quite short ranged.

D-class submarine Royal Navy World War One WWI

So many innovations were being incorporated in to this new design that the committee demanded that the construction of the first-of-class be undertaken by Vickers at Barrow-in-Furness under a veil of total secrecy. The building where HMS D1 was laid down on May 14th 1907 was therefore heavily guarded and all workers sworn to secrecy. The naval race with the Kaiser’s Germany was now in full swing and Germany was building their own submarines starting with the SM U-1 based on the Karp-class designed by Spaniard Raimondo Lorenzo d’Equevilley Montjustin for the Imperial Russian Navy. While inferior to the D-class, the U-1 was an impressive start for the Germans when it was compared to the previous British classes. Further east, the Russians began construction of the Akula as HMS D1 neared completion in 1907 but both these designs were still inferior to the British sub.

D-class submarine royal navy world war one 1 I (1)D1 was launched at Barrow-in-Furness on May 16th 1918, a year and two days after she was laid down, in a secret ceremony where the only invited guests were a handful of officers from the depot ship HMS Mercury. The submarine was formally commissioned in to the Royal Navy in September 1909 by which time work had started on HMS D2 and HMS D3 at Barrow. On May 3rd 1910, D1 received a new commander in Lieutenant Noel F. Laurence (later Admiral Laurence) who commanded the submarine through that year’s annual naval exercise. The exercise was the chance to get some invaluable experience of the new type engaged in operations similar to what it might experience in war. After loading supplies and fuel in Portsmouth, D1 slipped out of harbour and transited to its operating area off the west coast of Scotland completely undetected by the British Home Fleet. The submarine then conducted a three-day patrol simulating two attacks on British cruisers before putting back to port. Key to remaining undetected was D1’s battery capacity which allowed it to remain submerged during the bulk of daylight hours (in winter the D-class was found that it could remain submerged throughout the fewer daylight hours.)

This highly successful exercise was unfortunately marred by repeated troubles with the revolutionary diesel engines. The fact that D1 had two diesel engines meaning there was always a spare to fall back on was viewed as positively as possible by its supporters but it was clear Vickers had to address this problem if the D-class was to be a success. Despite grand ambitions for a fleet of 18 D-class vessels, the orders was scaled back to ten to allow Vickers time to remedy the reliability issues with the diesels so that these could be implemented on the recently laid down D4, D5, D6, D7 and D8. The latter two vessels in the class were constructed at Chatham Royal Dockyard in Kent and were followed by HMS D9 and D10.  During this time, the D-class would find itself receiving yet another first when D4 was completed with a 12-pounder quick firing deck gun and while this would not be fitted to any other members of the class, deck guns would remain on British designs until after World War II.

As experience on HMS D1 and D2 filtered back, a series of recommendations for improvements were submitted and began to be incorporated in HMS D9 and D10. These improvements became so extensive and included greater armament, increased displacement and improved engines that they became a new class entirely. As such D9 and D10 became the first of the new E-class submarines which would serve with great distinction during the Great War however they would also scupper plans for anymore D-class boats. HMS D6 would be the final D-class to be commissioned (April 19th 1912) while D8 was built to a marginally different configuration incorporating redesigned hydroplanes that were all set at 50 degrees for changing depth as opposed to the 50/70 split in the previous vessels. Along with the E-class fleet, the eight D-class boats formed the backbone of the Royal Navy’s patrol submarine force upon the outbreak of war in August 1914.

D-class submarine royal navy world war one 1 I (3)On August 28th 1914, the Royal Navy met the German Navy in their first major engagement of the war at the First Battle of the Heligoland Bight. The battle took place in the south-eastern North Sea after a British force attacked German patrols off the north-west German coast. Although entirely a surface action, British submarines did play their part and among them was HMS D2 and D8 who were tasked with patrolling the mouth to the River Ems in north-west Germany to block any German reinforcements that may attempt to enter the battle.

Nearly two months later, D8 was sent to shadow the German hospital ship Ophelia which was reportedly looking for survivors from German torpedo boats destroyed in an engagement with HMS Undaunted. The British had become suspicious of the hospital ship because of the amount of radio communication it was making with the German Admiralty and when her crew spotted the British submarine’s periscope they quickly changed course and headed for home even though they were protected under the articles of war which both sides respected in the early months. The M-class destroyer HMS Meteor was sent to inspect the ship under international law and observed her commanding officer throwing secret documents overboard as it approached. The British decided to seize the vessel as a war prize believing it had been spying on British warships thus invalidating its hospital ship status. The British renamed the ship SS Huntley and used it for transporting fuel from Portishead to Boulogne before it was sunk by UB-10 on December 21st 1915.

The class would suffer its first combat loss on November 3rd 1914. D5 was sailing near South Cross Buoy off Great Yarmouth in pursuit of German Admiral Franz von Hipper’s battlecruisers that had raided Yarmouth the day before when it struck a mine laid by the SMS Stralsund. There were only five survivors including Lieutenant Commander Godfrey Herbert who had been in command. Almost three weeks later on November 23rd 1914, D2’s commanding officer Lieutenant Commander Arthur Jameson was washed overboard while the submarine was charging its batteries on the surface. The submarine was then put under the command of Lieutenant Commander Clement Head but his captaincy would be shortlived for on November 25th, just two days after Jameson’s death, D2 was spotted by a German patrol boat on the surface off Borkum which proceeded to ram the British vessel. The submarine quickly sank taking Head and his entire crew of 25 with it.

Along with the E-class fleet, the D-class spent much of the early war years patrolling the Heligoland Bight as part of the British effort to contain the German Navy in port. On June 15th 1915, HMS D4 under the command of Lieutenant Commander John R. G. Moncreiffe stumbled across the unfortunate German netlayer Bielefeld that had ran aground and was being assisted by a German destroyer. Seizing the opportunity, Moncreiffe attacked the destroyer with a single torpedo which unfortunately missed and alerted the Germans to D4’s presence. The destroyer powered up and went in pursuit of the submarine in the extremely shallow water attempting to ram its coning tower that was only just below the surface. Luckily for Moncreiffe and his crew, he eventually managed to evade the destroyer and return to the position of the Bielefeld where they sank the German ship before escaping out to sea.

On August 13th 1917, D6 under the command of Commander William Richardson took part in an effort to lure out German U-boats using a decoy sailing vessel, HMS Prize so-named because she was actually a German topsail schooner captured in the English Channel mere hours after the war began. During the patrol, the two British vessels encountered the U-Boat UB-48 which exchanged gunfire with Prize before disappearing. Later that night close to midnight, D6 was on the surface when they observed Prize explode from a torpedo hit from UB-48 which had returned under the cover of darkness before escaping again. Prize sank with all hands.

D-class submarine royal navy world war one 1 I (3)

On September 12th 1917, D7 under the command of Lieutenant Oswald E. Hallifax was cruising off the coast of Northern Ireland when he and his men spotted the German U-boat U-45. U-45’s war up to that point had been a successful one having sunk 45,622 tons of allied shipping. Hallifax dispatched a torpedo at the U-boat which struck the rear of U-45 as its crew attempted to dive to safety. U-45 sank killing all but two of its crew who were rescued by D7 and taken prisoner.

HMS D3 2

The crew of HMS D3 

Tragedy was narrowly averted on February 10th 1918 when D7 was mistakenly depth charged by the M-class destroyer HMS Pelican. Now under the command of Lieutenant George Tweedy, D7 managed to surface and show her flag to the Pelican before any serious damage was done. Not as lucky however was D3 which on March 12th 1918, found itself the focus of attention from French airship AT-0 off Fecamp in the English Channel which mistook the identification rockets the British crew released for being German. The French airship dropped a series of bombs on the British submarine which sent it under the waves. Survivors of the attack managed to escape the doomed submarine and it was only when the French airmen heard them speaking English did they realise their mistake. Efforts to rescue the men proved to be in vain and they had drowned by the time help arrived.

D4 would add another U-boat to the D-class’ list of victims on May 12th 1918 when under the command of Lieutenant Claud Barry, it attacked and sank UB-72 in the English Channel south of Weymouth. The U-boat had been in service with the Germans for just eight months but accounted for sinking over 10,000 tons of allied shipping. Only three of the crew survived the sinking.

A month later on June 24th 1918, the D-class fleet would suffer its last wartime loss when D6 was attacked by UB-73 with a torpedo from a range of just 80 meters. UB-73’s torpedo passed under D6 and exploded throwing a column of water 30-40 feet into the air. At first it appeared D6 was unscathed but approximately half a minute later the front of the British submarine pitched down abruptly and it sank soon afterwards. Only two of D6’s crew survived the sinking and were taken prisoner by the Germans. When these men were questioned over the sinking after the war, the British Admiralty determined that the torpedo must have employed a magnetic pistol; a device used to trigger the warhead by detecting the magnetic field around a metal object such as a ship. UB-73 would survive the war to be surrendered to the French.

As 1918 drew on, the surviving four D-class vessels were becoming increasingly obsolete compared to the newer types then being fielded by the Royal Navy. When it was decided to conduct experiments in to new ways to detect a submerged submarine such as with piezoelectric hydrophones dipped in to the sea from airships (a precursor to modern ASW helicopters), the 10-year old D1 was chosen to be deliberately sunk off Dartmouth harbour. The submarine was sunk to a depth of 25 fathoms (150 feet) on October 23rd 1918 for the trials.

The remaining three submarines were briefly retained by the Royal Navy after the war but seldom went to sea or even had a permanent crew assigned. D4, D7 and D8 were then decommissioned in 1919 before being sold for scrap in December 1921 to H. Pounds based in Portsmouth. Despite their problematic birth, the D-class can be considered a success in their own right. However, their contribution to the development of British submarines and their operation cannot be overstated and would prove the genesis from which nearly every major British submarine class was derived until the nuclear age.

 

 

 

 

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World War I U-Boat wreck discovered off Scotland

The wreck of what is believed to be UB-65, a World War I German U-Boat lost in 1918, has been uncovered by divers laying an undersea power cable off the coast of Stranraer, Western Scotland.

Dr Innes McCartney, a historian and nautical archaeologist, told the BBC;

The submarine was caught on the surface at night, recharging its batteries. It saw the patrol ship coming. It attempted to do a crash dive to get away. Once the submarine was under water, it rapidly started flooding from above so they had no option but to blow all the compressed air they had, bring the submarine to the surface at which point all they could do was surrender.

The U-Boat then sank again for the last time.

The wreck was discovered by engineers involved in the £1bn Western Link project which involves laying a 239 mile sub-sea power line between Ayrshire and the Wirral that will carry renewable energy produced in Scotland to England and Wales. The engineers found the wreckage 120m north-west of the centre of the planned route. It is hoped further investigation of the wreck will confirm its identity.

Five Of The Most Significant Submarine Attacks In History

SM_U9_Postcard

The development of the submarine changed the very nature of naval warfare forever. Suddenly, the huge fleets of yesteryear found their supremacy threatened by an unseen force and for a long time they were largely defenceless to the new weapon. However, it took a certain type of courage to volunteer for submarine duties especially in the early days when their vessels were often as dangerous to their crews as to the enemy. As a result of this courage submarine commanders and their crews were often exceptionally daring in their efforts to fight the enemy.

Here are five of the most significant submarine attacks in history.


 

  1. The First Ever Submarine Attack in History

Submarine Turtle Eagle 1776Largely thought of as a 20th century invention, primitive submersibles have actually been around since the 17th century. On September 7th 1776 the submarine Turtle designed by American inventor David Bushnell was given over to the American patriot cause for use against the British in the American Revolution. Piloted by Ezra Lee, the submarine approached the British 64-gun warship HMS Eagle and attempted to plant a bomb on it. However, he was unable to secure it to his target’s hull and it fell off the British ship before detonating which saved the Eagle from destruction. Although a failure, Lee’s mission is considered the first submarine attack in history.


 

  1. The Cressy Catastrophe

HMS CresseyUpon the outbreak of World War I, Britain’s Royal Navy had the most powerful surface fleet in the world and the British people were confident that they were safe on their island nation as a result. That confidence was shattered on September 22nd 1914 when German U-Boat U-9 attacked a formation of three Cressy-class heavy cruisers – Aboukir, Cressy and Hogue.

When the first ship, the Aboukir, was hit the crews of the other two cruisers believed that the explosion was caused by an accident onboard and went to assist them. Seizing the opportunity, U-9 attacked the Hogue and sank it. The remaining British ship, Cressy, attacked U-9 before returning to rescuing survivors of the other two ships. U-9 attacked again and sank Cressy. In all 1,450 British sailors were killed in what was at that time an unprecedented victory for a submarine.

For more on this read The Cressy Catastrophe


 

  1. The Submarine That Sent A Nation On The Path To War

RMS LusitaniaOn May 7th 1915 the British liner Lusitania was travelling south of Ireland on a route from New York to Liverpool when it was spotted by the German U-Boat, U20, which was taking part in an attempt to blockade Britain’s sea lanes. At the time the US was neutral in the First World War but despite being warned by the Germans that they reserved the right to attack any ship heading for British ports a large number of Americans were aboard believing that the Germans would never target an ocean liner with 2,000 people on it.

They were wrong.

Shortly after 2pm, U20 fired on the ship and in the resulting explosion and sinking, 1,198 people were killed including 128 Americans. The attack outraged the American people who were at that time largely oblivious to the war in Europe and pushed America closer to the Allies before they eventually declared war on Germany in 1917.


 

  1. Submarine vs. Submarine

HMS VenturerContrary to the myth perpetuated by Hollywood movies, submarines sinking other submarines has only happened in exceptionally rare cases. In all but one of these incidents the target submarine was on the surface when it was attacked. The exception occurred on February 9th 1945 when the British submarine, HMS Venturer, detected the German U-Boat U-864 on the surface with engine trouble. The U-Boat was actually on a highly secretive mission to deliver two scientists and several key jet engine components to Japan, Germany’s ally, for use in their own jet fighter program.

Realising he had been spotted by a British submarine the captain of U-864 dived to escape. The captain of Venturer, 25-year old Lieutenant Jimmy Launders, attempted to match the U-Boat’s dive and by estimating the approximate position of the German vessel, fired a spread of six torpedoes in to its vicinity. One of the torpedoes successfully struck the U-Boat destroying it and its precious cargo. It remains the only time in history where one submarine has deliberately sunk another in combat while both were submerged.

For more on this read The Only Underwater Submarine-to-Submarine Kill in History


 

  1. The MV Wilhelm Gustloff

MV Wilhelm GustloffFrom the outbreak of World War II Germany’s navy, the Kriegsmarine, exercised a policy of unrestricted U-Boat warfare against the Allies. This in turn dictated a similar policy amongst the Allied navies and the oceans became a brutal killing ground as a result. In January 1945 this policy was about to reach its bloody climax and it would actually be the Germans who would be on the receiving end. The MV Wilhelm Gustloff was a cruise liner requisitioned by the Kriegsmarine for service as a hospital ship when the war broke out. When it became clear the vessel could no longer safely go to sea it was held in port at Gdynia in German-occupied Poland where it was painted in naval grey and used as an accommodation ship for trainee U-Boat crews.

By the start of 1945 the Soviet Red Army was pursuing the retreating German Army across Eastern Europe and so the ship was pressed back in to service to evacuate thousands of German troops, Gestapo officers, officials and civilians who had made a life in occupied Poland. On January 30th 1945, the ship along with another liner, the Hansa, and a torpedo boat made their breakout attempting to reach Germany through the Baltic. Official records show that over 6,000 people were onboard but the actual number was closer to 11,000 as a large number of civilians desperately crammed aboard and in the chaos of the boarding the crew simply gave up counting.

Shortly after leaving port the Hansa had to turn back because of mechanical problems but the Wilhelm Gustloff continued on before it was discovered by the Soviet Navy’s S-13 submarine. The S-13 torpedoed the overloaded vessel which quickly sank taking around 9,500 people with it of which nearly 5,000 were children.

It remains the biggest loss of life at sea in a single incident.

 

Lt Cmdr Basil “Byng” Boulding’s Logbook, December 1941 (No.812 NAS)

One of the best things about undertaking a project such as Defence of the Realm is hearing from the people who were actually there, their friends/comrades and their families. This week I was contacted by David Boulding whose father served with No.812 NAS of the Fleet Air Arm during the first half of the war. The squadron operated off the carrier HMS Ark Royal before the vessel was torpedoed by a U81 on November 13th 1941.

From then on the squadron operated from Gibraltar flying their Fairey Swordfish aircraft primarily on anti-submarine operations to protect the entrance to the Mediterranean. December 1941 was a particularly busy time for the squadron and David’s father was in the thick of it as his logbook shows which David has kindly contributed a picture of.

On December 22nd, a Swordfish from No.812 NAS attacked and sank a U-boat operating under the cover of darkness using radar to detect it. This signalled the turning of the tide in the war against the U-Boats (see Denying Dönitz the Dark ).

Normally, to save space I scale down the images I use on the site but in this instance I have uploaded the original image so this piece of history can be examined in detail.


 

This is a snap of my father, Lt Cmdr Basil “Byng” Boulding’s log book for 812 SQR operating out of North Front not long after the sinking of the Ark Royal (he told me he didn’t get his feet wet and flew off). That month he flew 72 hours 25 minutes. It must have been exhausting! Sadly his first log book went down with the Ark because he was active right from September 1939 in one of the first events of the war.

He made several attacks on submarines including one confirmed hit Dec 16th. You’ll see the note on the 20th December where he flew with Lt Philips and PO Reason.

No.812 NAS Fairey Swordfish HMS Ark Royal

I found a note about that period at North Front in an article about his TAG (P Reason) on the internet when he or his family were selling his medals (sad that). I have also a photo (above). My father is second left (the small one) and his TAG, Reason extreme right. This was when he was awarded his DSC. This photo is to be found on the Imperial War Museum website.

– David Boulding

I would like to thank David for sharing this piece of his family’s history.


 

If you have photographs or have a family story you wish to share on Defence of the Realm than you can email defencerealmyt@gmail.com. You will of course be given full credit for your contribution and can even promote your own website or social media account.

Submarine Patrol (1943)

U-boats are evil. Submarines are good.

That’s the general impression the Royal Navy wanted to give the public during the war. The fact that Germany’s submarines were called U-boats helped distinguish them in propaganda films such as this even when tactics and operations by both sides differed only little. Nevertheless this is a fascinating – if somewhat scripted – account of RN submarine operations during the war.

Enjoy.

NEWS: First World War U-Boat wreck identified

Despite having been discovered by divers working on behalf of Scottish Power Renewables and its partner Vattenfall in 2012 researchers have only now been able to positively identify a  German World War I U-Boat laying 56 miles off the coast of East Anglia. The wreck is of the Imperial German Navy’s U-31 which set sail for a war patrol from Wilhelmshaven in January 1915 – almost 100 years ago exactly. Contact with the 31 officers and men was lost soon after and it is now believed that the vessel was sunk by a British defensive mine.

Mark Dunkley, marine archaeologist at Historic England, told Sky News;

After being on the seabed for over a century, the submarine appears to be in a remarkable condition with the conning tower present and the bows partially buried. Relatives and descendants of those lost in the U-31 may now take some comfort in knowing the final resting place of the crew and the discovery serves as a poignant reminder of all those lost at sea, on land and in the air during the First World War.

Tough to Sink

S.S. Laurentic before her conversion to armed merchant cruiser in 1939 (u-boat.net)

S.S. Laurentic before her conversion to armed merchant cruiser in 1939 (u-boat.net)

It has long been the practice in wartime for the British government to requisition civilian vessels for war service. Often these vessels are used in the logistics role supporting the Royal Navy at sea or the British Army and Royal Air Force in foreign lands. The practice has been used as late as the 1982 Falklands War where perhaps most famously the ocean liner Queen Elizabeth II was used to ferry over 3000 troops to the South Atlantic. Using civilian ships in wartime is a precarious business at best. They are seldom designed with the same level of protection a warship is afforded making them very vulnerable and their vital role in supporting the war effort makes them highly prized targets for the enemy.

One such civilian ship taken over for use by the Royal Navy was the Cunard White Star Line passenger ship the Laurentic. Requisitioned by the Admiralty a week before Germany invaded Poland on September 1st 1939 the vessel was put in to dock for conversion to an armed merchant cruiser which was completed in a remarkably short space of time. HMS Laurentic F51 was accepted in to service on October 15th 1939. As part of her conversion she was armed with seven Breech Loading 5.5inch (140mm) Mk I guns and three QF 4inch (102mm) Mk.XVI naval guns. She was also fitted with a quantity of depth charges for use against submarines.

The vessel was, like many of her kind, primarily employed on patrol and escort duties; armed merchant cruisers were effectively the last line of defence with the Royal Navy’s main fleet and aircraft being the first. Her start to the war was relatively uneventful but all that changed on the evening of November 3rd 1940. A little after 2140 hours her commanding officer, Capt E.P. Vivian RN, was informed that the radio room had received a distress call from an unescorted merchantman, the Casanare, stating it had been attacked by a U-Boat. Along with another armed merchant cruiser, HMS Patroclus, Laurentic raced to the scene west of Ireland at a place called Bloody Foreland.

A sister-ship to Casanare (wrecksite.eu)

A sister-ship to Casanare (wrecksite.eu)

Unknown to Captain Vivian and his men they were about to face off against one of Germany’s greatest U-Boat aces, the brash and skilled Kapitänleutnant Otto Kretschmer (known as “Silent Otto”) and his crew of U-99. Kretschmer’s attack had been a textbook example of U-Boat warfare, catching the Casanare completely by surprise. The torpedo struck just aft of the vessel’s bridge and she began to list heavily enough for the crew to begin abandoning ship. The wireless operator aboard U-99 suddenly found his headset alive with messages between their victim and the two approaching ships all of which were transmitted uncoded and in plain language.

Kretschmer continued to shadow the sinking Casanare while surfaced and it was not long before he detected the two ships coming to its aid. Picking his moment carefully, Kretschmer waited for the Laurentic to come in to his sights and at 2250hrs he unleashed his deadly arsenal on his second unsuspecting victim of the night (this early in the war few ships had radar to detect a surfaced U-Boat at night but by 1945 this kind of operation would have been suicide for a U-Boat commander). Launched from a distance of one and a half kilometres and incredibly while the U-Boat was turning the torpedo struck the Laurentic amidship near the boiler room tearing open a gaping hole in her side. Kretschmer watched the ship expecting it to sink and indeed a number of her crew had leapt overboard in the chaos of the blast but as the smoke dissipated the Laurentic proved that she was not done for yet and remained stubbornly afloat.

Kretschmer made two more attacks on the Laurentic, one at 2320hrs and another at 2330hrs with the range now having decreased to just 250m. The crew of the Laurentic briefly spotted the U-Boat on the surface and began shelling the submarine which quickly slipped away. The Laurentic was now heavily damaged and was riding much lower in the water than it should be convincing Kretschmer that the ship was finally done for and so he turned his U-Boat away to assess his situation.

hms patroclus

HMS Patroclus (u-boat.net)

In the meantime, HMS Patroclus had arrived on station and began efforts to rescue the crew of the Laurentic many of whom were abandoning the ship. The Patroclus’ Captain, William Wynter, ordered that two depth charges be launched over the side in an effort to frighten the U-boat away. He couldn’t have known that Kretschmer was still on the surface unseen in the night. Believing he had successfully drove off the U-Boat, Wynter’s crew began to rescue their comrades but Kretschmer had come about and at 0022hrs the Patroclus was hit by a torpedo from U-99 killing an unknown number of men aboard a lifeboat from the Laurentic that was being hauled aboard at the time. Like the Laurentic the Patroclus refused to sink and twenty minutes later at 0044hrs a second torpedo was launched in to the ship. The torpedo malfunctioned and missed its aim point hitting below the foremast. No doubt gritting his teeth Kretschmer fired a third torpedo at 0118 hrs but as he did so the British lookouts spotted the U-Boat and Kretschmer found his vessel taking fire forcing him to flee yet again.

Dumbfounded by his enemy’s refusal to sink, Kretschmer searched for his first target, the Casanare, to confirm it had indeed sunk. Two lifeboats bobbing in the water at her last known position offered the proof he was looking for when suddenly the air around him growled with the sound of aeroengines as an RAF Shorts Sunderland flying boat appeared over the scene. Kretschmer ordered his U-Boat to dive and the RAF aircraft was unable to launch its weapons but remained on station trying to locate the submarine.

Kretschmer used his time submerged wisely and reloaded the torpedo tubes. With the sound of the Sunderland’s engines dissipating he felt confident enough to surface at 0330 hours. Rather arrogantly he went back to the site of his attack on the two armed merchant cruisers and saw that Laurentic and Patroclus had still yet to sink! At 0435hrs he fired a fourth torpedo at Laurentic which struck astern. The blast ignited the depth charges stored in that area resulting in a huge explosion. The Laurentic’s luck ran out and the ship began to sink by the stern disappearing forever.

Kretschmer then turned on the Patroclus but as he did so his own lookouts spotted a destroyer, HMS Hesperus, approaching on the horizon. Rather than be satisfied with sinking the Casanare and the Laurentic he made a hasty attack on the Patroclus. At 0516hrs a fifth torpedo struck the ship fired from U-99 but the British ship refused to go down one last time prompting Kretschmer to fire a sixth torpedo. That was the end of the Patroclus and the hull crumbled into pieces before finally sinking. 114 sailors had been killed in the whole incident.

Kretschmer and the crew of U-99 celebrate in late 1940 (commons.wikimedia)

Kretschmer and the crew of U-99 celebrate in late 1940 (commons.wikimedia)

Kretschmer immediately ordered his U-Boat to dive as the destroyer zeroed in on him. Kretschmer and his men now paid for their victory as they were repeatedly depth charged by the Hesperus but the destroyer failed to score a direct hit and Kretschmer returned to Germany a hero.

So just what was the secret behind the Laurentic and the Patroclus that kept them afloat for so long? Was it excellent damage control techniques? Perhaps it was superb craftsmanship in the construction of the two vessels? Actually it was neither. It was in fact the placing of thousands of empty oil drums inside the hull of the ship. This dramatically increased the overall buoyancy of the vessels which meant that despite several gaping holes in the hull the barrels kept the vessels afloat making them very tough to sink.