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Topic: Too Late for Pearl Harbor., An article on the efforts to break JN-25< Next Oldest | Next Newest >
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Larry Jewell Search for posts by this member.
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PostIcon Posted on: Jun. 19 2001,10:27  Skip to the next post in this topic. Ignore posts   QUOTE

"When the Navy cryptanalysts testified that 10% to 15% of the code was being read before Pearl Harbor, that definitely did not mean that they could read that amount of the messages intercepted or even that amount of the words in each message. If a message had been enciphered using the 5% of the additives that had been recovered, it would be possible to read on average 10% of the code groups that fell out from the stripped message. But many messages would have been total blanks, and even the few partially readable messages would have contained many more blanks than words. The monthly reports filed by OP-20-G confirm that at the time of the Pearl Harbor attack, not a single JN-25 message from the previous 12 months had been read. A near-contemporaneous history of the cryptanalytic section of OP-20-G, on file in the National Archives, contains a table of the Japanese naval messages read per month; throughout 1941, the number was "none." The reports also confirm only two other Japanese naval code systems being examined seriously before Pearl Harbor, and neither was yielding any results, either."

See the entire article,Too Late for Pearl Harbor By Stephen Budiansky , at the USNI website.

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Tracy White Search for posts by this member.

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PostIcon Posted on: Sep. 25 2003,1:50 Skip to the previous post in this topic. Skip to the next post in this topic. Ignore posts   QUOTE

Larry's link appears to have been moved behind a "members-only" area so here's a link to the article on DefenseDaily.com .

--------------
Let's see what this does...

Tracy White
http://www.ResearcherAtLarge.com
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Jason Tyler Search for posts by this member.

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PostIcon Posted on: Dec. 09 2004,2:46 Skip to the previous post in this topic.  Ignore posts   QUOTE

Hi, I'm new to this board, but wanted to add in something I used to demonstrate how unlikely it was that the US had any clue of the attack on Pearl Harbor in my classes at University of Missouri...

Carrier Striking Task Force Operations Order No. 1

23 November 1941

To: Carrier Striking Force

1. The Carrier Striking Force will proceed to the Hawaiian Are with
utmost secrecy and, at the outbreak of war, will launch a resolute
surprise attack on and deal a fatal blow to the enemy fleet in the
Hawaiian Area.  The initial air attack is scheduled at 0330 hours,
X Day.  Upon completion of the air attacks, the Task Force will
immediately withdraw and return to Japan and, after taking on new
supplies, take its position for Second Period Operations.  In the
event that, during this operation, an enemy fleet attempts to intercept
our force or a powerful enemy force is encountered and there is a
danger of attack, the Task Force will launch a counterattack.


Intercepts would read like this:
(This is assume that you can read 1 in every 10 words… and got lucky enough to get THIS combination. It should be noted that you might get other combinations, yielding FAR LESS information.)


Carrier Striking Task Force Operations Order No. 1

23 November 1941

To: Carrier Striking Force

… Hawaiian … war … a … Area. … X … Force … taking … Operations. … fleet … is … Task Force will launch a counterattack.


Now, this one would be an nearly obvious comination of impending hostilities, but how about this variant of the same theme:

… proceed … Area … resolute … The … Day … will … on … In … attempts … is … the …

If you see that, it means absolutely nothing…
Just an interesting thought of the possiblity of random chance involved in the surprise aspect of the attack.

Jason
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