REF ID:A61232 

SECRET. 

OEOfloiJ'P 

OP-20-G/ir 

(SC)A6-2/A8 

Serial 0325520 

0 0 p y 

June 20, 1942 

From: 

To: 

SubJect. 

The Commander-in-Chief, United States Fleet 

end Chief ot Naval Operations. The Commander-in-Chief, United States Atlantic Fleet 

The Commander-in-Chief, United States ?acific Fleet 

The Commander, Southwest Pacific Force. 

Control of dissemination eDd use of radio 

intelligence. 

1. The extreme importance of radio intelligence 

as a reliable source of enemy information has been repeatedly ~emonstrated. From no other form of intelligence can the 

enemy's intentions be so positively determined. 

2. In vtew of these facts, it is i1nperative that 

every possible precaution be taken with regard to controlling the dissem1riat1on ..;:..nd use of radio intelligence in order to 

avoid drying up its sources Any disclosures ln the past with 

regard to the source of radio intelligence have invariably resulted in an immediate change in the enemy's communications 

and the consequent lose of weeits or 1nonths of painstaiting effort on the part of our radio intelligence personnel. It 

is recognized, of course, that radio intelligence ts of no 

value unless proper operational use can be made of it. However, moillentary tactJcal advantage is seldom worth the risk 

of compromising the source, for such compromise will stop the 

flow of information at1d thereby vttally affect operations on ~11 fronts ana in all areas 

3. In urder to further the maintenance of nign secur1 ty in re~ara to radio intelli ence, the following regulations ;)r the dissemination and use of this intelligence are hereby 

pr Peer ib ed: 

(a) The utmost secrecy shall be used in dealing with 

decryption intelligence, 1.e , information resulting from the reading of enemy encrypted despatcnes. 

(b) ~adio intelligence should oe passed on to subordinate commanders only in the form of opera- tional u irectives whenever ,,Jraot 1cable. 

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eclassifi ed and a ursuantto E .0. 1352 
.. . . . .. 

c 0 p y 

-SEGRE'!! 

Se11al 0'525520 

(c) When such intelligence must be given out to 

lower commanders as information it should be 

yassed without any refPrence to its secret 

source and should contain, somewhere near the 

beginning of the message, the Nord 11 ULTRA11 or 

the word 11 ZEAL.11 

(d) Special care must be taken in every command to 

insure that radio intelligence is ~1rovided with 

special securtty safeguards end is sePn and 

hanuled oy the absolute minimum number of ,arsons required for its use Cryptographic systems 

of the highest available security and the narrowest distribution which tncludes the originator 

and sddressees shall always be used for transini tt tng radio intelligence 

(e) Every effort must be made to avoid indicating 

any connection between the source of intelligence and the outcome of operations. When action is 

oased on radio intelligence, local commanders 

will insure that the action cannot be traced to 

this source of intelligence alone. All copies or 

radio intelligence messages should be destroyed 

by burning as soon as possible after being rPaa. 

Ships at sea, where enemy action is possible; snould take particular precautions to destroy 

all evidences of intelligence sources in Jrder 

that there inay be no possioility of t.helr falling into enemy nands. 

/s/ E. J. KING 

CoI?Y to. 

The Commanaer, South ?acific Force. 

The J.Jirector of Naval Intelligence 

The Jirector vf Naval Communications 

By Officer Courier. 

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SECRET