Blood, Tears and Folly: An Objective Look at World War II. Len Deighton

racing white wake of his periscope, sped towards it and dropped a pattern of depth charges. But Lemp escaped and without delay came back up to periscope depth just in time to see the destroyer coming at him. The second scatter of depth charges was close. The underwater explosions stopped the electric motors, started leaks in the oil bunkers and sent the U-boat plunging downwards. Lemp ordered the tanks blown. This not only stopped the descent but brought U-110 back up to the surface with a boiling of water that got the immediate attention of the deck crews of all three destroyers. Flustered, Lemp failed to have the pressure valve released, so that when the hatch opened a great cloud of dust came pouring out of the submarine. So did the crew, who jumped into the sea with their captain.

      The captain of HMS Bulldog was shouting for a boarding party almost as soon as the mortally damaged U-110 surfaced. Ignoring the probability that the Germans had set explosives before abandoning ship, a 20-year-old sub-lieutenant, rowed out by five sailors, clambered aboard the slippery hull of the wallowing boat and went down into the dark interior followed by his men. They formed a human chain to pass back the codebooks, charts and, having unscrewed it from its mounting, the Enigma machine itself. With great thoroughness and an iron nerve the sub-lieutenant scoured through everything on the U-boat from charts to ‘art studies’. He searched through discarded clothes to find anything of value to intelligence from the contents of wallets to recreational reading matter. It took three or four hours to get everything valuable aboard Bulldog.

      From the water Lemp watched the British go aboard his command. Realizing that his detonators had failed and knowing that he was responsible for the destruction of the Enigma machine and all the secret material, he seems to have deliberately allowed himself to drown. (Ex-U-boat men – and at least one account²⁴ – say that Lemp swam back to the U-boat to sink her and was shot by the British boarding party as he climbed on to the deck, but I find no evidence to support this allegation.)

      HMS Bulldog’s captain tried to tow the U-boat back to port but failed. He showed masterly restraint and impeccable good sense in keeping his extraordinary success secret, so that no news of it could leak back to German intelligence, but he little knew what a tremendous coup he had brought off. The men from BP had never had such a wonderful collection of data: a new machine, spare rotors and a list of the prescribed rotor settings for the length of the U-boat’s cruise – three months – and a mountain of helpful material that enabled them to read most Enigma machine messages in the code Hydra for the rest of the war. It also helped with the big warship code Neptun and the Mediterranean codes Sud and Medusa.

      The ups and downs of the Enigma struggle meant that messages were sometimes read almost immediately and at other times there were long delays. Most messages were never read. The naval Enigma was the most difficult to crack and many successes came from captured current German keys. Without such helpful clues the German naval secrets could seldom be tapped. And yet it was only because Bletchley Park had been set up with its Enigma machines and bombes that the captured keys could be used.

      But Enigma was only one part of the Atlantic battle. Nothing was more decisive than the rate at which merchantmen and escorts could be constructed in British and North American shipyards. The construction of U-boats was equally telling, and so were the global demands that took warships and U-boats to other parts of the world. The weather played a part, and so did the successes of the German B-Dienst, the service which intercepted British signals. The availability of Allied air cover and of long-range aircraft, and, the extent of Luftwaffe reconnaissance and anti-shipping operations, influenced the monthly figures, as did the operations of German surface raiders. The rationing of food and petrol was vital to the struggle, as was the improving technology of anti-submarine weapons – such as the hedgehog depth-charge thrower – and the use of better explosive charges. Just as deadly in effect were airborne and shipborne radar and, perhaps most important of all, ‘Huff Duff’, which provided ever better ‘fixes’.

      The Germans never suspected that the British might be reading their Enigma traffic on a regular basis. The chief of the German navy’s Signals, and the head of the Naval Intelligence Service, assured Dönitz that it was not possible to crack such machine codes. After the war Dönitz still believed them. To some extent of course this was true.

      By 23 June 1941 British penetration of the Hydra traffic had given the OIC (Operational Intelligence Centre, of which the Submarine Tracking Room was a part) a great deal of supplementary data, including details of all German inshore traffic and thus minelaying operations, as well as the routine messages that marked the beginning and end of a U-boat’s cruise.

      Enigma intercepts also revealed the positions of five tankers, two supply ships and a scouting ship positioned for the commerce-raiding cruise by Bismarck and Prinz Eugen. When plans were made to attack these auxiliary vessels, the navy decided to leave two of them – the tanker Gedania and the scout Gonzenheim – unmolested. To attack them all might prompt the Germans to guess their Enigma had been penetrated. By chance the Royal Navy happened upon those ships too, and so the whole lot was sunk. As feared, this massacre – five of the sinkings occurring over a three-day period – made the Germans investigate the possibility that Enigma was insecure. They decided that the spate of sinkings was probably a coincidence, but additional security measures were introduced just to be on the safe side.

      One of the planned measures was a fourth rotor for the navy’s Enigma machines. A shiny new Enigma machine had been recovered from U-570, which in August 1941 surfaced near Iceland and fell victim to an RAF plane. The Enigma machine had been built with an extra window, all ready for the extra rotor when it was issued. The sight of it sent a shudder through the personnel at BP, for the mathematicians calculated that it would multiply their already Herculean task by a factor of 26! They were right: 1942 brought the four-rotor machine and a year of darkness for the men peering into the German navy Enigma. Sinkings went from 600,000 tons in the second half of 1941 to 2,600,000 tons in the second half of 1942.²⁵

      A last word about Bletchley Park is a cautionary one. Considerable opportunities for intelligence gathering were neglected because the pre-war SIS took no interest in foreign radio transmissions other than messages. It wasn’t until 1940 that there was any attempt to intercept or analyse radar or radio navigation signals. GC&CS was responsible not only for cryptography and communications intelligence but also for safeguarding British communications. Whatever its glittering, and much trumpeted, successes at the former, its role as guardian was a chronic and dismal failure.

       The Submarine Tracking Room

      The Submarine Tracking Room used a wide range of incoming data. Anything that could possibly help was funnelled here. For the admirals perhaps the most disconcerting thing about this place, where Britain’s most vital battle was being fought and from which came the operational decisions that sent orders to the warships, was that by 1941 no regular naval officer was anywhere to be seen.

      The room was run by Rodger Winn, a 30-year-old lawyer with degrees from Cambridge and Harvard. He had drifted into this job as a civilian, after volunteering to interrogate enemy prisoners. Winn would never have passed a Royal Navy physical examination: childhood polio had left him a hump-backed cripple who walked with a limp. Neither would he have found favour in the peacetime navy, for he had limited respect for authority. Like many barristers he was a talented story-teller with a sharp tongue. The security of having a well paid profession waiting for him encouraged him to stand firm against authority. When a decision of Winn’s was challenged by an admiral, Winn put a vast heap of reports, sightings, charts and intercepts on to the admiral’s desk and politely asked him for his solution.

      When Winn joined the Tracking Room staff, the emphasis was on plotting the present state of the Atlantic battle, rather than predicting the future. But such was Winn’s talent for reading the minds of the U-boat men, that in January 1941 his boss was moved out of the Tracking Room and Winn was given sole command of it and made a commander in the Royal Navy Volunteer Reserve. And when in January 1942 he chose an assistant, it was another ‘civilian’, a bespectacled insurance broker from Lloyd’s.

      Most of the Tracking Room’s floor space was occupied by a seven-foot-square plotting