On its first war patrol, the German Type VIIC U-boat U-570 had been on its way to join the U-boat packs operating in the area of the Northern Approaches. Having sailed from Trondheim four days previously under the command of Kapitänleutnant Hans-Joachim Rahmlow, U-570 had been directed, unsuccessfully, to intercept eastbound convoy HX 145.
During the early hours of Wednesday, 27 August 1941, having given up on the hunt for ships of HX 145, Rahmlow took his boat down because the heavy seas were upsetting his inexperienced crew. Two hours later, the order to resurface was given. U-570 did just that, but at what would prove to be a most inopportune moment. As the U-boat broke the surface little could Rahmlow have realised that, of the whole North Atlantic, he had chosen to do so directly underneath a pair of patrolling Lockheed Hudsons of 269 Squadron.
The appearance of the submarine brought an immediate response from the Hudsons. Unfortunately for the pilot of one, Sergeant Mitchell, his depth-charges failed to release. Having also dropped smoke floats which proved ineffective in the rain squall, Mitchell returned to carry out a square search. Again locating U-570, he homed in the second aircraft, this time piloted by Squadron Leader James H. Thompson. Thompson subsequently gave the following broadcast on the BBC:
“We knew early in the morning that there was a U-boat somewhere round that part of the Atlantic. Another Hudson out on patrol from my squadron had seen her twice, but both times she dived and got away. The Atlantic didn’t look very inviting when we left that morning. The sea was rough, and covered with angry white-caps. The clouds were low, and we kept on running into rain-storms and patches of dirty weather. We flew a good many miles close down to the sea – nothing to look at but clouds, and waves, and rain, and it was getting a bit monotonous.
“The first thing I knew about the U-boat was a shout from my second pilot: ‘There’s one just in front of you.’ He pointed out to the port bow, and there was a U-boat, roughly 1,200 yards away, just starting to crash-dive – they had seen us too. The second pilot was standing with his face pressed to the windscreen, and he had a better view than I had, so I called out to him: ‘Let me know when it’s time to attack, Jack.’ He nodded, and a few seconds later my whole crew shouted, ‘Now!’
“When I came round again in a tight turn, the whole area of the sea was churned up into a foaming mass, and in the middle of it the U-boat suddenly popped to the surface again. So we dived straight on to her and opened up with all the guns we had. I had my front guns going, the wireless operator dropped on his tummy and wound down the belly gun in the floor of the aircraft, and the gunner in the turret was firing practically the whole time. We had tracer ammunition loaded, and the red streaks of the tracer were flashing all round the conning-tower, and showering up the water all round the hull of the U-boat.
The first thing I knew about the U-boat was a shout from my second pilot: ‘There’s one just in front of you.’
“To our surprise, just as we dived in again to the attack, the conning-tower hatch was flung open, and about a dozen men tumbled out, and slid down on to the deck. We thought at first they were making for their guns, so we kept our own guns going hard. The Germans who had already got out of the conning-tower didn’t like that a bit, and they tried to scramble back again. The rest of the crew were still trying to get out of the hatch, and they sort of met in the middle and argued it out. It was a regular shambles for a few minutes. We could see them very clearly, for we were close on top of them, and they were wearing bright yellow life-saving jackets, rather like our Mae Wests.
“While the Germans were all stooging about in the conning-tower we continued to attack them, circling round each time and coming in again. That made the confusion below even worse. We went round four times, and we were just getting ready to dive on them for the fifth time when they decided they had had enough of it. They stuck a white rag of some sort out of the conning-tower, and waved it violently. We found out afterwards that it was a shirt they were using for a white flag.
“We all stopped firing, but continued to circle them with all our guns trained. The Germans were determined to make us understand that they had surrendered. They got hold of some sort of white board, and waved that at us too. We were still suspicious, so I dived right over the U-boat at about fifty feet, and then flew alongside her, to see what it was all about. They followed us all round with their white flag. We followed them all round with our guns trained on them. Practically the whole crew seemed to be in the conning-tower now, packed in so tightly they could hardly move. We were close enough to see their faces, and a glummer-looking lot I never saw in my life. Not a smile among them!
“It was only then that we began to realise that we really had captured a submarine, and they really had surrendered.”
“The difficulty then was how to get them in. I even suggested jokingly that I should drop my second pilot by parachute as prize crew, but he didn’t fancy it. But we were determined to get them ashore if we could, submarine and all, so we sent off signals to our base, asking for surface craft to be sent to pick them up. We soon knew that several were on their way, steaming as hard as they could go, and other aircraft were being diverted to relieve us.
“All we had to do was to keep circling the U-boat with our guns trained, to prevent the crew going below; we had to intimidate the crew, and keep them in the conning-tower. We kept that up for three and a half hours, and it was a bit trying. I dared not take my eyes off them for a single second – and when we finished circling at last, I couldn’t turn my head at all, my neck was so stiff. The wireless operator had even a worse job. He spent his three-and-a-half hours signalling furiously.”
we really had captured a submarine, and they really had surrendered.
“At last a relief aircraft turned up, a Coastal Command Catalina flying boat. We saw it coming, and we were scared it was going to attack the U-boat, so we flew towards it signalling hard that she had surrendered, and we were trying to take her prisoner. I think the actual signal we flashed was: ‘Look after our sub., it has shown the white flag’
“The Catalina boys understood, and they started to circle her too. Then another Hudson came up, and plenty more aircraft as the day wore on, but our petrol was getting a bit short, so we had to turn for home, and that was the last we saw of our U-boat. Of course the job wasn’t anything like finished. We had had the incredible good luck to find the U-boat, but the Catalinas kept up the watch for hours, much longer than we did, through gales and darkness. They stuck on to the U-boat magnificently. Then the Navy came along, and they put up a grand show too, taking the U-boat in tow in the most difficult conditions, and bringing her right in to shore, with all the crew prisoners.”
Thompson’s Hudson had been relieved by a Consolidated Catalina of 209 Squadron – AH553 – flown by Flying Officer E.A. Jewiss. The Catalina remained on station until, at 22.50 hours on the 27th, the armed trawler HMS Northern Chief arrived. Whilst Northern Chief had been racing towards him, Rahmlow was informed by signals that if he attempted to scuttle the U-boat, then an order would be issued to open fire sending U-570 and her crew to the bottom. The threats worked, for the crew of U-570 promptly signalled their agreement.
Taken in tow, the U-570 went on to become HMS Graph in Royal Navy service. Despite the best efforts of the U-boat’s crew, a wealth of vital information was gathered from the captured submarine. When the empty wooden box for U-570’s Enigma cipher machine was found – though the actual machine itself had been dumped overboard – it was discovered that a new slot had been fashioned to accommodate a hitherto unknown fourth rotor.
Thompson, along with his navigator and Second Pilot, Flying Officer William Coleman, was awarded the Distinguished Flying Cross for his actions.
This article first appeared inside the January 2014 issue of Britain at War Magazine as part of the ‘RAF on the Air’ series looking at a series of wartime radio interviews with RAF personnel. To purchase your own digital copy of this, and more of our back issues, please visit our page at Pocketmags: https://pocketmags.com/britain-at-war-magazine/issues