"Hidden by London's elegant public buildings, just yards from Trafalgar Square, is a dark, forbidding block known as the 'Citadel'." "Sixty years ago this bunker was at the heart of the secret war against Hitler's U-boats." "In an airless sub-basement, twenty feet below the ground," "Naval intelligence sought to track the enemy in the Atlantic." "At first, with little success." "Britain depended on its lifeline to North America, but in the first eighteen months of war the Germans sank more than five million tons of shipping." "It was a battle for survival and Britain was losing it." "But in the spring of 1941 , a new source of intelligence began to flow into the 'Citadel' which promised to transform the battle of the Atlantic, and to shape victory from defeat." "On May 7th, 1941 , a British listening station intercepted a signal to a U-boat on war patrol in the Atlantic." "It was from U-boat Headquarters." "That much was clear." "But the message itself was in code." "Dozens of signals like this were intercepted every day." "If sense could be made of them," "Naval intelligence would be able to locate an enemy hidden in three million square miles of ocean." "The signal was sent to a U-boat hunting in the waters south of Greenland - the U-110." "The message was encoded on an Enigma machine." "The settings for this machine would change daily, and the tables containing the settings, were changed every month." "How safe was the code?" "We were told that the odds were at least one to a million." "You could say that it was as safe as winning the jackpot on the lottery." "The Enigma machine on its   own wasn't enough to break the code." "You also needed the code tables." "The message from headquarters promised immediate action." "The first for the U-110 in almost two weeks." "A convoy has been spotted and we were ordered by U-boat Headquarters to try and intercept it." "We were at last close enough to be able to do that." "The U-110's Commander," "Fritz-Julius Lemp, was an experienced hunter." "A holder of the Knights Cross, Germany's most prestigious decoration." "The convoy was sighted on the morning of May the 9th." "Lemp chose to risk a daylight attack." "Then we attacked." "Fired at two steamers." "I followed the torpedoes until they hit the targets." "Suddenly there was a terrific explosion, I think on the starboard bow   and we knew a ship had been torpedoed." "Then another ship was hit." "Turned the convoy the other way, raced over and started picking up the contacts." "I said my mate, 'Fritz, listen." "They've got us." "We're being echo-located.'" "The last depth   charges caused serious damage and we had water and diesel oil leaking into the U-boat." "The control room looked like a wrecked kitchen." "The lights went out and well, it really was the end." "The U-boat, like the one filmed here, shot to the surface taking the Royal Navy escort ships by surprise." "It is the dream, of course, when you attack to have a U-boat coming to the surface." "It happened so seldom." "As we opened fired the noise in that U-boat must have been absolutely terrific." "I can still hear Commander Lemp as he opened the hatch." "He shouted down, 'Uhlandstrasse, last stop, all change.'" "This was the last stop for us." "I climbed from the control room through the   tower up to the bridge." "The Commander was standing there." "I said, 'Sir, the secret things are still down there.'" "He just said, 'Leave it, Wilde, the boat's sinking anyway.'" "The British rescued those they could, but seventeen of the crew, including Commander Lamp, were lost." "The U-110 remained stubbornly afloat." "My captain turned to me and said," "'Look, you Sub, you take the boarding party and get what you can out of her.'" "One couldn't believe that they'd just left this U-boat." "I felt sure there must be somebody down below   and so going down that last ladder with my revolver holstered, I felt terribly vulnerable and very frightened." "Very eerie." "No noise at all, deathly silence." "Nobody there." "So I then shouted up to my boarding party who I'd left up on deck to come down." "And then we started collecting everything we could." "And the telegraphist came along to me and said," "'Look, there's something very interesting here, you'd better come and see.'" "So I went along and there was this typewriter thing." "We both pressed a few buttons and it lit up in rather a strange way and of course a mass of cipher books which didn't mean anything to us." "Four days later the intelligence haul was delivered to a Victorian mansion in the Buckinghamshire countryside." "This was Bletchley Park, the government code and cipher school, a place so secret it was known in official documents as 'Station X.'" "Staff Sergeant King." "Right sir, coming." "By 1941 , the Bletchley code breakers were able to read both German Army and Air Force signals." "Only the Navy's Enigma codes were unbroken." "The material from the U-110 helped to change all that." "We got out almost everything in spring/summer of 1941 ." "There may have been an occasional day that didn't come out or something, but no, thorough steady success." "The intelligence material captured in the spring offered the cryptographers enough of an insight into the mechanics of the codes for them to crack the daily wheel settings, even when in the summer the tables changed." "After June and July were over, when we had the messages on a plate, then we had to solve each day separately and it was an extremely satisfying job." "And each time you had to do some work and you knew what you" " what you were doing was useful." "Wonderful." "By the summer of 1941 , a flood of decrypted signals was clattering down the secure teleprinter lines from Bletchley to the Admiralty." "It was known as 'Ultra' or 'special intelligence.' with which the decrypts came into us, there were just piles and piles of them and we   were reading enemy traffic and knowing what they were doing," "probably at the same time as the recipient of the signal." "At the other end of the teleprinter line, was the Admiralty's intelligence centre, the 'Citadel.'" "At the heart of the secret bunker a small team of intelligence officers sought to track U-boats in the Atlantic." "The submarine Tracking Room was to mirror operations at U-boat Headquarters, and lest anyone forget, a grim portrait of Karl Donitz, the leader of the U-boat arm, hung on the wall." "In the summer of 1941 ," "Ultra was to transform the work of the Tracking Room" " and the battle in the Atlantic." "On June 21st, a British cruiser sank the German supply ship Babitonga, one of the network put in place to refuel surface raiders and U-boats at sea." "Within a month," "Naval intelligence was able to lead British warships to nine German tankers." "It was a severe blow to Donitz's plans for long distance operations in the Atlantic." "To make matters worse, his U-boats were also struggling to find convoys closer to home." "In May, 1941 , they'd sunk fifty-eight ships." "In July, just seventeen." "Donitz began to suspect an intelligence failure." "He'd send his signals and intelligence   officer to Berlin and this man was told," "'Find out if everything is okay." "Can we trust this?" "'" "And again and again he would return with reassuring words," "'Nothing can have happened, it's got to be okay.' But one always felt   that Donitz had, I'd say, a premonition, that something wasn't quite right you know?" "On the day the British captured the Enigma materials from the U-110," "Admiral Donitz was appearing in a film being given its gala premiere in Berlin." "The leading parts, with the exception of Donitz, were played by actors." "But the U-boat was real enough." "The U-123 had already sunk eighteen ships." "That summer the U-123 was to set out on war patrol under a new commander." "It wasn't that simple   taking over a successful boat." "I had to impose myself, of course." "The older crew members in particular were a bit   reluctant to accept me because our first voyage was a journey south to the Equator." "They'd never done a long voyage, so it wasn't easy getting them behind me." "Hardegan was determined to make his mark." "His maiden voyage in 123 was to take him south along the African coast, where hunting was supposed to be good." "At first it was." "By the end of June, 1941 , he was able to report his first successes to Donitz." "At Battle Stations." "Turned onto a parallel course." "A hit at the bridge and a bright fiery glow." "There's an oil patch at the sight of the sinkings and a few people are floating in the water holding spars." "But U-123's war patrol was being tracked by the British." "Hardegen's signals were read in the Citadel, just hours after he's sent them." "Time enough for convoys to be directed away from U-123." "The Tracking Room was carrying out the same operation with a dozen more U-boats right across the North Atlantic." "On June 24th, Donitz sent a message to his commanders, urging them to press home the attack more vigorously." "For Naval intelligence, this was confirmation that the U-boats were experiencing a lean time." "Donitz was tetchy." "Finding targets, how should I put it?" "This was getting harder and harder." "The U-boats locations were known and the convoys were being directed around them." "U-123's war patrol began to fizzle out." "At least for the U-boats in these waters there was time to relax in the African sunshine." "I organised a deck party with sausage snatching, shark fishing and the crew was able to swim." "The water was around 30 degrees, it was lovely." "We could have a nice shower." "We took our clothes off." "Everyone was naked, you know." "By July the 14th, U-123 had reached Freetown, on the coast of Sierra Leone." "This was an assembly point for convoys preparing to make the journey home to Britain." "There were hopes, at last, of an easy success." "They were short lived." "The Royal Navy had been tipped off by U-123's own signals." "And now the only ships passing in and out of Freetown were the ones they couldn't sink." "We had them in our sights and we wanted to sink them, but when it got dark they were brightly lit and they all had the American   flag on their sides." "They were neutral and we couldn't do anything." "Hitler had personally ordered that a signal be sent to U-boats expressly forbidding contact with American ships." "The frustration of Hardegen and his crew was mirrored across the U-boat arm that summer." "The failure of its codes compounded by the presence of an enemy it couldn't touch." "We had very strict orders to avoid anything that could cloud the relationship." "But one already felt in those days that the Americans were doing quite a lot that couldn't truly be reconciled with neutrality." "We shall give every possible assistance to Britain and to all who with Britain are resisting Hitlerism or its equivalent." "All additional measures necessary to deliver the goods will be taken." "By the summer of 1941 , half the food Britain imported and many of the weapons she needed to fight the war, were passing across the Atlantic from North America." "And Britain was pressing for more." "We one thing we hoped was that the Americans would come into the war." "If they did, that would be it, the war would be won." "Of course it has to be said there were many people who were very, very much in favour of Britain and who would be glad to get into the war of whom President Roosevelt was one." "The growing warmth of this friendship was demonstrated in August when Churchill steamed across the Atlantic for a shipboard summit with Roosevelt." "The President came bearing gifts." "British sailors were given cigarettes and fruit." "A taste of life as it was once lived at home." "American sailors were able to meet the British Prime Minister." "The two leaders gave voice to their unity of purpose in a joint service aboard the battleship, Prince of Wales." "Churchill got what he wanted." "Roosevelt agreed to bend the bounds of neutrality even further." "American warships would begin protecting British convoys in the Western Atlantic." "The USA declared a security zone." "An exclusion zone, and that was for us, of course, nonsense." "We regarded the whole of the Atlantic   as our operational area." "But the Americans attacked a number of   submarines in the Western Atlantic." "It regarded them as pirates." "The Admiralty was now confident that the tide of battle was turning its way." "Its figures showed that the in the last six months of 1941 , shipping losses had more than halved." "The U-boat was struggling to find targets." "When it did, it risked confronting the muscular neutrality of the United States." "But it was clear this stand-off couldn't last forever." "On October the 31st," "Eric Topp's U-552 was hunting in the waters south east of Greenland." "I came upon the convoy in the early hours of the morning and attacked immediately with two torpedoes." "The Reuben James was hit   and burst into flames and a hundred and ten men lost their lives in the icy cold water." "Oil spouted out of the ship into the sea and in places this was on fire." "Then, unfortunately, after the boat started to sink, her depth charges began to explode and that tossed the survivors high up into   the air." "They were thrown up to a height of fifteen metres and of course hit the water again in a very badly wounded state." "Topp's U-552, sank the first American warship, before there was officially a war to fight." "In the Atlantic at least, the United States was now at war with Germany in all but name." "I reported every detail of the attack to Donitz and he said nothing more than, 'lt's all right, you acted correctly.'" "Donitz approved, Hitler did not." "Topp wasn't disciplined, but Hitler still refused to rescind his orders." "No more attacks on American ships." "By December the U-boat war had almost grown to a halt." "But the issue was settled five weeks later." "Not in the Atlantic   but in the Pacific." "This is the Arizona writhing in death agony." "Awakening America to battle and rallying America to a new battle cry." "'Remember Pearl Harbour.'" "Hitler was surprised by the Japanese air strike at Pearl Harbour." "But in support of his ally he now declared war on the United States." "Donitz and his crews were delighted." "The entry of the United States into the war was, I would almost say, a relief." "We could now respond to what the Americans had already been doing to us in terms of hostile attacks." "Preparations began for 'Paukenschlag.' 'Operation Drumbeat'." "Now, at last, was an opportunity to breath new life into the faltering U-boat campaign." "Just five large U-boats were to spearhead the attack on the United States." "One was the U-123." "Hardegen and his crew set out for the new combat areas on Christmas Eve 1941 ." "A few of us were already wondering whether we would get back from there in one piece." "It was a fair way." "I had no charts for America." "I had a Knaur pocket atlas and in it there was a small city map   of New York." "That was all I had." "U-123's arrival would not go unannounced." "There was Ultra." "On January the 10th, 1942, a message was intercepted and delivered to Bletchley." "It was an order from Donitz to the Drumbeat boats." "It was clear an attack was building off the American coast." "But the eyes of the American Navy were still turned to the Pacific." "The warning reached the desk of its naval intelligence service, but no action was taken." "In those first days after Pearl Harbour it really was a pantomime." "But then you've got to remember the United States was a hell of a long way from anywhere else." "And Americans were not accustomed to think of people attacking them on their own shores." "On January the 13th, U-123 inched its way into New York Bay." "Operation Drumbeat had begun." "I had flooded the front tanks so that only the tower showed." "What America fisherman would recognise a German U-boat tower?" "I'd assumed that I would find a coast that was blacked out." "There was a war on, after all." "But ships were sailing with their navigation lights shining brightly." "We could see the cars driving along the coast road   and I remember we could even smell the woods." "I waited until the ships left New York, then I would sail behind them until they were in about forty, fifty metres of water and then sink them." "The night of the long knives." "A drumbeat with eight ships sunk, including three tankers." "If only there'd been ten or twenty U-boats here with me." "They would all have had successes aplenty." "Hardegen was able to report to U-boat Headquarters that American waters were teaming with ships unprotected by convoy." "The U-boat could sink at will." "We had expected there would be some successes at the beginning." "But we hadn't expected they would be as great." "That was, let's say, a nice surprise." "This was not what the Admiralty had anticipated when the United States entered the war." "Losses began to climb." "Forty-eight ships in January, ninety-five by March." "There was worse news." "On the 1st of February, 1942, naval intelligence was obliged to report that the flow of 'Ultra' was an end." "Bletchley had lost access to the key Enigma code." "The work dried up and everything stopped." "Nothing was happening at all." "And we were really rather desperate." "It had a very bad effect." "People walked around with long faces, particularly the cryptographers who were almost in despair." "Donitz had insisted on the change." "There were just too many coincidences." "Too many convoys missed." "Too many supply ships sunk." "A new fourth wheel Enigma machine had been issued to the Atlantic boats, and a new code, called Shark." "It was enough to ensure the Ultra tap was turned off just when the United States needed its help." "We were very, very miserable about not being able to get into the Shark, we knew that was much more important than anything else that we could do." "We knew what the sinkings were like." "On April the 8th, 1942, the tanker Esso Baton Rouge was passing along the coast of Georgia." "These were dangerous waters." "They'd become a favourite hunting ground for the U-boat." "After four months of war there was still no convoy protection." "Nor had most Americans woken to the new Pearl Harbour unfolding on their doorstep." "All the businesses, they wouldn't dim their lights   and a ship going up the coast or coming down, you're silhouetted against this light." "This was like a shooting gallery." "You know, you picture yourself sitting out there at about a hundred and twenty, a hundred forty thousand barrels of high octane gas, there's something to think about." "There were many who refused to sail on tankers." "They were an especially prized target." "In the first four months of America's war, more than fifty were sunk on the East Coast and in the Caribbean." "The Esso Baton Rouge was a little more than two miles offshore when her shadow was spotted by Hardegen's U-123." "Ba-woom, she says. I don't know how high up in the air I went because she was right under me, just about." "I don't know cos it knocked me out or what but when I come too I says, 'Holy mackerel.'" "You know the first thing out of my mouth?" "First thing out of my mouth, 'Please God, help me now.'" "The first thing out of my mouth." "Nine days after the sinking of the Baton Rouge all tanker traffic on the East Coast was suspended." "The U.S. Navy was unable to protect shipping in its own waters." "It was fighting a war in two oceans." "And in the Atlantic it was losing." "I was a pretty sick cookie." "I'd come home, my mother would put the rubber mat in the bed, 'cos I was having such nightmares I'd wake up in a pool of water, sweating so bad." "Boy I'd get some doozies." "One time I was running down the hall hollering 'general quarters.'" "Do you believe it?" "The tin fish has surfaced and like all fish out of water is doomed if it remains there too long." "Much was made in the newsreels of an American counter attack." "The public was told of hundreds of hunt and destroy missions." "Of fifteen U-boats sunk in the first three months of the war." "Planes would come and drop a few bombs." "We would only   laugh about that because they were so far away they had no effect, but they always reported, 'l've sunk a U-boat.'" "Return to base." "Okay." "We were supposed to have been sunk three times." "Every time we sunk a ship we were sunk again." "The Americans needed   this as a consolation, the idea that they had done something." "But it wasn't true." "Despite the American planes, no U-boats were sunk in United States waters in the first three months of the war, and with tankers burning off the beaches, it was impossible to hide the failure of the Navy's response." "Operation Drumbeat breathed new life into the U-boat war." "Donitz's boats were sinking more than four hundred thousand tons of shipping a month." "Hardegen's U-123 alone, sank nineteen ships on its two patrols to the United States." "We were the ones who'd had the greatest success and the reception and the propaganda circus around us was correspondingly noisy." "I was a little embarrassed at times, because in fact we hadn't encountered much resistance." "The Donitz pinned the Knight's Cross on me on the deck of my boat." "That was, of course, a special moment." "Donitz had good cause for satisfaction." "Everyone wanted to be part of what the crews called 'the Great American Turkey shoot.'" "U-boat Headquarters didn't care where in the Atlantic the successes were won, just as long as more ships were sunk than the allies could build." "Donitz sent all the U-boats he could muster to American waters." "This was made possible by a new type of submarine, which thanks to the change in the Enigma code, was a well guarded secret." "U-boats were now able to rendezvous off the American coast with giant underwater tankers, loaded with up to seven hundred tons of fuel, food and torpedoes." "A U-boat could now double the length of its war patrol on the American coast." "Staff at the Admiralty were unable to contain their frustration." "There was sharp criticism of their American ally's failure to introduce convoys sooner." "The monthly total for June was to be the worst of the war." "One hundred and seventy three ships sunk." "These losses were threatening the whole allied war effort." "But for all the Admiralty's anger, its grim statistics had a new and disturbing trend." "A growing number of ships were being sunk many miles from the American coast." "U-boats had struggled to find ships the summer before." "Now they seemed able to find them even in the middle of the Atlantic." "When a ship was sunk here the chances of survival were slim and the U-boat crews knew it." "I suddenly realised that about a hundred feet away was this thumping great U-boat." "And um, the machine guns were manned, the - she had a couple of a canon, they were manned and we all thought that was - that was it." "Instead he asked someone to come alongside and er, he handed out er, bread, tins of butter and some first aid dressings and he said," " 'We will report your position after dark and good luck' and took off then." "I think it was the worst time, that first night, in many ways." "You began to think about er, how a few hours ago you were having breakfast   and you ought to be having a jolly good dinner now." "You're wet and icy cold." "Your backside would sit on the hard surface, wet surface, wet clothes, rocking, thrown about like that, you're never still." "Each mean got a quarter of this can of pemmican." "It's - it's like fruit and chopped up meat, a lot of coconut, coconut oil   pressed into like a little sardine can." "And they'd get two malted milk tablets and they'd get this little container of water about the size of a shot gun shell, they got that twice a day." "And that was our ration." "You see a wave the size of a house coming towards you in a   open boat with seventeen chaps in it and you - you think, this one's going to come over the top and you thought, this is it this time." "We - we had two helmets in the boat, so there was always two men with those helmets bailing water." "You just kept at it because if you gave up you were done and you knew this." "As the days wore on, your tongue started to swell and all you thought about was when was the water coming round, when   when was the water - you longed to drink something." "When I was a child I'd read Charles Dickens Christmas Carol and there's a lovely illustration in that book, the Ghost of Plenty." "He sat up in front of a   giant fire, log fire, with fruit and food and mulled wines and all sorts of things around him and every time I closed my eyes, I could see that." "From the summer of 1942, many of the merchant seamen forced to undergo this ordeal, were paying the price for a catastrophic British intelligence failure." "The breaking of the German Enigma codes was of immense value to the Admiralty and yet it was cavalier about the security of its own codes." "It relied on book ciphers." "Easy to use, but often easier to penetrate." "Little effort was made to disguise the code's 'indicator'" " the key for anyone decrypting a signal." "By the summer for 1942 the Germans had cracked the British convoy codes." "Their most successful U-boat pack attacks on our convoys were based on information obtained by breaking our ciphers." "The Germans were doing just about as well with our ciphers breaking them as we were doing with Ultra." "In fact at times they may be doing better." "Thousands of signals were sent to allied ships every week." "As much as eighty percent of those sent in one code were read by the Germans." "secret report written for the Admiralty after the war, admitted it had cost the country dearly in men and ships, and nearly lost us the war at sea." "By the time the U-boat returned to the convoy war later that summer, the intelligence advantage rested with Donitz." "He would use it to direct his packs against convoys deep into the North Atlantic." "A thousand miles or so away from land." "Before the end of three weeks, you know, we realised we were really in trouble, because the food was going down   and we saw all these fish with the - swimming around were sharks and these Pilot fish, they would swim closer," "real close to the boat and you just pitch them in the belly and throw them in the boat." "And you probably missed fifty of them before you got one." "Your tongue which was black and your lips were black and these   boils, which are all over your legs, painful, er, 'cos your legs were in salt water most of the time." "We would read the Testament," "New Testament, we had the book with us." "We'd read that two or three times a day." "Well I think it kind of   settles your mind." "I - l can remember being at home and playing tennis in fact and er, and I wasn't   in that boat for quite a long time." "It was uncanny, really." "This guy, we found out he'd been torpedoed before and he, mentally he was not with it and he'd lay his money out in the boat and he'd" " he'd give somebody a five dollar bill and tell them to call the water taxi, he wanted to go ashore." "And then we got in this terrible storm one night and as we were all doing our thing   he just stood up in the middle of the boat and he jumped." "He just literally jumped right out of the boat and we never saw that man again." "You know it was kind of heartbreaking, he'd been through so much   and then he - he just decided he'd had it." "It was a grey, cold, North Atlantic day and somebody saw this um, shape on the horizon and it was an Icelandic trawler." "And its name was Surprise." "Some surprise." "We were put on to the mess deck in hammocks and the crew of the Snowflake I" " l can't speak enough." "To us it was emotional." "To them, they'd picked up survivors before and it meant really not that much to them until such time as they were   finally understanding what we were telling them, how long we were out there." "Then they couldn't believe it." "U-boats sank a staggering eleven hundred ships in 1942." "More than thirty thousand British seamen were forced to take to lifeboats." "Ten thousand lost their lives." "It was the costliest year of the war at sea, so far." "At the beginning of the war," "Donitz had announced that with enough U-boats he would secure victory in the Atlantic." "Then he'd commanded just fifty-seven." "Now, at the start of 1943, he had three hundred and ninety-three."