Decoy (5 page)

Watts put the pencil back in the jam jar which, Ned noticed for the first time, contained a dozen more, all well sharpened. He took a deep breath.

‘You haven’t put two and two together?’

‘No, sir: I can’t even find any twos.’

‘Enigma, my dear Ned, is the name of the German cipher machines.’

Ned groaned. Diabolical cunning, indeed! ‘I can see why the PM wants us to get one — and an instruction manual, too!’

Watts shook his head. ‘No, it’s not that: we’ve had an Enigma machine since the war began. We’ve been listening into German traffic for many months and the cryptographers have been breaking most of the ciphers within hours of the signals coming off the machine.’

‘What am I and my diabolical couple of dozen men supposed to do then, pinch a patent Enigma oil can?’ Ned was startled, puzzled and, for reasons he could not quite identify, apprehensive.

‘Keep that grin on your face for as long as you can, Ned, while I tell you something about our Enigma machine. “Machines”, I imagine, since we’ve built more. From what I hear, the Poles pinched one from the Germans before the war and passed it to the French, and we managed to get it out of Paris just before France fell, so the Germans still don’t know we have it. Hence the L tablets if any of you are captured.’

‘Pity we didn’t keep Asdic to ourselves,’ Ned grumbled. ‘Giving the French the finest submarine detection device in the world means that after the Toulon debacle the Germans found out all its weaknesses.’

To Ned’s surprise, Watts shook his head. ‘Yes, I agree it was unfortunate that as a matter of honour the French did not destroy the Asdics before surrendering their ships, but have you ever thought about the Germans trying out their U-boats against the captured Asdics and after discovering its limitations, designing new attack tactics? They found out they are quite safe if they get below a deep layer of cold water because the Asdic ping won’t penetrate. They discovered Asdic can’t operate if the hunting ship is going at any speed because of the dome, and so on?’

‘Yes, I’ve thought about it, sir. But…?’

‘Have you ever thought it strange that the Germans did these trials in 1940, a year after the war began, and yet their resulting tactics caught us by surprise — we who had invented the bloody thing back in 1937 or ’38?

‘In other words, Ned my lad, no one in the Admiralty faces up to the fact that we were so dam’ pleased with ourselves for inventing a machine that went “ping” and listened for it to echo back from a submarine with a “ding” that we never did proper trials
against
it.
Why
didn’t we know about thermal layers?
Why
didn’t we design a proper dome?
And
design depth-charges that can be fired ahead like a shell and sink quickly, not drums that are dropped or lobbed over the side and sink so slowly they give the U-boat time to get away? I’ll tell you, Ned, and to hell with the Board of Admiralty. We were so smug that we thought Asdic was the
complete
answer. Asdic meant no U-boat could survive against a ship fitted with it: never again would we have the terrible merchant ship losses of the First World War. The Admiralty thought it was to a destroyer what a telescopic sight is to a sniper or Spanish fly to a seducer.’

Ned had never considered that aspect, and he realized that Watts spoke with the bitterness not of a destroyer man jeering at submariners, but of someone who hated the stupidity of authority — which meant both the Admiralty and the Treasury — which cost lives when the fighting started.

‘It’s an old story, sir, and the Merchant Navy chaps have suffered most from it. Remember those lifejackets made of cork blocks to Board of Trade specifications, which broke the wearers’ necks when they jumped from sinking ships? Then the Ministry replaced them with thick waistcoats of light cloth filled with kapok. The poor devils in the merchant ships have long since found out that diesel fuel — always plenty of that floating on the water when a motorship sinks — penetrates the kapok so that in twenty-four hours it sinks. Those lifejackets are still standard issue. Lifeboats — they’re the same design as the one rowed by Grace Darling, and in average bad weather they’re impossible to get away from a sinking ship using only oars. Even a small merchant ship has four lifeboats — why isn’t it compulsory, in peacetime let alone war, that at least one boat has to have an engine? After my trip in a merchant ship in that convoy business I saw enough to want to send the last half-dozen presidents of the Board of Trade to sea on a sinking raft, along with their criminally stupid permanent secretaries. Anything with “Board of Trade Approved”, or “Approved by the Ministry of War Transport” is designed by moronic landlubbers, made by profiteers, useless and probably dangerous at sea.’

He stopped, red faced and embarrassed, but noticed that after this outburst the queasiness had gone from his stomach and he was no longer perspiring.

‘Well spoken, Ned. Pity this isn’t the House of Commons. Still, remember the civil servants’ union kept Wrens out of the Admiralty for months and months by claiming it was a “civilian” establishment and therefore all the paperwork should be done by their bloody members, and don’t get saddened. All through our history, if you read carefully enough, at least a fifth of the population is really working for the enemy, whether they realize it or not. Useless lifejackets, out-of-date lifeboats, torpedoes unchanged since the last war and leaving a trail of compressed air while the Teds have electric ones, the same rifle and bayonet, no decent tanks — and we had to learn tank warfare from the Germans, who learned it from the books of one of our chaps, Liddell Hart, and that Frenchman, de Gaulle…

‘Quite apart from all that, the standard light machine gun issued to the British Army is called the Bren, after the Czech town of Brno, whence it came; the standard light anti-aircraft gun issued to the Artillery is the Swedish Bofors; the 20 mm cannon fitted to our fighters is the Oerlikon, which I believe is Swiss.

‘We won’t embarrass anyone by mentioning the disastrous British-designed anti-tank rifle, which is even too awful for the Home Guard with their pikes, nor mention that we don’t have our own anti-tank gun. Our tanks are more suitable for storing water. In fact all we can be proud of are the Tribal class destroyers and one class of cruisers. For this happy state thank senior permanent civil servants of the Treasury, Foreign Office and the three services, and that pipe-smoking scoundrel Baldwin, who instead of being impeached was created Earl Baldwin of Bewdley. Baldwin of Lewdly, more likely. But…’ Watts made an effort to concentrate on the subject, ’we were discussing Enigma.’

‘Enigma,’ said Ned, ‘and the fact that the Germans don’t know we have it.’

‘Yes, that’s its value. The Luftwaffe seems to hate landline telephones: probably because the Resistance keep cutting the wires. Anyway, it bungs most of its traffic on the wireless, using Enigma: the targets for tonight, the losses last night, how many airmen in a particular squadron have contracted clap, and so on. All this is sent in various comparatively low-grade ciphers, of course. The Wehrmacht is not so good — the soldiers use the telephone more. But the Navy — the only way of communicating with a ship at sea is by wireless…’

‘But surely they can keep wireless silence most of the time?’

‘The U-boats can’t, obviously. The German Navy uses about a dozen ciphers. The main one is Hydra. It started off at the beginning of the war as the one for German ships in the North Sea and Baltic, but by the time the Germans occupied Europe it was being used for all their operational U-boats — ’

‘And we can read it?’ Ned exclaimed.

‘Yes. Don’t interrupt: you’ll see the effect in a moment. Medusa is the cipher used for U-boats in the Med. Commerce raiders — pocket battleships and the like — use Aegir. The big ships, the
Bismarck
,
Scharnhorst
,
Gneisenau
and so on, use Neptun when they’re at sea. Sud caters for surface ships in the Med. And when the
Oberkommando
der
Marine
wants to send a signal to a distant shore command (just as the Admiralty might send something to Suez) it uses Freya. And so on.’

Ned asked: ‘And we are picking up all this traffic and breaking the ciphers?’ The enormity of it, which could only mean that the Admirality was listening to every signal passing between the German Navy and its ships, left Ned almost dizzy, and deeply puzzled too.
Why were we losing the war at sea?

‘Picking up the traffic, yes, but not always breaking the ciphers quickly enough for the information to be of any use. It might take the cryptographers as little as twelve hours or as long as a week to break a particular signal — particularly Freya and Aegir, which are not used very often. That might be too long to make operational use of the information.’

‘What about Hydra, then?’

‘Ah yes, Hydra. Well, every U-boat operating in the Atlantic and the Mediterranean is fitted with a Mark II Enigma machine–’ he nodded his head and repeated, ‘a Mark II, not a Mark III, and issued with a manual. I should have explained that no matter which service is using Enigma, or what cipher is being used, the actual settings are changed at midnight. Thus in today’s setting, A might be K, in tomorrow’s setting it could be, say, W. The daily settings of the three rotors are printed in a manual for each cipher,’ Watts explained.

Ned was still puzzled. ‘As I understand it, Admiral Dönitz, known to his loved one as
Befehlshaber der U.boote
, or Flag Officer, U-boats, sits at his headquarters at Kernével, within cycling distance of Lorient. A U-boat on patrol in the middle of the Atlantic spots a convoy, her captain drafts a signal to
Befehlshaber der U.boote
giving position, course and speed, Heinrich gets out the manual and looks up the Enigma setting for the day, adjusts it and taps away, clickety-clack, and the signal whizzes off to
B der U
.’

‘Not quite,’ Watts interrupted. ‘Think of Enigma as merely a cipher typewriter which translates or scrambles the plain message into an Enigma signal in the Hydra code. Someone in the U-boat then takes the Hydra/Enigma version of the ciphered signal and then taps it out on a Morse key.’

‘Very well,’ Ned asked, ‘So
B der U
looks at his specially gridded North Atlantic chart, sees where the nearest other U-boats are, and drafts a signal for them to form a pack at a particular position, and sends it through his Enigma machine in Hydra code to those boats?’

‘Yes, as simple as that. And we’ve been able to pick up and read many of those signals going both ways. We have up-to-date approximate positions plotted of almost every U-boat at sea, and often know the quirks of the individual captains and wireless operators. Most good operators have an individual style which another operator can recognize, even though it’s all Morse!’

‘But if we know when a convoy has been spotted,’ Ned said, ‘surely we can see if it is steering for a particular concentration of U-boats?’

‘Oh yes, but if the escort of each convoy about to be attacked by a pack was suddenly reinforced, or made a major alteration of course (much more than the usual zigzag), it wouldn’t take long for Dönitz’s boys to realize we must be breaking their ciphers. Anyway, we don’t have nearly enough escorts to do any good. The best we can do, most of the time, is route the convoys through the safest areas.

‘Enigma and our ability to break Hydra does mean, though, that we can make the best use of every escort vessel, merchant ship and Coastal Command aircraft that we’ve got. When we can sink a U-boat we make sure Dönitz’s chaps never guess it was because we read any of their signals.’

Ned crossed his legs and cursed the hardness of the Ministry of Works Grade VII straightbacked chair, which seemed to have been designed by a Parliamentary committee advised by the Ministry’s Permanent Secretary and a distinguished orthopaedist specializing in the problems of incontinent turtles.

Where the devil was all this leading? It was fascinating that Enigma and Hydra told us so much about the German side of the Battle of the Atlantic, and how Dönitz was operating his U-boats, but how…?

‘What’s the problem then, sir?’

‘Simple, really. You now see where the Enigma machine and reading all the traffic fits in?’

‘Yes, perfectly.’

‘And you can see how important it is that we’ve cracked Hydra sufficiently to be able to decipher most signals to and from U-boats and thus know what’s going on out there in the Atlantic?’

Ned nodded. Watts must be getting tired because it was quite obvious that his explanation had been detailed and clear.

‘It took the cryptographers months to break Hydra, but they did it in about February of last year. Since then Enigma has been providing us with information about the U-boats which is absolutely vital. Even so, we’re slowly losing. Without it, we could lose the Battle of the Atlantic completely in the next three months.’

‘I can see that,’ Ned said. ‘But where does Mr Churchill and a third of our fleet and half our bombers come into it, sir?’

The skin of Watts’ face went taut and he suddenly looked old. ‘We’ve just discovered that the Germans will stop using Hydra any day now, and start using a completely new cipher, Triton. It’s also believed they are introducing a Mark III Enigma for U-boats which will have four rotors instead of three, and two spare rotors, giving a choice of four out of six. I’ll spare you the mathematics, but this gives them billions of different settings. The cryptographers estimate it might take at least a year to break Triton, and they don’t guarantee that they can do it at all.’

‘A complete blackout on what Dönitz is up to in the Atlantic, and at least a year to break Triton?’

‘Yes,’ Watts said. ‘That leaves us losing the Battle of the Atlantic, which means this island falls. Some stooge of Hitler’s will be installed in Buckingham Palace, all because of an extra Enigma rotor and a changed cipher. And the irony is that very probably the Germans are only changing the cipher as a matter of routine because what was their North Sea cipher at the beginning of the war has become the Atlantic operational U-boat cipher. Their tidy little minds have probably led them to prepare Triton so that Hydra can go back to North Sea use, though adding an extra wheel to the Enigma machine is probably for security alone.’