Speaking of the
'prior to the opening of hostilities
situation', Ronald Lewin, in Ultra Goes To War (1978 Hutchison & Co.
Ltd., London) gets straight to the point, and so will I:-
"And in no field - as intensive inquiries
into Pearl Harbor and its preliminaries have demonstrated - was the American
administration proved to have been more amateur than in its handling of the cryptographic
intelligence which its agencies abundantly supplied."
So let's get a few working definitions
settled before we go on. ULTRA, in the context in which I am using it, was the overall
name that was given to the product of code breaking. We can talk about ULTRA now,
because until 1974 it had remained one of the most protected secrets of WW2 that had never
been allowed into the public domain. In 1974, Group Captain Frederick W. Winterbotham, writing from memory and without access to official papers, released The
Ultra Secret (Harper & Row 1974) and though later authors would criticize it
for being neither encyclopedic or precise, it was the seminal work in the
field. In the US context, MAGIC was the same as ULTRA.
Codebreaking during WW2 was an operation
so compartmentalised, and so enormous, that no single individual could come to grips
with the 'big picture' and what followed Winterbotham were a number of books which
represented partial experiences with vignettes of the 'big picture'.
Purple was
the name which the Americans gave to the Alphabetical Typewriter 97 machine utilized by
the Japanese Foreign Office for encoding and decoding messages. In time it would
come almost synonymous with the product of the codebreaking of the Japanese diplomatic
codes. By 1937 (year 2597 of the Japanese calendar) the Japanese
Foreign Office had acquired a commercial Enigma machine, and after modifying and
improving it, it was adopted by the Imperial Navy for signal security, and then by the
Foreign Office. Indeed, it would be the use of the Type 97 cypher machine by the
Foreign Office which would attract America's premier codebreaker of the time, William
Friedman.
From 1937, Purple
would be Friedman's preoccupation. By 1940, after his relentless effort in mastering
the Purple cypher, he withdrew temporarily to a neuro-psychiatric ward to deal with the
burn-out brought about by the prolonged stress. But by cracking Purple, he ensured that the United States could read the Japanese
Diplomatic traffic.
Whereas the American
government operated through its diplomats, that was not necessarily the case in
Japan, where the real people in power were the armed forces, not the civilian government
and it's Diplomats. The Japanese, in fact , trusted their diplomats somewhat less than
foreign governments trusted theirs, and not every important instruction was carried by
Purple. Indeed, the manner in which
the Japanese played their own diplomats in the negotiations leading towards Pearl Harbor
reminds one of an expert magician - focus the audience's attention on the hand that is not
performing the trick.
In retrospect, it has
appeared to many historians and writers (Van Der Rhoer, Ronald Lewin, James Rusbridger,
Eric Nave, Clark, William Kahn and more recently Bruce Lee) that the access Purple gave the United States to sensitive communications prior to
Pearl Harbor did as much harm as good. The same breakthrough that made it possible
to read Japan's most important and sensitive diplomatic communications - those passing
back and forth between the minister of foreign affairs in Tokyo and the ambassadors in
Washington, London, Berlin, Rome and Moscow - had an intoxicating effect on the American
inner circle given access to the material. Van der Rhoer goes so far as to say that
it did more harm than good.
Operational Orders, those
that directed fleets, invasions, raids and the like, were not transmitted by
Purple. The
Imperial Army and the Navy each had their own operational codes. (If one thinks of
the Japanese Imperial Army and the Japanese Navy as huge corporations
competing against each other for the military budget allocations to finance and sustain
their own war, as opposed to their competitor's war, then one can begin to
comprehend why the Pacific War was fought the way it was, and even why it happened.)
The Japanese Imperial Army's war had already been running for several years in
China, and the Navy was a very minor player in it. In the Pacific, where it was the
Navy which had brought on the war against the Americans, the Japanese Navy's
Operational orders were transmitted in a code named JN-25.
When one gets
into any discussion of codebreaking in the Pacific War by far the big
noise which grabs almost all the public's attention is the story of
Purple. It's
so far ahead in the mind of the US public (at least those of the public who care for
such things) that there's hardly any room for whatever comes second. It's
heroic, it's the success story, and there's nothing an American loves more than a
success story. It's the one which gets the publicity and the spotlight, and what
comes next is 'close, but no cigar'. You have got to do a lot of reading of
a lot of books before you start to question the accepted vision, and the suspicion
that the big story of the Pacific War is actually JN-25 and not
Purple,
comes as a thief in the
night.
When you look more
closely at the texts, you recognize that it's the decryption of JN-25 which brought
on the successes at Coral Sea and Midway, and that it's the reading of JN-25 which got
Yamamoto shot down. Where was
Purple then?
Midway is the first, the classic example
of how cryptoanalysis was used to spring a surprise and achieve decisive results in the
Pacific War, and it was the reading of JN-25, not
Purple that made it so.
Why would there be all
the hoopla around
Purple
and
not around JN-25? The answer is that mixed in with JN-25 there are some very
serious areas of continuing sensitivity, even fifty years after the
cessation of hostilities. And there is no greater sensitivity of
Pacific War cryptography that I know of than the issue of when it was that
JN-25 first began to be read.
This is an issue which
still has some very powerful sectional interest groups protecting their individual
interests. The British, one must never forget, were in the war some years prior to
the US, and they were sufficiently concerned for the safety of their Far East Empire to
have their code-breakers working against Japan from not just from Bletchley Park, but
from Hong Kong, Delhi, Colombo and Singapore. There was a Japanese section at
Bletchley, staffed to a large degree by young men of ability recruited from Cambridge who
had successfully mastered a six month crash course in Japanese. In Ultra Goes To War
(1978 Hutchison & Co. Ltd., London) , author Ronald Lewin comments of them
"the exact function and achievement of this section has never been revealed."
Indications raise the probability that they were reading JN-25 well before the US, and
that they were withholding from the US, then a neutral, the extent of their success
against it.
If the British were
reading JN-25 before the Americans, and that's where the smart money is, and one
follows this line of thought through to it's logical conclusion, then the big question to
be answered is what the British knew of the Japanese plans concerning Pearl Harbor before
it occurred.
The speculation of the
revisionist historians is that Winston Churchill knew that the Japanese Navy was on it's
way to attack Pearl Harbor, and withheld that information from the Americans. Surely
a good move from the British point of view, and perhaps a very good reason why American
historians tend to treat him without the veneration accorded him by the historians
on the other side of the Atlantic.
The issue affects the US
in a far different manner. The issue of when they first were able to read JN-25 raises
three possibilities:
(a) They were
concentrating their limited resources on reading the diplomatic intercepts, and that the
operational orders, being a lesser priority, were being looked at only on an ad hoc
basis. They could only began to concentrate on JN-25 when they discovered the
error, and were given more resources. The reason why there are no decrypts with
decrypt dates prior to 7 December 1941 is that none (or not many) were
decrypted before that date. The surprise at Pearl Harbor was brought about by
negligence - the failure of the United States to recognize the importance of creating a
system for obtaining and interpreting operational and not just diplomatic enemy
intelligence and rendering both understandable to their respective users. There is no
conspiracy.
(b) They were reading
JN-25 prior to Pearl Harbor and through a combination of excessive compartmentalisation, amateurish handling of the 'product' and 'yield', that
actual foreknowledge of the impending raid on Pearl Harbor was lost in the bureaucratic
machinations of the system. The reason why there are no decrypts with decrypt dates prior
to 7 December 1941 is that powerful persons within the USN covered up their
institutional embarrassment from the prying eyes of history, and removed them from the
archives. This being done, the US has prevailed upon the governments of Britain and
Australia to ensure that no materials from their archives are released which are
inconsistent with the official line that JN-25 was first cracked only after 7 December
1941.
(c) The reason why there
are no decrypts with decrypt dates prior to 7 December 1941 is that, in truth, no
one had been able to read them before that date, and that only a major effort spurred on
by the disaster brought about their being cracked.
The variations of these
possibilities is staggering.
One very telling book is
"Deadly Magic" (1978 Charles Scribner's Sons, New York)
by Edward Van Der Rhoer. The author is one of those people who was
compartmentalised, and not graced with a 'need to know' the big picture. But from
what he relates, it appears that he was working in a section that was dealing with the
Japanese Operational (as distinct from diplomatic or Purple) codes. Though he does
not refer to JN-25 anywhere in his book, as if it had been required of him not to mention
it by name, it appears that the compartment within which he worked at OP-20-GZ
was working on JN-25, that is, when it wasn't working on reading and translating the
encyphered Purple traffic. The intercepted traffic from the Japanese Consulate
at Honolulu was considered 'low-level intelligence' and piled up in the In-basket.
Van Der Rhoer relates
that on 6 December 1941, a colleague, Dorothy Edger, had picked out from the In-box a
lengthy intercept that happened to be one of the Japanese Naval Intelligence officer's
messages from the consulate at Honolulu on 3 December 1941. This message
had tweaked her interest, and she had worked on it throughout the afternoon, even after
she was due to go home for the day. It was about a set of signals which was to be
used in sending information about the US fleet in Pearl Harbor.
When (Commander) Kramer
finally appeared later in the afternoon, she spoke to him about it. By her account, he
scanned the text rapidly, just standing there. He handed it back to her without a word.
"What should I do
with it?" Dorothy asked.
"It can wait until
Monday."
Dorothy was not aware
that Kramer had already immersed himself in the first parts of the fourteen-part message
that was coming in over the PURPLE machine. He had seen enough to know that the message
contained a diplomatic note that was obviously Japan's answer to the United States in the
ongoing negotiations. ...
Yet if he had not been
so preoccupied with the fourteen-part message in PURPLE, Kramer would have certainly realized that the signal system
described in Dorothy Edger's message was a visual one meant to be observed by Japanese
submarines standing offshore at Oahu while the radio ads could be picked up by the
submarines or even surface ships not far away from Hawaii.
Kramer's fate, Van
Der Rhoer goes on to relate, was to live under a cloud for years, from where
he would be called on to testify before naval boards of inquiry and congressional
investigations for a number of years, even after the end of the war.
So where is that likely to leave us, on
this Corregidor website? Even prior to the opening of hostilities, the Corregidor unit
had, together with the Singapore unit, commenced the attack and breakdown of
JN25.
