For his first step, Marian Rejewski was able to discern how the ‘indicator’ of each message – the starting position of the three rotors in the Enigma machine when the cipher clerk begins encryption – was arranged. There were repeating patterns, showing that the first six letters in every transmission were in two groups of three. Three letters implied something, something like the three starting positions of coding rotors. He had reached this degree of understanding without even seeing an Enigma machine.
Maksymilian Ciężki could see that his faith in Rejewski was not misplaced. After his success with the message settings, Ciężki brought Rejewski a wooden box. Inside the box was the commercial Enigma machine which Polish intelligence had bought a few years back. ‘And, Mr Rejewski, if you would be so kind, I should like you to work on this problem in the daytime as well. I’m afraid you will still not be able to discuss the matter with any of your colleagues, though.’
‘Yes, Mr Captain.’
Now Rejewski had a room of his own. It was small and somewhat less agreeable than the shared space which he had had at first, but better than a cubicle and he could concentrate. Rejewski was also told that the machine which the Wehrmacht were using was different: there were differences in the wiring and in the rotors, and, most difficult of all, there was a plugboard on the front of the machine. Rejewski was given a copy of the operating instructions – part of the haul from Hans-Thilo Schmidt, of whose existence Rejewski remained wholly unaware.
Now equipped with the basic structure of the machine, Rejewski could assign labels to each of the parts that scrambled the letters of the alphabet. There was the plugboard. There was the wiring connecting the plugboard to the ring of wires where the electric current entered the bank of three rotors. Then there were the three rotors themselves and finally there was the reflector which turned the current round and back through the rotors. Representing each element of the scrambling mechanism by an algebraic label, Rejewski could then draw up a set of simultaneous equations in several unknowns, where the unknowns were the permutations carried out by the different elements of the machine.
Rejewski was puzzling over his equations when, on 9 December 1932, once again Maksymilian Ciężki came to call. In his hand he was bearing a photographic copy of the actual daily settings used by the Germans during September and October. ‘Now,’ recalled Rejewski, ‘the situation changed radically.’ Since the table of settings included the connections of the plugboard, one of the unknowns had dropped out of the equations.
There was, however, still one feature of the machine which was – at that time – beyond the analytical genius of Marian Rejewski. This was the way the plugboard was wired up to the ring of twenty-six wires at the right-hand end of the bank of three rotors. In the commercial Enigma machine, the typewriter keyboard letters Q, W, E, R, T, Z etc. were wired directly to the letters A, B, C, D, E, F etc. on the entry ring. Not so with the military machine: some other arrangement had been chosen. In the first place, there was a plugboard interposed between the keyboard and the entry ring. The twenty-six wires leaving the plugboard were connected in some fashion to the twenty-six contacts on the entry ring. There were twenty-six factorial (26×25×24×23×…) possible ways of doing that: a horrendously large number containing twenty-seven digits if written out in full. Marian Rejewski, however, guessed that a simple arrangement might have been chosen; after all, the Germans were, if nothing else, methodical. Maybe Q was wired to Q, W to W, E to E, etc. And, miraculously, that seemed to have been the choice the designers had made. ‘The very first trial yielded a positive result. From my pencil, as by magic, began to issue numbers designating the connections in [the right-hand] rotor.’9
At the end of September, the Germans swapped around the rotors in the machine, so during October a different rotor was in the right-hand slot. More magic, and the connections of another rotor were disclosed. Marian Rejewski’s mighty pencil had started to bust the Enigma box wide open.
• • •
Mürren is a small village, clinging unsteadily to a rock terrace above a vertical 900m drop into the Lauterbrünnen Valley in Switzerland. It’s a tourist trap, with hikers in summer and skiers in winter. The scenery is stunning, with the Jungfrau and the Eiger and the Schilthorn all within easy distance. The only problem is getting a hotel room – let alone three of them – at short notice in January.
The aristocratic gentleman with perfect German had a commanding mien as well as ample charm. The hotel staff would be only too happy to oblige. Perhaps the gentlemen and his lady wife would like to sit in the lounge while everything was made ready? Rex took a large brandy and settled into a large armchair to admire the view. Soon enough, two more gentlemen arrived: Messieurs Barsac and Saint-Georges from France. And, eventually, on the very last cable car up from the valley, a third, bearing an elegant suitcase of fawn-coloured leather.
The 1930s were being kind to Hans-Thilo Schmidt. His liaisons with the French were paying off. Handsomely. Each package of documents he brought netted about 10,000 Reichsmarks and there seemed to be two or three opportunities a year to deliver these. By 1934, the pattern of payment was well established. Schmidt would receive a bland postcard; then he would know to take his false ID to the post office and claim an envelope from the poste restante service. In the envelope there would be a left-luggage receipt and this enabled Schmidt to collect a holdall from one of Berlin’s railway stations. A holdall containing his cash. Meanwhile, he’d been taught to write letters in invisible ink (no more complicated than dissolving salt in water; steam and starch would reveal the writing), to arrange meetings using more blandly worded postcards and to conceal the source of his unexpected wealth.
The French were worried about the cash. Too much cash might draw unwanted attention to their asset. And there was no chance that Hans-Thilo Schmidt would save his cash. For him the cash was there to be spent: on wine; on girls; on nice clothes; on all those things which showed just how he was making a success of his life. So, between them, Rex and Schmidt manufactured a laundering scheme. Hans-Thilo had studied chemistry. He borrowed some money from the bank (and from his ever-compliant military brother) and bought himself a soap factory. All the cash could now be explained as profits from the business. And the real business, the really exciting business of lifting secret documents, could now be done using a smart, expensive case of fawn-coloured leather.10
While Bertrand was once more banished to the bathroom, Rex, Hans-Thilo Schmidt and ‘Saint-Georges’ (in fact Major Guy Schlesser, a fluent German speaker from French intelligence) enjoyed a brandy in Rex’s suite. Rex asked politely about the soap enterprise; Schmidt wanted to talk about something else. He had a new role. The French looked disappointed. The flow of information might be about to dry up just as they had got the plumbing fully operational. Schmidt smiled, ‘I have been given responsibility for liaison between the Cipher Office and the Forschungsamt.’ Neither Rex nor Schlesser had the first idea what the Forschungsamt might be. None of the belligerent nations that made up the Allies in World War Two – a war which, in January 1934, was a world away from anyone’s imagination – ever found out about the Forschungsamt until after the war was over. Except the French, who found out on 5 January 1934. The Forschungsamt had been set up in 1933 as the, ‘research bureau of the Reich air ministry’. It reported to Hermann Göring, who wore so many hats it was probably irrelevant whether he was Commissioner of Aviation, Minister without Portfolio in the Reich government, Minister of the Interior for Prussia, or just the second most powerful man in the country. The Forschungsamt was Göring’s own personal intelligence service, ‘the richest, the most secret, the most Nazi, and the most influential’ of all Nazi Germany’s proliferating intelligence services.11 In being brought into the Forschungsamt, Hans-Thilo Schmidt had been given access to Germany’s highest-level secrets and here in Mürren he was offering to get those secrets for the French. Schlesser and Rex hardly knew what to say. Rex ordered more brandy.
From now on, Hans-Thil
o Schmidt was the number one asset of French intelligence. ‘He enabled us to follow step by step the German rearmament, to get intelligence on the highest level of German military policy, to know in advance all the most important projects until the war began.’12 Schmidt’s clandestine deliveries had just become much, much more important.
The deliveries were sometimes bizarre. In September 1933, Schmidt had hiked over the border into Switzerland with the secret codes in his rucksack. On a later trip, Schmidt brought papers which contained the new procedures for the Enigma machine, as well as the most recent monthly settings and a set of the army high command’s plans for neutralising the Czechoslovakian defences. In case he should be discovered with this incriminating material on him, Schmidt had asked the conductor on the train to take care of his bag – a wiser move than might be imagined, as Schmidt had also packed a selection of Bavarian salamis and charcuterie. As the central heating in the train wrought its effect, the temptation to look inside the bag diminished accordingly. One feels sorry for Captain Bertrand, stuck in a small hotel bathroom a few hours later with a camera and the documentation, delicately marinated in garlic and herbs.13
• • •
The first breakthroughs into Enigma had all happened very fast: Rejewski’s work had all been completed within a matter of weeks. Then he could turn to a rather more important personal problem, which was how to cement his relationship with Irena Lewandowska. It was 1933 and Marian had known Irena for years and years, but distance and work challenges had stood in their way. Rejewski’s persistence eventually paid off, though, and they were married, in Bydgoszcz, on 30 June 1934.
Unlike his celebrations with Irena, Rejewski’s cause for happiness over his progress against the German encipherment machine was, in fact, incomplete. Not a single message would be deciphered unless the Poles could find out the order in which the three cipher rotors were being put into the machine, as well as which of the twenty-six starting positions each rotor was in. The easy solution was to look into Hans-Thilo Schmidt’s rucksack to find the monthly settings which he routinely supplied in his meetings with Bertrand. But the more recent, more aromatic gifts finding their way to Gustave Bertrand did not continue their journey to Rejewski’s office in the Saxon Palace. For reasons we no longer know, Ciężki and Gwido Langer had decided to keep the team up to the mark using wits alone, rather than the materials procured by French intelligence.
Marian Rejewski was not daunted by the challenge of the settings. He had already observed that the preamble of every German message was structured as an ‘indicator’ of three letters, repeated and then enciphered. The idea behind repeating the indicator was that bad atmospheric conditions or other difficulties with radio reception might garble the indicator. Having it sent twice provided a back up. However, repetition of the indicator – enciphering the same three letters twice – gave Rejewski a tiny chance to discover what the indicator was. He noticed that he could follow a trail of letters from one encrypted indicator to another, and that the trails would eventually join up into loops he called cycles.* These cycles were ‘characteristic’ of the combination of rotors and the order in which they had been put into the machine. Finding the characteristics was the way the Polish code-breakers would uncover the settings being used by the Germans to keep their signals safe from enemy eyes.
Moreover, the German operators were being daft. They seemed to be an unimaginative bunch, choosing for their three-letter indicators adjacent keys on the Enigma keyboard, like QWE, or even repeated letters like QQQ. Such simple indicator patterns could be guessed by Marian Rejewski and other members of the team. After Rejewski’s great breakthrough, it became clear to Maksymilian Ciężki that Enigma decryption was a real possibility and the ban on sharing the nature of Rejewski’s special problem was lifted. It was only lifted by a tiny amount, but now Rejewski was not working on his own. His erstwhile Poznań classmates Jerzy Różycki and Henryk Zygalski were brought in on the secret and began to contribute their own thoughts to the problem of indicator-finding and the decryption of intercepted radio telegrams.
They rapidly realised that the potentially huge complexity of the Enigma machine could be distilled into something much simpler. If you examined only a short sequence of encrypted text – like the indicator, for example – the chances were that only one thing was changing from one letter to the next and that was the ‘fast’ right-hand rotor of the machine. The other two rotors and the reflector were just processing inputs in the same way, every time. So if what came out of the right-hand rotor went into the middle rotor at ‘K’ and came out at ‘P’ in position 2, anything coming out of the right-hand rotor at ‘K’ must always get converted to ‘P’ (and vice versa) at any other position in the sequence.
The ‘static’ behaviour of the middle and left rotors between turnovers (turnovers occurred only when the right-hand rotor had rotated enough to cause a simultaneous rotation of the middle rotor) allowed the code-breakers to devise new techniques for finding the rotor order and revealing the content of encrypted messages. The first technique they devised was called the ‘grille method’ because it used a sheet of paper with slots cut into it. Written on the paper was the transformation which the static part of the machine would make, given an electrical input at any one of its twenty-six electrical connections; through the slot another piece of paper was visible, showing the possible transformations of the right-hand rotor. If the code-breakers could trace actual encipherments through the transformations shown by the two sheets together, and find common pairs of letters, that told them they had found the right-hand rotor and its starting position. A by-product of the grille method was that it indicated some of the switch-arounds done by the plugboard as well. To get the most out of the grille technique, the code-breakers began to put together a card catalogue of the permutations brought about by all combinations of the left and middle rotors and the reflector: incredibly tedious, detailed work, but worth it to get the results.
• • •
Antoni Palluth was also doing rather well in the early 1930s. His electrical factory, producing radio equipment and other high-tech kit for the Polish military, was (in contrast to Asche’s soap factory, which held itself together only through the munificence of the French Deuxième Bureau) a commercial success. It had exhibited an innovative 50-watt transceiver at a public exhibition in Warsaw in 1930. With the wow factor of miniaturisation, the transceiver brought in orders from the Biuro Szyfrów and the navy. The orders came in regularly, including large contracts for the installations of radio telegraphy stations in Gdynia and Bydgoszcz, for Hughes type-printing telegraphy apparatus in Wilno and Lwów, and more. The relationship between one of AVA’s owners and their primary customer might seem a bit cosy for some tastes, but the products were of good quality, were good value for money and were produced on time. Palluth’s competitors could not match all that. And the whole thing was above board: senior officers in the Second Department of the General Staff knew all about the role of Palluth and they were signing off the requisitions. With the orders flowing in, AVA outgrew its city centre premises, ending up in a new facility in the southern district of Warsaw called Mokotów, a location that would prove to be very convenient in future years.
In among the radio equipment, the factory was making some rather unusual machinery. These special machines needed squat, fat wheels with twenty-six contacts on either face, with finger-grips and the letters of the alphabet printed around the rim. Inside the wheels the contacts were connected by criss-cross wiring. The wheels were, in fact, not wheels at all, for, having found a way to unravel the set-up of the Enigma machine, the Poles had wanted to get on with the useful business of actually reading the intercepted messages. And to carry out decryption they needed a bit more than just Rejewski’s mighty pen and knowledge of the settings: they needed an actual Enigma machine. They had one, for sure, but it was the old commercial machine with the wrong type of rotors. So an order was placed with a secret, privately run electrical factory
to make some machines which would behave just like the Enigma. The factory was AVA, and it could be trusted with these top-secret orders because it was run by Maksymilian Ciężki’s friend and colleague, Antoni Palluth.14
So, apart from the fact that Adolf Hitler had come to power in 1933 and begun the transformation of his country into a vicious war machine, everything seemed to be going rather well. Perhaps still appreciative of the value of being able to decode enemy signals in their wars for independence, the Polish authorities recognised what they had in Ciężki and his team of specialists. Ciężki was decorated with the Gold Cross of Merit in 1933 to add to his 1928 Silver Cross and his war and regular service medals. The code-breakers were also paid handsomely. Little did they know that the fat pay cheques would leave a trail which might expose their secret work and even put their lives and those of their colleagues in mortal peril.
* See Appendix for a more detailed explanation
4
THE SCARLET PIMPERNELS
I have heard speak of this Scarlet Pimpernel. A little flower – red? – yes! They say in Paris that every time a royalist escapes to England, that devil, Foucquier-Tinville, the Public Prosecutor, receives a paper with that little flower designated in red upon it.
Baroness Orczy, The Scarlet Pimpernel
In 1934, rearmament and belligerence still lay in the future. Who, apart from Hans-Thilo Schmidt, could tell what Hitler’s new political programme would bring? Certainly, his first year of power showed that the election speeches had not been all bluster, but the policies implemented by the Nazi Party had, so far, been all domestically focused: suspending constitutional protections for citizens; removing Jews from public offices and schools; introducing a eugenics programme for people with disabilities; establishing concentration camps; and burning un-German books. However unpleasant all that might be, it was not, apparently, a threat to other countries.
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