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- Herausgeber: Biteback Publishing
- Kategorie: Geisteswissenschaft
- Sprache: Englisch
- Veröffentlichungsjahr: 2010
The extraordinary wartime exploits of the British codebreakers based at Bletchley Park continue to fascinate and amaze. In The Emperor's Codes Michael Smith tells the story of how Japan's wartime codes were broken, and the consequences for the Second World War. He describes how the Japanese ciphers were broken and the effect on the lives of the codebreakers themselves. Using material from recently declassified British files, privileged access to Australian secret official histories and interviews with British, American and Australian codebreakers, this is the first full account of the critical role played by Bletchley Park and its main outposts around the world.
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Praise for TheEmperor’sCodes
“Smith writes a real-life thriller that unfolds like a classic spy story. The heroes here are not dashing secret agents; instead, they are seemingly fanatically dedicated and patient plodders who pore over the myriad possibilities involved in code breaking. This is an engrossing and exciting recounting of an obscure but important facet of World War II.”
—Booklist
“Smith includes a fascinating step-by-step explanation of codebreaking … A fine contribution to the genre.”
—KirkusReviews
“Smith portrays the sometimes bitter competition between American naval and British military personnel … all in all, it makes a great story and one of importance, since many historians believe that through their codebreaking efforts the Allies were able to shorten the war by as much as two years.”
—LibraryJournal
“Michael Smith’s book tells the riveting story of the breaking of the Japanese codes. It is an enthralling tale, the stuff of John le Carré, yet true. Smith’s impeccable research is highly detailed, and he draws on interviews with many of the remarkable codebreakers to give the narrative a human angle, presenting it more as a living chronicle and less as a historical study.”
—DailyTelegraph
THE EMPEROR’S CODES
BLETCHLEY PARK’S ROLE IN BREAKING JAPAN’S SECRET CIPHERS
MICHAEL SMITH
For Ben, Kirsty, Louise, Leila and Levin
CONTENTS
ACKNOWLEDGEMENTS
I am extremely grateful to all those former codebreakers and wireless operators who wrote to me or agreed to be interviewed for this project. Whether or not they are quoted in the book, their contributions played a major part in providing the information and encouragement I needed to complete it. I am particularly grateful to a number of people who went out of their way to help and encourage me. These include Geoff Ballard; Edith Becker; Geoff Day; Joan Dinwoodie; Joe and Barbara Eachus; Robert Hanyok; Margaret Henderson; Phil Jacobsen; Dennis Moore; Joe Richard; Harry G. Rosenbluh; Hugh Skillen; Joe Straczek; Jimmy Thirsk and Dennis Underwood. I am also grateful to Steve Kelley for sharing his expertise in Japanese machine ciphers with me and to Hilary Jarvis for her advice on the Japanese language. Special thanks are due to Hugh Melinsky; Norman Scott; Alan Stripp and Maurice Wiles for allowing me to quote from their own works and for their generous help and advice. I must also thank Ron Bonighton, Director of Australia’s Defence Signals Directorate, for kindly sending me a complete set of the Technical Records of the Central Bureau (a uniquely generous example of openness from a signals intelligence organization); Margaret Nave and the Australian War Memorial for allowing me to quote from Eric Nave’s original manuscript; the Library and Department of East Asian Studies of the University of Sheffield for permission to quote from the diaries of Malcolm Kennedy; Christine Large and the staff of the Bletchley Park Trust for their assistance and dedication to keeping the memory of the codebreakers alive; and last but certainly not least Ralph Erskine whose willingness to share his unrivalled knowledge of wartime codebreaking operations with me provided a constant lifeline.
I should also like to thank Charles Moore, Editor of the DailyTelegraph, for generously allowing me to take a sabbatical to write TheEmperor’sCodes; Sally Gaminara, Katrina Whone, Simon Thorogood and Sheila Lee at Transworld for their painstakingly professional work on this project; my agent Robert Kirby for his constant enthusiasm; and my wife Hayley for her patience and encouragement.
‘I believe most experienced cryptanalysts would agree with me that cryptanalysis is much closer to art than to science, and this is what makes the personal factor so important.’
JohnTiltman,ChiefCryptographeratBletchleyPark1940–5
Map
INTRODUCTION
The extraordinary achievements of the British codebreakers based at Bletchley Park in cracking Nazi Germany’s ‘unbreakable’ Enigma cipher are now widely known. This initially oddball collection of mathematicians, classicists and musicians performed unexpected miracles in the hastily constructed huts scattered around the grounds of an ugly mock-Tudor mansion in the small Buckinghamshire market town of Bletchley. The location had been selected in part because it was just far enough outside London to escape the threat of German bombs. But perhaps more importantly, it was midway between the ‘glittering spires’ of Oxford and Cambridge, from where most of the leading codebreakers had come.
The apparently amateurish nature of these early beginnings was epitomized by the actions of the codebreakers’ boss, Admiral Hugh Sinclair. His power over the Government Code and Cipher School, as the codebreaking operation was known, came from his role as ‘C’, the head of MI6. Perhaps surprisingly, this was in fact no secret within the limited confines of what was then described as ‘polite society’. But Sinclair was far better known among his immediate circle of friends for his reputation as a man with a taste for the high life. They christened him Quex after the title character in Arthur Pinero’s popular play TheGayLordQuex, who was described as ‘the wickedest man in London’.
This passion for the high life, and the fact that he had the personal wealth to fund it, dominated Sinclair’s dealings with the codebreakers – an earlier headquarters had been based in the Strand in central London, apparently for no other reason than that it was close to the Savoy Grill, one of his more favoured haunts. Unable to persuade anyone in government to pay for the codebreakers’ new country mansion, he dipped into his own pockets to buy it, immediately moving his favourite chef from the Savoy Grill to Bletchley Park to ensure that the codebreakers were well fed.
The result was an atmosphere at the highly secret Station X not unlike that of a weekend party at an English country mansion. The initial number of codebreakers in what was known for security reasons as ‘Captain Ridley’s Shooting Party’ was little more than 200. They lived in hotels in the surrounding towns and all initially worked either in the mansion itself or in a neighbouring boys’ school that had been commandeered for the purpose. When not breaking codes, or if simply seeking somewhere to contemplate their cryptographic puzzles, the codebreakers could wander through the lawned grounds of Bletchley Park, which included a maze, a lake and a number of rose gardens.
This brief idyll was shattered in part when the chef, unable to cope with the sometimes unusual demands of the more idiosyncratic ‘guests’ at Bletchley, attempted to commit suicide. But other factors were far more crucial in the transformation that was about to take place. As the Phoney War drew to a close and Hitler turned his attention to Western Europe, Britain’s back was very much against the wall. The need to break Enigma and to obtain a permanent source of high-grade intelligence on German movements was paramount.
Bletchley Park was soon swamped by new recruits, some of whom had experience within those British companies which were adopting more efficient business practices pioneered in America. By the time the pre-war British codebreakers such as Dilly Knox made the first British breaks into Enigma, Bletchley Park’s operations were already turning into a production line. The grounds increasingly resembled a building site. The maze and rose gardens disappeared to be replaced by prefabricated wooden huts in which worked thousands of people, the vast majority of them women.
The popular view of Bletchley Park, as an organization manned by brilliant but amateurish eccentrics, is misleading. Certainly early on the organization was dominated by eccentrics such as Knox and Alan Turing, but the incredible progress made by some of them not just with Enigma but also with the development of Colossus, the world’s first programmable electronic computer, gives the lie to suggestions of amateurism. The vast majority of those working at Bletchley Park were in fact neither amateurish nor eccentric, although many were indeed brilliant.
The work they did to unravel the intricate workings of the Enigma cipher machine is estimated to have cut around two years off the length of the war in Europe. But that is only part of the story. The British codebreakers were not just working on German codes and ciphers, they were breaking those of all of Germany’s allies in Europe: Italy; Hungary; Romania; Bulgaria; and initially, of course, the Soviet Union, as well as those of neutral countries such as Sweden, Spain and Portugal. The codes and ciphers of a number of non-European countries were also coming under the scrutiny of the British codebreakers, and the most important by far of these was Japan.
Almost a year before Pearl Harbor, the British and the Americans had agreed in principle to share their codebreaking resources. The two most important items on the agenda were the major machine ciphers of Germany and Japan. Bletchley Park handed over a paper version of the Enigma machine, providing the Americans with the start they needed to read the Wehrmacht’s messages. In return, the US Army gave the British its most precious piece of codebreaking equipment. The Purple machine had been built to decipher the messages passing between the Japanese Foreign Ministry, the gaimushoo, and its major embassies abroad.
Although it was nowhere near as difficult to solve as Enigma, or the later German enciphered teleprinter systems known collectively as Fish, the breaking of the Japanese ‘Type B’ diplomatic cipher machine, by a team led by the American mathematics teacher Frank Rowlett, was one of the great cryptographic achievements of the Second World War. The Americans christened the Type B system Purple and the intelligence derived from it was given the codename Magic, probably because William Friedman, the head of the US Army codebreaking operation, routinely referred to his cryptanalysts as ‘magicians’.
The amateurish eccentricity of the Bletchley Park operations is not the only myth to have grown up over the years. Enigma had originally been read not by the British but by the Poles. A team of Polish mathematicians, Marian Rejewski, Henryk Zygalski and Jerzy Rozycki, had managed to break it initially in 1933. While this was a brilliant achievement in its own right, it came at a time when German security procedures were very slack and the machines in use were at their most basic. Nevertheless, it provided the springboard that allowed the British to break the far more complicated systems put in place when the Second World War began.
Quite why the British had not attempted much earlier to break the Enigma machine, which was first introduced within the German armed forces in the late 1920s, is difficult to understand. It may be, as Josh Cooper, one of their number, said, that they really believed that, having had their codes broken easily by the British during the First World War, the Germans would never allow it to happen again. At any event, it was not until shortly before the Second World War broke out that the Government Code and Cipher School made any serious efforts to break the Enigma cipher. During the inter-war years, the British codebreakers had concentrated on what were regarded as the three main threats: Bolshevik Russia, widely perceived as being the biggest danger not just to the Empire but to civilized life itself; the upstart United States, still an uncertain force in world affairs; and the main threat to British colonies in the Far East – Japan.
This brings us to the other main myth: that the Japanese codes and ciphers were broken by American codebreakers. When Britain and the USA agreed to collaborate on breaking the codes of the Axis powers, a year before Pearl Harbor brought America into the war, the British were determined to keep control of the operations to break the Enigma cipher machine. It made sense that the Americans with their dominance of the war in the Pacific should likewise control the breaking of Japanese codes and ciphers, and a natural division of labour built up.
At the end of the war, details of how the US Army broke the Purple cipher were swiftly made public, to the horror of the British codebreakers. Almost certainly as a result of the rivalry between the two American services, news also leaked out of how the US Navy had broken the main Japanese naval code JN25, allowing its aircraft to shoot down the Commander of the Imperial Japanese Navy’s Combined Fleet, Admiral Yamamoto Isoruku. This publicity led to the lasting impression that the Americans had broken the Japanese codes.
By contrast, the British clamped down on any mention of the remarkable achievements of their own codebreakers, determined to ensure that they could continue to intercept the communications of other countries with impunity. It was not until the mid-1970s, with the publication of Frederick Winterbotham’s book TheUltraSecret, that sketchy details of how Bletchley Park had broken the Enigma ciphers began to leak out. News of the construction by Tommy Flowers, a British Post Office engineer, of the programmable computer Colossus only emerged much later, displacing the claims of ENIAC, an American computer which had until then been regarded as the world’s first.
The official files, still in the possession of Bletchley Park’s secretive successor GCHQ, did not begin to filter into the archives of the British Public Record Office at Kew, in south-west London, until the 1990s and those on the British codebreaking efforts against the Japanese were among the last to be released. Only now has evidence begun to emerge of how much work on Japanese codes and ciphers was done by the British codebreakers, not just during the Second World War but long before it even began.
During the inter-war years, several of the leading members of the Government Code and Cipher School became expert at breaking Japanese codes and ciphers: John Tiltman, an infantry officer who had won the Military Cross in the trenches of the First World War; Eric Nave, a Royal Australian Navy officer seconded to work with the British; and Hugh Foss, one of the true British codebreaking eccentrics, were breaking Japanese military, naval and diplomatic codes and ciphers long before the equivalent American codebreaking operation saw similar success. Nave was reading all of the early Japanese naval codes in the late 1920s; British codebreakers led by Foss were the first to break a Japanese diplomatic machine cipher in 1934; and it was Tiltman who first broke JN25, a few weeks after it was introduced in the summer of 1939.
The Americans, working independently, later came to make their own breaks into the Japanese codes and ciphers. But they were hampered by their lack of experience; the occasional refusal of the government to accept the necessity of their work (one inter-war Secretary of State, Henry Stimson, later declared that ‘Gentlemen do not read each other’s mail’); and an intense rivalry between US Army and US Navy codebreakers. It was not until Rowlett’s breaking of Purple, at a time when all the British machine cipher experts were concentrating their energies on the German Enigma machine, that the American codebreaking operation really came into its own.
None of this is to deny the dominant role played by the Americans in the interception of Japanese messages. At the start of the war, the British were forced to throw all their efforts into breaking the German ciphers. They had neither the resources nor the incentive to pay as much attention to Japanese codebreaking as it undoubtedly deserved. The main Royal Navy codebreaking establishment in the Far East had been forced by the Japanese threat to move first from Hong Kong to Singapore, then to Colombo and swiftly on to Mombasa, where its very remoteness from the battle crippled its ability to receive the Japanese radio messages on which the codebreakers depended. The Americans, by contrast, had immense resources both in terms of manpower and the mechanical tabulating machines that were indispensable to the operations to break the Japanese codes. The US Navy station at Pearl Harbor in particular was second to none in its efficiency and capability.
The British understandably assumed that since they were willing to provide the Americans with all the intelligence they gained from breaking the Enigma ciphers, the Americans would do the same when it came to material gathered by breaking the Japanese codes. The US Army codebreakers proved as helpful during the war in the Far East as they had with their provision of the Purple machine. Sadly, the same cannot be said of some of the administrative officers controlling their naval counterparts.
The refusal of certain sections of the US Navy to share intelligence with the British seriously hampered operations in eastern waters and led the Admiralty to suggest that the fledgling exchange agreement on codebreaking with the Americans should be scrapped. Given that this was to form the basis for the UKUSA Accord which played such a vital role during the Cold War and still links the two countries’ intelligence services, the potentially disastrous effects of the lack of cooperation are not hard to imagine.
The record of the US Navy on cooperation, not just with the British but with their own Army, was not merely lamentable, it was shameful. But it was not the only problem faced by the codebreakers. The very nature of the Far East War, spread as it was over many thousands of miles, made communication between the main codebreaking centres extremely difficult. If Bletchley Park and its US counterparts had problems exchanging information with the various outstations that stretched from East Africa to the West Coast of America, the stations themselves found it almost impossible to co-ordinate their own operations during the early years of the war.
Yet while the codebreakers were only rarely to enjoy the same influence they exerted on the war in Europe and North Africa, their achievements were many. The existing literature credits this almost entirely to the US codebreakers. In fact, with the exception of Purple, only one of the key codes was broken by an American alone and that in Australia. It was British and Australian codebreakers who led the way in breaking the majority of the Emperor’s Codes. Here for the first time is their story.
1
SINGAPORE, DECEMBER 1941
The old Cathay Cinema opposite Fort Canning military base in Singapore was packed for the matinée showing of the latest Rex Harrison film, a screen version of George Bernard Shaw’s play MajorBarbara. For weeks the talk among the city’s expatriate community had been of the threatened war with Japan. But any suggestion that the Japanese might manage to invade Malaya or, heaven forbid, even succeed in capturing the ‘impregnable fortress’ of Singapore was ridiculed by the authorities.
Air Chief Marshal Sir Robert Brooke-Popham, Commander-in-Chief Far East, had told a press conference only two days earlier that there was nothing to worry about. ‘There are clear signs that Japan does not know which way to turn,’ he said. ‘Tojo is scratching his head. There are no signs that Japan is going to attack anyone.’
There had in fact been some very clear signs, all of them pointing to a conclusion directly opposite to that expressed by Brooke-Popham. For the past month, a wireless intercept station at Kranji on the north of Singapore island, an offshoot of the British codebreaking organization based at Bletchley Park, had been picking up radio signals indicating the movement south of a large Japanese armada which was now crossing the Gulf of Siam towards the north-east coast of Malaya.
The intercept operators at the Kranji listening post included a batch of Wrens, four of whom had ‘gone ashore’ – naval parlance for leaving the base – to see MajorBarbara. ‘In the middle of the showing, the film suddenly stopped running and a big sign came up on the screen in two-foot-high letters,’ one of the Wrens recalled. ‘It read: “All British service personnel to report back to barracks immediately”.’ The cinema emptied quickly. But few of those leaving were particularly worried. It was just another security scare. Brooke-Popham had set the popular mood. The Japs were hopeless. There was no chance of them winning anything.
John Burrows, an Intelligence Corps sergeant on Brooke-Popham’s staff, had just arrived in the colony and found the complacency impossible to believe.
It was Cloud Cuckoo Land and to someone like myself who had come from Britain it was unbelievable. There were some who had their doubts, but the planter society as a whole was very comfortable. They had always been able to depend on the British to defend them and they totally underestimated the Japanese military threat. All the able generals were collected in the Middle East at this time and it was the duds who were shipped out to the Far East, some of them with no understanding of reality at all. There were one or two staff officers who were the exception but they hadn’t any power to do anything about it.
The Wrens’ bosses at the Far East Combined Bureau, the British joint service codebreaking and intelligence centre, were among those who were not underestimating the Japs. For the past two months, the airwaves had been full of Japanese radio transmissions and the codebreakers had identified every ship in the Japanese armada. They had also deciphered a message from the Japanese Ambassador in Bangkok to Tokyo revealing that the ships were to land an invasion force at Kota Bharu in north-eastern Malaya. But the British commanders were dismissive of their ‘defeatist’ warnings. The British officer class was reluctant to believe that the good life was about to come to an end.
Until now life in Singapore had been very relaxed, even for the ordinary servicemen and women. The Wrens were in specially built wooden quarters, two sharing a ‘cabin’, each with the luxury of an ensuite bathroom; some even had a cabin to themselves. All the British service personnel had locally employed servants, recalled Lance-Corporal Geoff Day, one of a number of British Army intercept operators working alongside the Royal Navy, WRNS and RAF personnel at Kranji:
*
Our life was one of relative luxury. We had native Malay boys to wait on us hand and foot, make our beds, do our washing and serve us excellent meals. We slept in dormitories built on stilts because of the heavy seasonal rains, and our beds were provided with mosquito nets which were attached to copper wires stretching from one end of the building to the other. During electrical storms lightning would run along the wires, frightening but harmless.
The work could be tiring, often requiring long periods of intense concentration, said Day.
During our evenings off we played contract bridge or we would go into Singapore City to see the movies, to service clubs, of which there were many, or to the three amusement parks: New World, Great World and Happy World. Some of us attended recitals at the Gramophone and Music Society. The city was a very smelly place, particularly near the water. The street stalls selling all kinds of Chinese and Malay food added to the aroma – or should I say stench. Washing was hung on the lines between buildings, across streets. But the young Eurasian girls were truly beautiful. On one occasion some friends and I ventured across the causeway to the north to Johore Bharu to visit a brothel, but drank too much and left without sampling the goods.
Single British women were at a premium in Singapore and some of the Wrens soon found boyfriends. Lillie Gadd fell in love with her instructor at Kranji. ‘Archie was in the Navy,’ she said. ‘We were learning the job alongside the naval operators who had been there for a while. We had to double bank, sit by the side of the operator who was training us, and Archie was watching over me to make sure I did the job right. So we saw each other day and night. We used to go “ashore” together to the pictures or to do a bit of shopping. Archie and I did all our courting in Singapore. We had quite a good time. We always say it was the best time of our lives.’
But things were about to change. The day after the servicemen and women were called out of the Cathay Cinema, Geoff Day went on the ‘middle watch’ at the Kranji intercept site. ‘Since we were on a naval wireless station, we observed navy watches and middle watch meant you were on duty from midnight until a minute past four, when you were relieved.’
John Burrows had already begun the night shift as Duty Intelligence Reporter at GHQ Far East in the Selatar naval base, seven miles east of Kranji. ‘I was working in what was more or less a Nissen hut collating intelligence from all sources, heading up the intelligence support for the Commander-in-Chief.’ Shortly after one o’clock in the morning, Japanese troops began landing at Kota Bharu. It was some time before the first report came in by telephone, Burrows said. ‘I remember one of my superior officers telling me at the time that there was only one telephone line from Kota Bharu to Singapore. That may not actually be true but as an indication of the unpreparedness it is quite vivid.’
At twenty-five minutes past three, the wireless operators at the intercept site were ordered to black out their windows in preparation for a raid by bombers flying in from Saigon. ‘At three forty-one, the sirens went off,’ Geoff Day noted in his diary. ‘At ten past four we were sent “on post” which was considered safer than the accommodation and setroom buildings. At four forty-five, the all-clear sounded. Then, two minutes later, there was another warning siren and the final all-clear went at five fifteen.’
The military bases had been alerted by Fighter Control Operations Room. But the civil Air Raid Precautions Unit was unmanned and no-one could be contacted to sound the sirens. As a result the lights stayed on in Singapore, guiding the Japanese bombers into the skies above the city. ‘I remember sitting there and seeing Japanese aircraft flying overhead and dropping bombs on parts of Singapore which was still brilliantly lit up,’ John Burrows said. ‘You would not believe it but that was how unprepared Singapore was.’
As the Japanese pushed rapidly down the Malay Peninsula, meeting little opposition from the retreating Allied troops, the intercept operators were warned that they were to be evacuated to Colombo with the Far East Combined Bureau’s codebreaking section. Realizing they might never see their boyfriends again, three of the Wrens decided to get married.
Hettie Marshall and her fiancé John Cox, a major in the Indian Army, were married in St Andrew’s Cathedral on 30 December 1941. ‘We were engaged when the Japanese attacked,’ Hettie recalled. ‘At the time, everyone was escaping. The Indians were dashing back off to India. So we just decided to hasten it on. John’s colonel threw a party for him and we had it with a marquee in the gardens of the brigadier’s house.’
A day later, Lillie Gadd married Archie Feeney, also in St Andrew’s Cathedral.
The fighting was coming, we might get separated, anything might happen, so make the best of it while you can, we thought. I had to keep my wedding a secret because in the Navy if a Wren married a sailor they split you up straight away. Archie and I went ashore on the same coach. There was one of the male operators to give me away, the best man and a few of the girls from my watch. I’d had a blue chiffon dress made up in Singapore for my wedding but because the war had begun I had to wear uniform.
We came out to bells but you weren’t allowed to take photographs. Then we just went across the road into the café. We had a bit of a celebration back at the camp with some of the girls but it had to be kept secret. The men slept in a different part of the camp, of course, so we would have to spend our nights apart. But we didn’t that night. We spent our wedding night in my cabin.
On New Year’s Day Rene Skipp married her fiancé, John Watson, a Royal Navy chief petty officer from another unit. ‘It was very much a last-minute affair,’ she recalled. ‘There was no wedding as such. We were married in the registry office and the only other people there were the witnesses.’
Four days later, Lillie and Archie Feeney were evacuated to Colombo with the bulk of the codebreakers and intercept operators. Hettie Cox and Rene Watson were forced to leave their husbands behind. Geoff Day was one of a small party of intercept operators who stayed in Singapore to continue monitoring the Japanese radio messages.
When Singapore finally fell on 15 February 1942, many thousands of Allied servicemen would be captured, spending the rest of the war amid the horrors of Japanese prisoner-of-war camps. But by then John Cox had already been safely evacuated to Java, as had Geoff Day, while John Watson had sailed for Colombo. John Burrows had also escaped, having been recalled to England to work at Bletchley Park. But not before being asked to brief the generals on the complacency that led to the fall of Singapore and on how the codebreakers’ warnings had been ignored.
2
BORROWING THE CABLES
The British had been busy intercepting the diplomatic communications of their enemies, and on occasion their friends, since 1324 when King Edward II ordered that ‘all letters coming from or going to parts beyond the seas be seized’. After a brief period, during the second half of the nineteenth century, when Victorian morality and Foreign Office penny-pinching led to Britain’s codebreakers being declared redundant, the onset of the First World War brought them more work than they might previously have imagined possible.
The British Army was the first organization to realize the potential intelligence to be garnered from ‘censoring’ the German diplomatic communications sent on the cables of the international telegraph companies. The War Office set up a special section, MI1b, inside military intelligence, recruiting a number of eminent academics, a mixture of classicists and Egyptologists, to break the German codes. Shortly afterwards, the Royal Navy followed suit on the orders of Winston Churchill, then First Lord of the Admiralty.
The army and navy codebreakers had little time for each other during the war, competing rather than co-operating in their own petty turf war. Following the Armistice, the moral imperative for ‘censoring’ the private communications of other countries’ ambassadors and the strong desire within the Treasury for a ‘peace dividend’ put their role under renewed threat. But so successful had they been that every other government department was clamouring for more.
The army and navy codebreaking organizations were combined into a single civilian operation of just twenty-five people based in London’s Berkeley Square and known as the Government Code and Cipher School. ‘It was a very small organization for the Treasury had, throughout the negotiations, been insistent on cutting down the expense,’ recalled William ‘Nobby’ Clarke, one of the old Room 40 codebreakers.
With the Foreign Office reluctant to fund its operations, GC&CS was placed under the control of Admiral Hugh ‘Quex’ Sinclair, Director of Naval Intelligence, who moved its offices to Watergate House on the Strand.
But when the lease on Watergate House ran out, it was transferred to a new headquarters at Queen’s Gate in London’s fashionable Kensington district where day-to-day operations were run by Alistair Denniston, a former Royal Navy education officer who had been in charge of codebreaking in Room 40. ‘The public function was “to advise as to the security of codes and ciphers used by all government departments and to assist in their provision”,’ he recalled. ‘The secret directive was “to study the methods of cipher communications used by foreign powers”.’
The War Office’s decision to close its censorship department caused major problems for Denniston and his codebreakers. Britain was a central point on the international cable network and messages from all over the world passed through London on their way to their ultimate destinations, so the censorship system had produced large amounts of intelligence on the activities of a wide variety of foreign governments.
‘Temporary unofficial arrangements were made with the moribund censors which provided the cable traffic for some further months,’ Denniston recalled. However, this was not enough to keep the supply of cables going indefinitely. Tapping the cables themselves was deemed to be too expensive. But although unwilling to fund the operations, the Foreign Office insisted that there was no question of not obtaining the information they carried.
‘The deciphered telegrams of foreign governments are without doubt the most valuable source of our secret information respecting their policy and actions,’ said Lord Curzon, the Foreign Secretary. ‘They have proved the most accurate and, withal, intrinsically the cheapest means of obtaining secret information that exist.’
The easiest solution was for the codebreakers to take over the role of ‘censorship’. So the cable companies were approached to hand over all their traffic to GC&CS, which would copy it before returning it to them. This presented no problem with one of the companies, Cable and Wireless, which was British-owned. But the other two, the Commercial Cable Postal Telegraph Company and Western Union, were American. They would need some persuasion before they handed any cables over to the British.
The Official Secrets Act already gave the Government the right to scrutinize cable traffic for purposes other than censorship, Denniston recalled. ‘A clause was inserted authorizing a secretary of state to issue a warrant to cable companies operating in the UK requiring these companies to hand over all traffic passing over their systems in the UK within ten days of receipt.’ The maximum punishment for refusing to hand over the cables was only a £100 fine or a three-month prison sentence so the Government still depended heavily on the goodwill of the cable companies. The last thing it wanted was for the procedure to become public knowledge. ‘Secrecy is essential,’ Lord Curzon told his cabinet colleagues. ‘It must be remembered that the companies who still supply the original messages to us regard the intervention of the Government with much suspicion and some ill-will. It is important to leave this part of our activity to the deepest possible obscurity.’
It was not to be. The British practice of ‘borrowing’ the cables became the focus of an investigation by the US Senate. Western Union’s president, Newcomb Carlton, was forced to describe how his company connived with the intelligence service of a foreign power, but defended himself by pointing out that most of the telegrams were encoded. ‘Messages in their original form – ninety per cent of them are in code – are taken to, I think, the British Naval Intelligence Bureau,’ he said. ‘They hold them not more than a few hours and then return them. They do not hold them long enough for anything like deciphering.’
This somewhat weak defence was ridiculed by the chairman of the investigation, who pointed out that it only took a few seconds to make a copy which could then be decoded at leisure. Nevertheless, the cables continued to flow into the Government Code and Cipher School where they were sorted in a department run by Henry Maine, one of the First World War codebreakers. Despite the implicit coercion, the relationship with the cable companies was handled in a thoroughly gentlemanly, and typically English, fashion. ‘It was our aim to make this procedure work smoothly with the companies,’ Denniston said. ‘It was undoubtedly a nuisance for them to have to send all their traffic in sacks to an outside department and I have always considered that the credit for smooth working and no questioning should go to Maine.’ The cablegrams were sorted and copied by a small group of workers borrowed from the Post Office, he added. ‘Our aim was to inconvenience the companies as little as possible and throughout we tried to let them have their traffic back within twenty-four hours, though many million telegrams must have passed through their hands.’
The telegrams handed over by the cable companies were to provide the mainstay of the codebreakers’ work. Although GC&CS; came under the control of the Admiralty, the interest in naval intercepts had ended with the war. The codebreakers’ main work was deciphering diplomatic messages, Nobby Clarke said. ‘To give some idea of the change: in the early days of 1920, the strongest section of the GC&CS was the United States section.’ The other most important priorities were the diplomatic ciphers of France, the Soviet Union and Japan, a former wartime ally but now increasingly regarded as a major threat to Britain’s colonies in the Far East.
Fortunately, Maine was not content with obtaining the cables passing through London; he also made arrangements with Cable and Wireless to receive those available at other points on the international network, in particular Malta, a move that was to prove crucial to the interception of Japanese diplomatic telegrams. The Cable and Wireless repeater station on the island handled all the traffic between Europe and the Far East, including the telegrams from Tokyo to the Japanese embassies in London, Paris, Rome and Berlin. On Maine’s instructions, Cable and Wireless had copies of all the telegrams sent to London for ‘accountancy purposes’.
The GC&CS Japanese expert was Ernest Hobart-Hampden, a former senior official at the British Embassy in Tokyo and co-editor of the leading English–Japanese dictionary. So easy were the Japanese codes that ‘the cryptographic task was for the first ten years almost non-existent’, Denniston said. ‘For the language, which was the main difficulty, we were lucky enough to have recruited Hobart-Hampden, just retired from thirty years’ service in the East. For a long time, he was virtually alone. But with his knowledge of the habits of the Japanese, he soon acquired an uncanny skill in never missing the important.’
The first big test of Hobart-Hampden’s uncanny skill came with the 1921 Washington Conference of the nine major powers. The Japanese had emerged from the First World War as the third largest naval power behind Britain and America and were determined to expand their influence in the Far East, particularly in China. Britain and America were determined to curb these ambitions and planned to use the conference to limit the ratio of their own naval ships to ten for every six Japanese vessels.
Both GC&CS and its US equivalent, the Black Chamber, were able to monitor the Japanese attitude to the Washington Conference, giving them a valuable advantage in the negotiations. During the first few weeks of the conference, the Japanese stuck out for a much tougher deal than the 10:6 ratio wanted by the British and Americans. But on 28 November 1921, with the talks reaching their conclusion, the codebreakers intercepted a message from Tokyo to the Japanese delegation. ‘We think it necessary to avoid any conflict with England or the United States,’ it said. ‘If it becomes absolutely necessary, make it clear that this is our intention in agreeing a ratio of 10:6.’ From that point on, the US and British delegations could hold out for the required ratio safe in the knowledge that the Japanese would eventually agree to it.
Herbert Yardley, the head of the US Black Chamber, later published his memoirs, revealing the success of the American codebreakers covering the conference. But the full scale of the information provided by GC&CS; to the British negotiators, which no doubt included intelligence on the position of the Americans as well as that of the Japanese, is still shrouded in secrecy. ‘No-one will ever tell how much accurate and reliable information was made available to our Foreign Office and service departments during those critical years,’ said Denniston. However, he made it clear that Hobart-Hampden’s contribution was critical. ‘Throughout the period down to 1931, no big conference was held in Washington, London or Geneva in which he did not contribute all the views of the Japanese Government and of their too verbose representatives.’
Although virtually all the messages decrypted by GC&CS; were diplomatic, the Foreign Office still appeared happy to allow the Admiralty to continue to control, and perhaps more importantly to fund, the cost of the codebreaking operations, Clarke recalled.
Things went on in a fairly peaceful way until in March 1922 a curious thing happened. Lord Curzon, at that time Foreign Secretary, had an interview with the French Ambassador in London at which he expressed certain views which did not coincide with the views of his colleagues in the Cabinet; at any rate he impressed on the Ambassador the desirability of keeping them secret.
The Ambassador duly reported the interview to the French Foreign Minister, as was his duty. His dispatch went by wireless, was intercepted by our stations and decoded by us. The decode was duly circulated to the usual recipients, the War Office and others. Curzon was furious. His reaction was immediate and he at once persuaded the First Lord that he might just as well hand GC&CS to the control of the Foreign Office, the very department which had refused to have anything to do with it three years before. The change made little difference, except that our new heads had only a vague idea of our possibilities.
A year later, Admiral Sinclair was made ‘Chief’ of Britain’s Secret Service, which was also controlled by the Foreign Office, and was again placed in charge of GC&CS. Sinclair was a man of considerable means who was fond of fast cars and even faster living. But the Treasury’s demands for a post-war peace dividend had forced him to run MI6 on a shoestring, recruiting former army officers because they already had pensions and paying them Christmas bonuses out of his own pocket. ‘I liked him very much,’ said Clarke. ‘He was an extremely able and shrewd man, and during the next seventeen years I got to like him more and more. He trusted his subordinates and would take one’s word as to the advisability of a certain course and give one the utmost help.’
With Sinclair’s support, Clarke spent a great deal of time trying to persuade the Royal Navy that more attention should be given to intercepting foreign naval messages. ‘There was no naval cryptography done and the Admiralty wireless stations were all engaged in diplomatic traffic. I tried to get the Fleet interested in interception as I thought it would be useful one day. A large quantity of useful material could be got if sufficient interest in the work could be aroused.’ Clarke gave lectures on the exploits of Room 40 and eventually managed to build up interest in codebreaking with a number of enthusiastic officers working in their spare time to produce a steady stream of French and Russian naval messages.
‘A greater problem presented itself in respect of Japanese, which it was recognized quite early on was of great importance,’ said Clarke. ‘The first difficulty was that the Japanese Morse code consists of about twice as many signs as the English.’
The advent of the telegraph had brought problems for the Japanese, whose written language was based on pictorial characters or ideographs, called kanji, and around seventy phonetic symbols called kana. The sound of words depicted by kanji can be represented using kana. However, this can lead to ambiguity since the Japanese language has a large number of different words which, while having distinctive written forms, sound the same (much like principal and principle in English). So a system of transliteration known as romaji developed which allowed the kana syllables to be spelled out in Roman letters. The Japanese created their own Morse code which contained all the kana syllables plus the romaji letters and was totally different from the standard international system that the Royal Naval wireless intercept operators were used to taking, Clarke recalled.
Ordinary wireless operators were faced with a number of Morse signs which were new to them and early intercepts from HM ships in Eastern waters (which of course took a long time to reach London) were quite unintelligible. Operators had to be trained to take this down in some form or other and then the messages so received had to be transformed so as to represent the actual Japanese messages. The initial stages were very difficult and many an obstacle had to be surmounted, but directly it had been proved that progress was possible the authorities at last recognized the importance of our work.
Clarke was appointed to head a small naval section within GC&CS. The Admiralty sent the best officer from its most recent three-year Japanese-language course, Paymaster Lieutenant-Commander Harry Shaw, to assist Hobart-Hampden with the telegrams sent by Japanese naval attachés, but there was a desperate shortage of Japanese interpreters in the navy and it was difficult to find suitably qualified officers to work on other naval messages.
The Royal Navy set about increasing the incentive for officers to learn Japanese, but with the course requiring a minimum of two years to be spent in Tokyo, this was bound to be a slow task. ‘Owing to the extreme difficulty of the language, we have very few officers who could be relied on to read an intercepted “en clair” Japanese message,’ the Naval Intelligence Department complained. ‘This state of affairs might be disastrous in the event of a war in the Far East.’
Clarke discussed the problem with Harold Parlett, co-author with Hobart-Hampden of the leading English– Japanese dictionary and the latter’s replacement as Japanese Counsellor at the Tokyo Embassy. Parlett, who was the head of the board which tested the Royal Navy interpreters, told him of a brilliant young Australian linguist who had received even higher marks than Shaw and whose knowledge of Japanese was ‘on a higher plane of practical utility than is usually obtainable in two years’.
Paymaster Lieutenant Eric Nave had joined the Royal Australian Navy in 1917 at the age of 18 and hired a private tutor to teach him Japanese after hearing that proficiency in the language would entitle him to an extra five shillings a day. He did so well in the official language test that, in February 1921, he was sent to Japan to study as an interpreter. After two years’ intensive study, Nave’s language skills were tested at the British Embassy. ‘My examiner was Sir Harold Parlett, an accomplished scholar and to me a respected figure,’ Nave said. ‘He was after all the Japanese Counsellor, the senior post at the embassy for one with language knowledge. He came from the Consular Corps, a small band, all specialists in Japanese who spent their service in Japan, Korea, or Manila, with an occasional stint at the Foreign Office in London. I was quite delighted when given my examination result, a pass with over ninety per cent, the highest ever achieved by any service language officer.’
On his return to Australia, Nave was posted to HMAS Sydney, the RAN’s flagship, where he began setting up an operation to intercept Japanese messages. ‘I would suggest that all ships in the Fleet be instructed to intercept as many messages in Japanese as possible, these messages to be sent to me for decoding,’ he said in a memo to his superiors in October 1924. ‘Telegraphic messages in Japanese are more difficult than in English, as the Japanese ideographs are not easily abbreviated. After reading plain-language messages, I propose attempting to decode ordinary Japanese economic code messages, with a view to later breaking down the ciphers.’
It is not clear if Clarke was aware that Nave was already working on intercepted Japanese messages or was simply going on the recommendation of Parlett and Shaw, but he seems to have decided that the Australian was just the man he needed to help him break the Japanese naval codes. Denniston saw the fact that Nave was Australian as an insurmountable difficulty, Clarke recalled: ‘So I short-circuited him and went to Admiral Sinclair, who listened patiently and went off straight to the Admiralty whence I was rung up two hours later to ask what was the exact type of officer I wanted.’
The RAN received a message from the Admiralty asking them for the loan of Nave’s services.
My appointment was to be in HMS Hawkins, the flagship of the Commander-in-Chief, China Squadron, to act as a Japanese interpreter. The Naval Board had asked for further information and whether it was for duty on Admiral’s staff. In a few weeks, we were told: ‘Admiralty pressing for appointment of Nave for interpreter’s duties on Commander-in-Chief’s Staff. Naval Board consider Admiralty wishes should be met and propose embarkation in Mishimamaru 26 June.’ The die was cast, but I could have no idea of the effect of this appointment on my career and indeed my whole life.
Nave arrived in Shanghai in July 1925. ‘The admiral on whose staff I was to serve was Sir Edwin Sinclair Alexander-Sinclair, a dour character from the north of Scotland. He had received advice from Admiralty, London, that “Lieutenant Nave is not to be employed in the Admiral’s Office nor on ship duties, details will be forwarded by safe hand bag.” This was intriguing and when they arrived the Admiralty instructions were noteworthy for their complete lack of information and directions.’ The orders did in fact lay out precisely what the Admiralty wanted, albeit with a firm instruction that there were to be no additional funds to pay for it.
Their Lordships have had under review the question of interception of foreign wireless telegraphy messages – a subject to which they attach the greatest importance. The extent to which this method of obtaining intelligence can be utilized in war largely depends on a plentiful supply of naval cipher messages in peacetime. Owing to the necessity of economy, it is not possible to provide any special organization for this purpose on the China Station. The material must, therefore, be provided by HM ships under your command. To enable this to be done, ships should be specially detailed for the duty when opportunities arise. Up to the present, only a small number of naval cipher messages have been received and a great many more are required.
Their Lordships are of the opinion that the difficulty of passing intercepts from such places as Shanghai to Singapore rules out the latter as a deciphering centre. Nor does Hong Kong appear to be suitable for this purpose, for owing to its distance from Japan, it would have to be supplied from other areas and its liability to attack is an additional objection. The use of a ship as a combined intercepting and deciphering centre appears to offer the best solution.
The orders included a stern security warning: ‘Their Lordships attach great importance to secrecy in this matter, for although the Japanese may be doing the same thing, they may not credit us with an equal degree of intelligence.’ In order to restrict the number of people who knew about the interception of foreign messages it would henceforth be known as ‘Procedure Y’ and all reports or correspondence on the subject were to be addressed direct to the Director of Naval Intelligence.
There was, however, no indication in the Admiralty orders as to how the messages were to be intercepted or the codes broken. Nave said, ‘I had to organize this interception myself. Success or failure depended on me alone.’
He was allocated a wireless-trained petty officer, Gordon Flintham, to help organize the interception operations and together they began to unravel the mysteries of the Japanese Morse system. ‘When we started we could not even read Japanese Morse,’ said Nave. Eventually they intercepted a practice message in which the operator had run through the entire Japanese Morse code symbol by symbol. ‘This was our start. Instructions could now be issued to all ships on the China Station to intercept Japanese naval traffic and forward the messages to the flagship.’
Nave used the intercepted Japanese naval messages to build a picture of the make-up of the Japanese fleets and began attempting to break the tasogare, the basic naval reporting code used by the Japanese to announce the sailings of individual ships.
We started with watch on Tokyo radio and found it changed from the Commercial Call Sign ‘JJC’ to the Naval Service Call Sign ‘AB’ at hourly intervals. [Station AB was the main Tokyo naval control which was communicating with all the major Japanese naval bases.] This immediately led to identifying the main naval bases of Yokosuka, Kure and Sasebo and to the lesser bases under their umbrella. Yokosuka repeated signals at times for Chichijima, Kure for Maizuru, Sasebo for Bako, etc. The addressees of messages were spelled out at the beginning. This could be called a self-evident code with ‘da’ for daijin – the Minister of Marine; ‘shichi’ for shireichookan, or Commander-in-Chief. Ships themselves were abbreviated and could readily be identified. This step led me to identifying many call signs of commands, battleships and other vessels. Moreover, it had further value in showing a great deal of the naval organization and the extent of authority of the main naval bases. I had excellent co-operation from wireless operators, particularly those in gunboats in isolated ports. The volume of traffic kept me working at my desk six to seven hours each day, often Sundays as well, extracting and collating a vast amount of information. I certainly had no shortage of material for my regular reports to London.
All the information Nave managed to produce, together with any messages he was unable to break, were to be sent back by bag to the Admiralty in London which passed them straight on to the codebreakers. ‘From then onwards,’ Denniston wrote, ‘there was a flow of traffic by bag to London where the various codes were segregated and broken as far as possible and a return flow of officers with skeleton books to carry on the work locally.’
When the messages began arriving back in the naval section, Harry Shaw was moved across to take charge of the London end of breaking the Japanese naval reporting code. ‘A system of rotation arose,’ Denniston recalled. ‘Officers still on the active list came to us for two years and then joined the China Squadron in a ship where there were facilities for local interception. Thus a first start was made on Japanese naval traffic.’
The British codebreakers were assisted by the Japanese belief that their language was impregnable to others. Communications security was lax and many messages were sent in clear rather than encoded. When the receiving station had trouble deciphering a message, the other operator often provided assistance. Even where the Japanese stuck strictly to the codes, their insistence on using flowery preambles was a great help to the codebreakers. Messages to a superior tended to begin with the predictable phrase: ‘I have the honour to report to your excellency that’, providing Nave with an easy ‘crib’ of what was likely to be in the first part of the message and a way into the code itself.
When the Japanese Emperor Yoshihito died at the end of 1926, the official report of his death and the succession speech of his son Hirohito were relayed to every Japanese diplomatic, naval and military outpost around the world. Nave knew that the Japanese love of ceremony and obsession with predictable courtesies would ensure that every message was exactly the same. It was a simple task to follow it through the Japanese codes, breaking each in turn.
The codebreakers in London concentrated on the standard cryptographic technique of examining the statistical peculiarity of the Japanese language to work out the probability of each individual character appearing. The first step in breaking any cipher is to try to find features which correspond to the original plain text. Whereas codes substitute groups of letters or figures for words, phrases or even complete concepts, ciphers replace every individual letter of every word. They therefore tend to reflect the characteristics of the language in which the original text was written. This provides the codebreaker with a relatively easy entry point. For example, the most common letters in the English language are E, T, A, O and N. If a reasonable amount, or ‘depth’, of English text enciphered in the same simple cipher were studied for ‘letter frequency’, the letter that came up most often would represent E. The second most common letter would be T and so on. Writing out the letters recovered in this fashion will reveal obvious words with letters missing, allowing the codebreaker to fill in the gaps and recover those letters as well. They can in turn be filled in, producing other obvious words and so the process goes on until the whole message can be read.
Another basic weapon used by the codebreaker, ‘contact analysis’, takes this principle a step further. Some letters will appear frequently alongside each other. The most obvious example in the English language is TH, as in ‘the’ or ‘that’. So, by combining these two weapons, the codebreaker could make a reasonable guess that, where a single letter appeared repeatedly after the T which he had already recovered from letter frequency, the unknown letter was probably H, particularly if the next letter had already been recovered as E. In that case, he might conclude that the letter after the E was probably the start of a new word and so the process of building up the message would go on.
The Japanese diplomatic messages were sent using romaji, where the syllables were spelled out using the letters of the Roman alphabet, and were particularly susceptible to contact analysis, one codebreaker recalled.
The orthographic structure of the Romanized Japanese used by the Japanese Foreign Office in its telegraphic communications worked to our advantage. In this form of Japanese certain limitations applied to the letter Y. It was [nearly] always followed by A, and almost never by E or I. Pairs of vowels frequently occurred, and the most common were the combinations OO, UU, AI and EI in about that order of frequency. YUU and YOO often occurred, preceded by a consonant, in combinations such as RYOO, RYUU, KYOO and KYUU. It was our hope that we could use these characteristics of the Japanese language to make accurate assumptions for plain text.
Nave made swift progress with the Japanese naval codes. ‘Using our own reporting messages as background information, I was able to decode all Japanese naval reporting code traffic towards the end of my first year,’ he said. He also made considerable inroads into the more complicated General Operational Code used for most major messages, which was sent in groups of nine letters.
He soon built up a complete picture of the Imperial Japanese Navy, with every ship and its base recorded and every call sign and frequency they used for their radio messages carefully logged. As a result, the British were able to keep track of Japanese naval movements and managed to read a considerable proportion of the messages passing between the Japanese ships and their bases.
At the end of each month, Nave sent a summary of the month’s work back to London, adding the newly broken parts to each code,
