A U-Boat in the Royal Navy (Part 1)

A U-Boat in the Royal Navy (Part 2) >
A U-Boat in the Royal Navy (Part 3) >
HMS Graph

Part 1 – The RAF’s Prize

It has long been a tradition among the world’s major navies to capture enemy vessels and then impress them in to service against their former masters. It is a tactic as old as naval warfare itself and it allows a navy to replenish its losses quickly and remove a threat all at the same time. In the 20th century naval weapons had evolved to such a point where their destructive power was such that it was very unlikely that an enemy ship could be captured in such a good condition that it could be used again. However there were some isolated incidents that resulted in the taking of enemy ships as war prizes.


One such incident was the case of U-570, a Type-VIIC U-Boat launched on the 20th March 1941. Having failed to crush the Royal Air Force in the Battle of Britain, Hitler knew that Britain had to be starved in to submission and the way to do that was to flood the Atlantic with U-Boats to intercept the supplies from the United States that were effectively keeping the country in the fight. The Germans were certainly capable of turning out some impressive U-Boats that were either the equal or superior of their allied equivalents. Unfortunately for Hitler a tool is only as good as the person using it and in 1941 there was a severe shortage of experienced crews to man the increasing numbers of U-Boats. U-570 was a prime example of this. Of her 48 crew only 4 of them had actually undertaken a combat patrol in a U-Boat before joining U-570. Her commanding officer, Hans Jochiam-Rahmlow, was not one of them having only ever undertaken a single training patrol onboard U-58 and then another training patrol during the work up to U-570 becoming operational. His previous experience was not even on a surface ship but on a defensive shore battery. 38 of the crew were new to the German Navy and had almost no previous experience. This was the situation that Jochiam-Rahmlow found himself in when he and his U-Boat left for their first patrol on August 24th 1941. Confidence was still quite high however as the technology and tactics the Royal Navy and Royal Air Force were using to destroy U-Boats was still maturing and successes were infrequent.


Things were slowly changing for RAF’s Coastal Command however. Having been known as the “Cinderella Service” because of its hand-me-down aircraft that weren’t always suited to its needs they were now getting far more capable types tailored for their requirements. One such aircraft was the American-built Lockheed Hudson; one of those great designs that has had little fanfare outside the annals of military aviation (see above picture). The Hudson gave Coastal Command an aircraft with respectable enough range to roam the northern approaches near Iceland to try and catch the U-Boats on their way in to the Atlantic where there was still a gap in air cover. In terms of spotting the U-Boat there was still a degree of luck involved. On the morning of August 27th 1941, a Hudson of No.269 Squadron flown by Sergeant (Aircrew) Mitchell was about to get very lucky and then very unlucky. His aircraft was patrolling south of Iceland when they spotted a U-Boat on the surface in the early hours of the morning; it was U-570. He swung his aircraft down to attack with bombs but the racks failed to eject them and U-570 escaped. Jochiam-Rahmlow elected to keep his U-Boat underwater for a few hours even after the Hudson had given up and returned to base. This was as much to do with offering the crew a break from the rolling of a U-Boat on the surface as it was to stay undetected; a large number of the inexperienced crew had become incapacitated by sea sickness.

Type VII

At 10:50am he decided it was time to resurface. The U-Boat broke through the water and Jochiam-Rahmlow climbed out of the hatch in to the North Atlantic air. A strange sound greeted him; a loud buzzing. Then to his horror he realized that he had surfaced his U-Boat directly beneath another No.269 Squadron Hudson. Terror-stricken, he tried to get below and dive again but this Hudson’s weapons were working perfectly. U-570 was only partially submerged when the Hudson dropped a stick of four depth charges around the submarine shaking it violently to the point where it almost rolled over and it had lost all electrical power. The air quickly became contaminated making it impossible for the crew to survive submerged and so the decision was taken to surface once again perhaps hoping that the Hudson had gone. It hadn’t. The Hudson saw U-570 surface and being out of bombs or depth charges the aircraft resorted to straffing it with its machine guns. Jochiam-Rahmlow wanted to have his men take their anti-aircraft positions but it was obvious that to do so would be suicide and fearing another depth charge attack (not knowing the Hudson had none left) he ordered his men to hold up a large white sheet. The crew of the Hudson couldn’t believe their eyes when they saw that their quarry were surrendering.


An RAF Catalina flying boat was scrambled to the scene so it could land near the U-Boat and accept the surrender. However while the Hudson waited for the Catalina, Jochiam-Rahmlow radioed his situation to German Naval Command who immediately sent out signals to other U-Boats in the area instructing them to go to U-570’s position and assist in their rescue. The German crew then began destroying their radio and coding equipment before it could fall in to British hands. U-570’s message was uncoded however and the British Admiralty intercepted it. A race was now on between the Royal Navy and the German Kriegsmarine to get to the scene first. The Hudson ran out of fuel and so the Catalina took over guarding the submarine until Allied ships arrived while her crew remained onboard. The Catalina was ordered that if no vessel turned up before sunset the aircraft was to signal the U-570 ’​s crew to abandon her after which the Catalina would destroy it. As it happened the first vessel to reach the U-boat was HMT Northern Chief which was guided to the scene by flares dropped by the Catalina. The Captain of Northern Chief was determined to make sure the Germans didn’t scuttle their ship warning he would fire on them if he saw any effort to sabotage the vessel.


The crew of U-570 repeatedly requested to be taken off the U-Boat but the request was refused partly because of space concerns aboard the armed trawler and partly because the Northern Chief’s captain believed they were less likely to scuttle the U-Boat if they remained onboard. The next day disaster nearly struck when an aircraft belonging to No.330 (Norwegian) Squadron spotted the U-Boat and the Northern Chief unaware of what was happening and attacked exchanging fire with the Northern Chief. Fortunately the attack was ineffective and there were no casualties. Additional vessels arrived on the scene including a Royal Canadian Navy destroyer and U-570 was taken under tow to Iceland arriving on the 29th August. The Kriegsmarine had lost the race to svae their comrade.

The RAF and the Royal Navy now had a fully intact German U-Boat.

A U-Boat in the Royal Navy (Part 2) >
A U-Boat in the Royal Navy (Part 3) >


7 responses to “A U-Boat in the Royal Navy (Part 1)

  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 3) | Defence of the Realm

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

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