A U-Boat in the Royal Navy (Part 3)

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HMS Graph

Part 3 – HMS Graph is born.

Few vessels were ever tested as thoroughly as the captured U-570. Efforts were made to make her fully submersible again so as to fully evaluate the performance of the Type VII U-Boat. At the same time moulds were taken of the hull to test different shaped explosive charges for new depth charge designs. Just when the repair work was ready to go ahead Winston Churchill stepped in and began an effort to convince the Admiralty to hand the vessel over to the Americans. Churchill’s motives for this was that firstly the neutral Americans had the infrastructure to complete the repairs while Britain could barely spare a bolt it was so geared for war. He also believed that by handing over the vessel he would be further drawing the US into the Battle of the Atlantic and perhaps even the war itself.

The Admiralty successfully resisted his efforts although they did allow almost unrestricted access to the US Navy intelligence officers who arrived to inspect the vessel. Churchill’s interest in the vessel was not lost however and he then proposed that the vessel be given to the Yugoslavians to operate in the Mediterranean. This second plan died a quick death for many reasons, some technical and some political, but above all the lack of a skilled Yugoslavian crew who could man it meant the idea had to be dropped. Finally, Churchill conceded to the Admiralty’s desire to repair and test the vessel itself with the ultimate intention of putting the vessel in to frontline service against the Germans.

With that in mind a new name was needed as “HMS U-570” was not going to be looked upon favourably by anyone. To help identify her she received the pennant number “P715” which was painted on the sail but a name beginning with “G” to signify she was of German origin was needed. Just how the name HMS Graph was selected is disputed with some believing it is a play on the German word Graf meaning Count. Given its spelling however the real explanation is probably that it reflected the extent of the testing carried out that used literally miles of graph paper. Either way, HMS Graph was born.

HMS Graph interior

RN officer at U-570/HMS Graph’s chart table

Trials were conducted under the command of Lieutenant Commander E.D. Norman and between September 1941 and June 1942 every aspect of the vessel’s performance was examined. The trials proved just how good German submarine design really was compared to the Allies. It seemed that the Germans had a better understanding of keeping a submarine undetected than the Americans or British did with features such as rubber padded floors in the machine room that suppressed the vibration of the electric motors when operating submerged. This made detecting the vessel by hydrophone very difficult and impressed the Allies so much that they immediately copied the system in their own vessels. One of the most secretive projects that involved the Graph was the copying of the control room’s layout. This was then used to train specialist boarding parties who would (in theory) be able to fight their way in and capture more U-Boats.

By Mid-1942 the Admiralty was satisfied that it had learned all it could from the U-Boat and therefore felt willing to put it in the frontline. HMS Graph was placed under the command of Lieutenant Peter Marriott who had served under Norman during the trial phase and had thus became well acquainted with the vessel. On October 8th 1942, the former German U-Boat set sail under the Royal Navy ensign to wage its war against its former master.

HMS Graph transited south to patrol the west coast of France to attack any U-Boats or German surface raiders attempting to break out in to the Atlantic to intercept the convoys between Britain and North America. Just like their German counterparts, British submarine crews had to contend with harassment from the air which for the British meant keeping a watchful eye for the German Focke-Wulf Fw200 Condor. This large four engined aircraft had built an enviable reputation for successfully tracking convoys and directing U-Boats to their position. It was also able to attack submarines with bombs and depth charges.

The Fw200 Condor provided the U-Boats with vital intelligence

The Fw200 Condor provided the U-Boats with vital intelligence

On the afternoon of 21 October 1942 HMS Graph was operating 60 miles off Cape Ortegal when her lookouts atop the sail spotted the menacing shape of a four engined maritime patrol aircraft. The vessel immediately went to diving stations with the lookouts rushing down below frantically closing the hatches behind them. Soon the vessel was slipping beneath the protection of the waves but as it did the hydrophone operator detected a contact in the local vicinity. Weighing up all the information he had such as the location of where Allied submarines would be operating Marriott assumed, quite correctly, they had detected a U-Boat.

Marriott set about stalking his prey. After nearly a quarter of an hour of following the contact which was travelling on the surface he raised his periscope and spied the distinctive tail of U-333. Marriott plotted a firing solution and when he was satisfied he gave the order to fire a spread of four torpedoes. Several tense minutes passed. Then the hydrophone operator reported loud explosions as the torpedoes detonated followed by what appeared to be the sound of bulkheads failing. The crew of the Graph cheered as they celebrated their victory and a few days later returned to port to claim their kill which for Marriott meant receiving the Distinguished Service Order for his courage and skill.



Alas, history would steal the claim away from the Graph. Records obtained post war showed that U-333’s own lookouts spotted the torpedo tracks early enough for her to take evasive action. The U-Boat’s captain, Peter-Erich Cremer, later said that after the torpedoes passed by then detonated harmlessly in the distance. As for the sounds heard afterwards that the Graph mistook for collapsing bulkheads he believes that damage already inflicted on the U-Boat by a British escort ship that had rammed the U-333 on the surface could account for this. At the time it was detected by HMS Graph, U-333 was limping back to its base following the collision.

Unaware of this fact however, HMS Graph departed Holy Loch again on the 19th November 1942 hoping to repeat the “success” of the previous patrol. Marriott and his men thought the opportunity was presenting itself when they received a signal that an Italian transport ship, the Cortellazzo, had entered the area and it was to be sunk with the highest priority. Unknown to Marriott, British intelligence had discovered that the Cortellazzo was carrying over 2,000 tons of advanced machinery destined for Japan to help them improve their own equipment to use against the Allies in the Pacific. Later in the war these journeys were actually undertaken by U-Boats as surface vessels became increasingly vulnerable. Equipment given to the Japanese by the Germans this way included jet and radar technology the latter of which was fitted to the battleship Yamato. Marriott set up a search pattern but his efforts were to prove fruitless as the Cortellazzo slipped by undetected by the Graph only to be intercepted by HMS Redoubt, a destroyer-escort which sank the vessel after ordering her crew off and then rescuing them. The frustrated crew of HMS Graph returned to port on the 8th December 1942.

Any hope of a Christmas at home were dashed however when the crew were ordered to set sail again on Christmas Eve 1942 for a third patrol. This time they were operating with a British wolfpack of four submarines heading north for the Norwegian coast to intercept German warships and submarines attempting to interfere with convoys to Russia as well as North America. Upon arriving on station the wolfpack received word that the German heavy cruiser Admiral Hipper was expected to make a break for its port in Norway.

Admiral Hipper

Admiral Hipper

 The Admiral Hipper was one of the German Kriegsmarine’s main surface combatants and a very real threat to the convoys. However, on the 31st December the Admiral Hipper along with another cruiser and six destroyers attacked the convoy JW 51B heading north for Russia. In what became known as the Battle of the Barents Sea the German force faced disaster in the face of a potent British escort force who used superior tactics to circumvent the German’s superior firepower. The Germans lost one cruiser and one destroyer with the remaining force, including Admiral Hipper, being made to scatter and retreat. Unknown to British intelligence or the crew of the Graph Hitler had been so infuriated by the disaster that it effectively meant the end of any real attempt to attack convoys by surface vessels and priority was soon given to the U-Boats. Nevertheless, at 1am on the 1st January 1943 Marriott spied the menacing silhouette of the Admiral Hipper and prepared his attack. Frustration would once again curse the Graph as Marriott realized the Admiral Hipper was too far off and travelling too fast for any chance of a successful attack.

Unable to pursue, the Graph lost contact but as though fortune was smiling on them they suddenly ran in to two of the German destroyers that had taken part in the attack. While Admiral Hipper was relying on her great speed for protection the two destroyers were relying on their manoeuvrability and were zig-zagging; a common tactic to make a ship difficult to attack with a torpedo. At 4:23am, Marriott ordered the Graph to close within 7,000 yards of the two ships and prepared a spread of four torpedoes in a wide pattern in order to counter the defensive pattern the destroyers were taking. The torpedoes fired and after a few moments a loud explosion was heard through the hydrophones indicating a hit. The Graph then retreated from the area fearing depth charge attack from whichever destroyer hadn’t been hit. History would prove cruel twice to the crew of the Graph as again post war records proved that all four torpedoes missed their targets and the explosion must have been caused by a torpedo hitting rocks or malfunctioning.

HMS Graph returned to port on the 13th January. Her engineering log showed that she was beginning to look in poor shape as a number of breakdowns from a lack of spare parts was beginning to blight the vessel. It was therefore decided to take her off the frontlines to spend her last days as a target for air and surface battery crews to train their weapons on. Shortly after decommissioning in February 1944 she was taken undertow for scrapping on the River Clyde but during gale force winds her tow rope snapped and she was blown aground near Coul Point, Scotland. She was never recovered and broken up for scrap in situ over the following 20 years but some of it remains even today.

The legacy of U-570/HMS Graph lays in revealing to the Allies how much more sophisticated the German submarines were and how they could improve their detection methods. This went a long way to helping the Allies finally defeat the Germans in the Battle of the Atlantic.


4 responses to “A U-Boat in the Royal Navy (Part 3)

  1. Pingback: A U-Boat in the Royal Navy (Part 2) | Defence of the Realm

  2. Pingback: A U-Boat in the Royal Navy (Part 1) | Defence of the Realm

  3. Pingback: Defence of the Realm – Royal Navy | Defence of the Realm

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