Physically, the machine and its rotor wheels usually remained under the tightest security, with the operator given specific instructions to destroy the components if capture seemed imminent. The key sheets and code books, sometimes printed and stored for a month or even a year in advance, required special precautions. At sea, where capture and compromise could occur at any time, ships stored the requisite setting sheets for a limited period, such as thirty to ninety days. They were heavily guarded, either in the captain’s safe or squirrelled away in his footlocker or the panelled wall of his cabin, or hidden in other parts of the vessel. On land, the shore-based facilities, depending on their function and position in the communications chain, could stock six or twelve months’ worth of sheets and code books, likely in the commanding officer’s safe. The German navy, like most of its counterparts, printed cipher materials in water-soluble ink so the writing would vanish if they were tossed into the sea by the crew.
On land or at sea, there were standard operating procedures calling for the destruction of the machine and its parts in the event of imminent capture: first, remove and dispose of the rotors; then pull out the plug-board cables; finally, destroy the machine completely or partially by physically smashing its components or by disposing of it in a way that would render recovery impossible. In some German shore-based facilities, such as in the heavily defended town of Dieppe, the Kriegsmarine trained special units to prepare for an attack: they would quickly gather all the machines, along with the code and cipher materials, and destroy them.
Given all these precautions, it is not surprising that the German high command placed such great faith in Enigma. Even if the Allies got a break, it would be limited in time and scope and therefore temporary in nature, meaning the Germans could simply let the current material expire, without going to the enormous expense of overhauling their entire signals system. Because of the time and energy required to wade through the data and decipher messages, they believed that any captured materials would yield vastly outdated information. According to the pre-war estimate, one Enigma machine could produce 10.5 quadrillion possible keys for each message, meaning it would take a thousand enemy cryptographers working with four captured or copied keys close to 1.8 billion years to test them all.15
However, the Nazi high command, despite some brilliant and maverick minds at work in their own code-breaking organization, Beobachtungsdienst, or B-Dienst for short, suffered from an institutionalized anti-intellectualism and arrogance that gave the British the time and space needed to conquer Enigma. The British harnessed their greatest intellectual resources right from the outbreak of war in 1939 and put them to work at Bletchley Park. They challenged these people to overcome the staggering odds and take the science of cryptography to levels never before imagined. To make an analogy, they stood the same chance of defeating the three-rotor naval Enigma in 1939 as an individual would have in winning a national lottery once a day, every day, for nearly one hundred years. Nevertheless, by mid-1941, the cryptographic team—led by the legendary Alan Turing, Peter Twinn and Dilly Knox, among many other stellar minds—had done just that. The journey to this great accomplishment was anything but smooth, however, and when Turing first took on the project with his team in Hut 8—the Bletchley hut devoted to cracking the naval Enigma ciphers—he did so under a cloud of pessimism.16
Fortunately, help for the Bletchley Park cryptographers came in several forms. First, they received tremendous aid from the work of exiled Polish cryptographers, who had pioneered the cryptographic assault on an earlier version of the German army Enigma in 1932 and who turned their work over to the British and French just before Germany invaded their country in 1939. The Poles invented the original Bombe, a high-speed electromechanical device designed specifically to attack Enigma encryption. It in turn was improved upon by Turing, who created the first machine able to decipher the German encryption—something that Fleming would have appreciated, given his fascination with Charles Babbage’s pioneering work in computers and cryptography.17
“The Prof”: Dr. Alan Mathison Turing was a wild and eccentric genius among code-breakers. Often called the ‘father of modern computing,” he was a brilliant mathematician and logician who developed the idea of the modern computer and artificial intelligence. Turing’s work helped develop the Bombe, an electromechanical device used to decrypt Enigma-encrypted messages, and later the world’s first computer—the Colossus. His tragic death, whether suicide, accident or murder, has never been satisfactorily explained, although urban legend claims his death is reflected in the Apple logo: after being convicted of an illegal sexual relationship with a man a few years after the war, he was sentenced to chemical castration by hormone injection. In June 1954 he was found dead, after having allegedly bitten into an apple dipped in cyanide. (photo credits 3.3)
There were fundamental differences between the two designs. Unlike the Polish Bombe, which relied strictly on mathematical principles, Turing’s Bombe was based on “cribs,” or “cheats”—a system similar to possessing answers to one or more questions on the Times crossword which also hint at the solutions to other questions. In essence, the Bombe sifted through all the possible configurations of the three Enigma wheels, searching for a pattern of keyboard-to-lamp-board connections that would turn the encrypted letters into plain German.18 Although the Bombe worked in mathematical terms at superhuman speed, reducing the man-hours needed to a mere fraction of what the human brain alone would have required, in real time during a war it simply wasn’t fast enough. Each Bombe took days or even weeks to crack an out-of-date message from an Enigma key. Turing tried using one of his Polish-inspired inventions, “Banburismus”—a cryptographic process that in theory could speed up the machines by enabling code-breakers to narrow down the number of wheels that could have been in place when a message was sent. Still, without any bigram tables to consult, he had no matching pieces of German and English text to help him reduce the odds.
Then a most fortuitous pinch of material in Norway provided just what Turing required to solve the problem.
On April 26, 1940, the German armed trawler Schiff 26, disguised to resemble the Norwegian vessel Polaris, which was taking mines and torpedoes to German forces in Narvik, crossed paths with the British destroyers HMS Griffin and HMS Acheron. The destroyers quickly disabled the trawler and captured her crew before they could destroy their cryptographic documents. The haul, delivered promptly to Bletchley Park, was a godsend for Turing: it revealed the precise form of the indicating system, the plug-board connections, and the starting positions of the three rotors for a twenty-four-hour period. In addition, the operators’ log contained a significant stretch of plain text and enciphered material for the cryptographers to analyze.
These documents were the “cheat” they needed. Feeding the results of the Banburismus into the nascent Bombe, the result demonstrated, despite the out-of-date and essentially useless immediate results, that their overall deciphering approach had merit. Banburismus in itself was not a stellar leap forward, but it was still significant. As one veteran of Hut 8 recalled, it was “not easy enough to be trivial, but not difficult enough to cause a nervous breakdown.”19 Soon, however, the joy and relief felt within the sparse confines of Hut 8 turned into despair when the Germans changed their bigram tables just weeks later, in June of that year.
Ideally, the solution lay in building more Bombes that could work together, harnessing their collective might to break into intercepted Enigma messages. But each Bombe was extremely expensive and difficult to produce, and the cryptographers in Hut 8 did not have time on their side. Additional Bombes would take months or years to arrive, leaving pinched material the only alternative to enable the British to attack German naval codes and ciphers.
Thus, with the stark reality of defeat facing them in 1940, the various sections that made up British intelligence, and specifically naval intelligence, knew they had to get what they needed by any means at their disposal—and as quickly as possible. For the great
mathematicians at Bletchley, Alan Turing and Peter Twinn, even a small pinch would again meet their immediate requirements. However, “if the whole bag of tricks was pinched,” Frank Birch informed Fleming, “there’d be no delay at all.”20 “Ideally,” he said, “those on board should not have been able to destroy anything,” or have time to get rid of “papers on their persons, or to throw anything overboard.”21 Birch, isolated at the Naval Section in Bletchley Park from the hub of the war effort in London, argued that alternative methods of capturing the essential materials should be examined and the concept of pinching continuously maintained. The Germans, he said, could “muck their machine about” at any moment, which would right away require another pinch. He demanded to know if there was “anything in the wind,” because “there ought to be.” 22
Alan Turing’s Bombe. In mathematical terms, it worked at “superhuman” speed. The Poles designed the original Bombe just before the Germans invaded Poland—a high-speed electromechanical solving device for Enigma. It in turn was improved upon by Turing, who created the first Bombe able to decipher the German encryption. As Jack Copeland describes in his book Turing: Pioneer of the Information Age: “The bombes were special-purpose electromechanical computers. At superhuman speed, a bombe searched through different possible configurations of the Enigma’s wheels, looking for a pattern of keyboard-to-lampboard connections that would turn the coded letters into plain German. At root, though, the machinery depended entirely on human instinct: in order to set the process going, a carefully chosen crib was required.” (photo credits 3.4)
A close-up view of the Bombe. Each row contains thirty-six rotating drums that simulate the action of the rotor wheels on the Enigma machine, effectively functioning like twelve Enigma machines. It took hours to set up and required great care in handling as it contained live electrical wires that could electrocute a careless operator. (photo credits 3.5)
Members of the Women’s Royal Naval Service, known as Wrens, skilfully operated the Bombe machines, which worked to speed up the code-breaking process. Allegedly, during a visit to Bletchley Park, Churchill thanked its hardworking, uncomplaining residents for “laying the golden eggs without cackling.” (photo credits 3.6)
The superficial treatment of Operation Ruthless in most past accounts portrays it as a lone-wolf operation, lacking in context or a sound basis, conceived by the impetuous Fleming and launched in cavalier style without any regard for its consequences. Recently declassified files clearly show that this interpretation needs overhauling. Once the Germans changed their bigram tables in June 1940, the Naval Intelligence Division, with Fleming in the lead, began a methodical and well-reasoned search for pinch targets within arm’s reach of English shores. Researchers began tapping into the wireless frequency and plain-language traffic of German salvage ships operating in the Channel, and before long they had established a “hit list” of vessels that possessed Enigma machines and related material or other codes that could be used as temporary solutions to the problem. The list focused on four types of vessels: S-boats (patrol boats) or German motor torpedo boats known popularly as E-boats; German torpedo boats that resembled mini-destroyers; aircraft security boats specifically dedicated to the rescue of downed flyers and aircraft; and minesweeping craft such as R-boats, M-boats and minesweepers that occasionally carried out rescues at seas.
By early September, all this research was collected in a special report on the “Activities of German Naval Units in the Channel.”23 Without doubt, it made an impression on Fleming. The report analyzed the strengths and weaknesses of each potential target. The habits of S-boats and E-boats were difficult to read because, generally, they were night predators, attacking British coastal convoys before returning to friendly ports by first light. They had no specific routine or patrol area, so the chances of intercepting them were slim. The larger torpedo boats had arrived in the Channel only recently, so little was known yet about how they would use Enigma. Aircraft security boats, which operated from the Dutch, Belgian and French coasts and engaged in daily rescues of Luftwaffe airmen, remained too close to the German-occupied coast unless they could be drawn out into mid-Channel and away from the view of potential witnesses to a pinch. In addition, evidence suggested they did not carry Enigma at all, but rather a minor salvage code known as Seenot, which was not yet readable by Bletchley. That left the minesweepers as the most promising prey. They generally hugged the coast and operated daily off Boulogne and Calais, carrying out their sweeping duties unless interrupted by a distress call from a downed plane in mid-Channel. 24 Again, because they had no regular positions, intercepting them depended on a surprise attack—if they could be lured farther from the coast.
“Is it too fantastic to suggest,” wrote Frank Birch in response to the report, “that efforts should be made to capture one of these in circumstances which would prevent the destruction of the Enigma Machine, attachments and papers?” He could not think how to attempt such a daring exploit himself, so turned it over to NID and the imaginative Ian Fleming. “We are incompetent to suggest the means,” he admitted, “but the elements would seem to be surprise, shrapnel and boarding.” 25 The result was Operation Ruthless, six weeks later.
In December, Birch, who was still wrestling with Enigma, put forward another proposal along similar lines. “Though operation Ruthless has been postponed on practical grounds,” he wrote, “the reason which caused it to be proposed has lost none of its force.”26 That month new information obtained from traffic analysis surfaced to suggest that aircraft security vessels, once believed Enigma-free, now carried both naval and air force Enigma materials, along with lower-level material corresponding to the German naval air code and the Seenot code. Immediately they became prime targets for a pinch.
Birch and his colleagues in the Naval Section at Bletchley Park suggested a plan that same month that was almost a carbon copy of Operation Ruthless, except that this time it would be carried out by ships instead of aircraft. In this case French chasseurs, or patrol boats, in the employ of the Free French Vichy would carry the commando strike force to its target. The first victim decided on was the Bernhard Von Tschirschky, an 880-ton seaplane tender operated by the Luftwaffe. Travelling under cover of darkness or in the obscurity of last light, the chasseur would approach the Von Tschirschky using the appropriate signal to announce that it had wounded on board in need of immediate attention. Having learned the commander’s name from an intercepted lower-level signal, the organizers in Naval Section suggested that the boarding party should shout out to him in perfect French or German as they approached, to gain the confidence of their intended victims. Once close enough, the raiders would open fire with their submachine and deck guns in an effort to panic and scatter the crew, followed by a tear-gas attack to incapacitate all aboard and prevent “destruction of the books and alteration of the settings of the Enigma machines.” The planners placed great emphasis on this aspect of the mission, directing that the plug settings, locked in position by the commander, be left in place.27
In the end, the suggested operation against the Von Tschirschky was shelved, just as Ruthless had been. In a series of terse letters, the furious Frank Birch urged the head of Bletchley Park, Commander Alastair Denniston, to act aggressively towards the naval Enigma problem, telling him, “The present position is a nightmare … and it is wearing the life out of me … Not enough is being done to break German naval ciphers.”28 Birch’s frustration boiled over to include shots at the Admiralty too, which he accused of foot-dragging, even though Fleming and his section had provided clear evidence of the type of material to be pinched and where it could be found: “The long and short of it is that the Navy is not getting a fair dose.”29 Birch’s solution went straight to the heart of the problem. He chided:
Cryptographers at their present rate of advance … will trundle along, getting out odd days, but at ever increasing intervals from the present unless they are given either a pinch or a very large number of bombs [sic] … Well, the issue is a
simple one. Tot up the cost and the difficulties and balance them against the value to the nation of being able to read current Enigma. The value of the latter has been put at 1,000,000 a day. Could the cost of any number of machines, plus the difficulties of making and running them, exceed that value? … I have never been in favour of the very melodramatic Operation Ruthless, but there are many ways of trying to pinch a small craft intact—it was done in this last war, so why not in this? It certainly is not a forlorn hope, it only needs perseverance.30
Despite this bitter disappointment for the cryptographers at Bletchley Park at the end of 1940, it seems from the Von Tschirschky file that Ian Fleming and the Naval Intelligence Division did learn something of significance from contemplating the attempt. While tracking the movements of this seaplane tender, they came to realize that all ships at sea using Enigma needed to communicate with shore-based facilities strung along the Channel coast, which made these ports, with their naval headquarters and signals equipment, prime targets for a pinch as well. They also saw that vessels like the Von Tschirschky, as well as other types of hotly desired ships, maintained an operational course that started at Brest and made a pit stop in Cherbourg, before pushing on to their terminal in Dieppe.
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