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Telephone: 

EXECUTIVE 3-1940 

MOP.3993. 

REFs~~r*61BB 

BRITISH JOINT SERVICES MISS!~ 

MAm NA.VY BUILDING 

WASHINGTON 25, D.C. 

18th May, 1954. 

MEMORANDUM FOR THE CHAIRMAN. UNITED STA'l'ES CCMMYNICATIONS 

!N:rELLIGQCE BQARD. 

The Chairman or the Iondon Signal Intelligence Board 

has asked me to pass the following message to you:-

n M;y attention has been drawn by a number of authorities 

to the exposures in Chapter 3 or Admiral Theobald's recently 

published book entitled n The Final Secret of Pearl Harbor", 

the text of which is also published in the •u.s. News and 

World Report• dated 2nd April. 

While most or the book reveals nothing from the Sigint 

point of view beyond what has already appeared in the report 

of the Congressional Enquiry, there is one statement that, so 

far as we are aware, has not been published bef'ore, namely, 

that one of the batch of' six purple machines manufactured in 

U.S. was given to U.K. before Pearl Harbor. Thus cryptanalytic co-operation between the U.S. and the U.K. before 

our two countries were official allies is admitted. 

I would be gratef'ul for your views and comments on 

this disclosure•. 

PL 86-36/50 USC 3605 

(signed) 

Enclosure l with USCIB 13.5/69 dtd 25 May 54. 

Declassified and approved for release by NSA on 05-07-2014 pursuant to E. 0. 1352B 

SECRET 
"" - It' 

-~81889 

UNITED STATES CCJ.OOJNICATIONS INTELLIGENCE BOARD 

WASHINGTON 25, D. C. 

OFFICE CJF THE CHAIRMAN 

DRAFT/25 May 1954 

MEMORANDUM FQR THE CHAIRMAN. I.SIB: 

Subject: Revelation of US-UK Cryptanalytic Cooperation Prior to 

Pearl Harbor Attack. PL 86-36/50 USC 3605 

l. The information set QbE~low is in response to your message delivered by hand of Colonel 8.nd requesting our views and comment 

on certain aspects or RADM Theo 1s recently published book entitled 

•The Final Secret ot Pearl Harbor." 

. 2. While USCIB deplores the publication in question it has not been 

able to find any security violation therein nor any basis for action 

against either author or publisher • 

.3. With specific reference to the point of revelation of US-UK 

cryptanalytic cooperation before our two countries were official allies 

the .following extract from page 85 of Part .34 o.f the Report of the Pearl 

Harbor Investigation, 79th Congress, 1st Session forms a part of the 

public record in the U.S.: 

•PART .34 

·PROCEEDINGS OF CLARKE INVESTIGATION 

PART II 

FINDINGS 

Testimony- of William F. Friedman 

• ••• after we solved the Purple system, the technical data 

necessary to operate the system and a machine constructed by ourselves 

were turned over to the British so they were in a position to process 

Purple messages also. • • 

•GENERAL CLARKE: On approximately what date did we give the Purple 

Machine to the British? 

•MR. FRIEDMAN: I recall that very clearly. A joint U.S. Navyu.s. Army cryptanalytic mission consisting of four o.fficers, two :tram 

each service, went to London for the purpose of establishing technical 

cooperation with the British cryptanalytic service. It was at that time 

the Army f.'urnished a Purple Machine and the technical data to the British." 

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Enclosure 2 with USCIB l.3.5/69 dtd 25 May 54. 

SECR-ET 
Subject: 

~68188 e 

Revelation of US-UK Cryptanalytic Cooperation Prior to 

Pearl Harbor Attack. 

-------------------------------------- 4. In the course of investigating this incident it has been learned 

RADM Theobald (now retired) was never a recipient of CCMINT and apparently 

used no classified sources in writing his book ..... · 'l'b."ese facts are sufficient 

to explain why the manuscript was not submitted for review prior to 

publication. 

5. uscm•s po+!cy with regard to public utterances conta;5ning 

CCMINT information already a matter of public record is to require its 

members to take all feasible administrative action to inaure prior review 

of the material and to discourage by all reasonable, means the repetition 

therein of revelations which are considered to be still of a damaging 

nature •. It is recogni~ed that this does not provide vary effective 

insurance. · 

6. It is hoped that the above will serve to answer your request 

for views and comments on this matter. 

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SECRET 

(DRAFT) 

ALLEN W. DULLJ!5 

Chairman