Japan Broke U.S. and British Diplomatic Codes Before Pearl Harbor

[Nicholas Bohm]

At 14:48 08-12-2001 +0000, Ben Meghreblian wrote:
>December 7, 2001
>
>http://www.latimes.com/news/nationworld/world/la-120701codes.story
>
>TOKYO -- Toshihiro Minohara made a startling discovery while digging 
>through the U.S. National Archives in College Park, Md., last summer. While 
>researching secret codes used prior to the attack on Pearl Harbor 60 years 
>ago, the young Japanese American professor stumbled upon a document, 
>declassified by the CIA about five years ago, that proved that Tokyo had 
>succeeded in breaking the U.S. and British diplomatic codes. A few 
>microfilmed documents, showing the Japanese translations of the telegrams, 
>were attached.

It does seem that Axis cipher successes (and in due course some analysis of
their effects) represent a substantial area of unfinished business.

The Enigma histories reveal one or two cases where Enigma breaks revealed
the fact of earlier German breaks into Allied ciphers, but the histories do
not pursue the question of what if any action was taken in the light of
this discovery.  Likewise I read recently that the Churchill/Roosevelt
voice scrambler was broken by the Germans within five or six months of its
first use, with subsequent transcripts supplied to Hitler, but I have seen
no analysis of the impact on the course of the war.

There must be more to come.

Regards

Nicholas

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