[ARC5] FW: How the U.S. Cracked Japan's 'Purple Encryption Machine' at the Dawn of World War II

Wed Dec 7 21:43:10 EST 2016

My understanding of the Purple Code and Pearl Harbor was that it WAS used to break the 13-page (or 14?) diplomatic message from Tokyo to the Ambassador in Washington prior to the attack.  Deciphering of the final page was finished after the attack had begun – too late to give any advantage to our forces.  

Let us pause for a moment (if we haven’t already today) to think of and pray for those who died during that attack 75 years ago today.  RIP and thank you.

73 de

Gene Smar  AD3F

From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Joe Connor via ARC5
Sent: Tuesday, December 06, 2016 1:45 PM
To: D C _Mac_ Macdonald <k2gkk at hotmail.com>; Mark K3MSB <mark.k3msb at gmail.com>; Andy <w5acm at swbell.net>; ARC-5 Mail List <arc5 at mailman.qth.net>
Subject: Re: [ARC5] FW: How the U.S. Cracked Japan's 'Purple Encryption Machine' at the Dawn of World War II

Yes, the JN-25 code (ie, the naval operational code) was not cracked until shortly before Midway. Breaking that code was why Nimitz didn't fall for the Japanese diversionary attack in the Aleutians. The code-breaking led directly to Yamamoto's death because that's how we knew the details of his planned inspection trip to Bougainville.

I believe the diplomatic code was cracked before Pearl Harbor. That didn't provide advance notice of the Pearl Harbor attack, however.

Joe Connor

On Tuesday, December 6, 2016 1:38 PM, D C _Mac_ Macdonald <k2gkk at hotmail.com <mailto:k2gkk at hotmail.com> > wrote:

I seem to remember that the cracking of the JN-25 did not occur until quite a bit later.

Perhaps that cracking was what led to the killing of Admiral Yamamoto much later and quite possibly the ambush of the Japanese fleet at the Battle of Midway.

* * * * * * * * * * * 
* 73 - Mac, K2GKK/5 * 
* (Since 30 Nov 53) * 
* Oklahoma City, OK * 
* USAF, Ret'd 61-81 * 
** FAA, Ret'd 94-10 * 
* * * * * * * * * * * 

  _____  

From: ARC5 <arc5-bounces at mailman.qth.net <mailto:arc5-bounces at mailman.qth.net> > on behalf of Joe Connor via ARC5 <arc5 at mailman.qth.net <mailto:arc5 at mailman.qth.net> >
Sent: Tuesday, December 6, 2016 08:59
To: Mark K3MSB; Andy
Cc: ARC5 at mailman.qth.net <mailto:ARC5 at mailman.qth.net> 
Subject: Re: [ARC5] FW: How the U.S. Cracked Japan's 'Purple Encryption Machine' at the Dawn of World War II 

Fascinating topic. In retrospect, it may be puzzling that our intelligence experts did not see the Pearl Harbor attack coming, but it's even more amazing that the Japanese never figured out that the U.S. Navy had broken their JN-25 code.

                           Joe Connor

On Tuesday, December 6, 2016 9:31 AM, Mark K3MSB <mark.k3msb at gmail.com <mailto:mark.k3msb at gmail.com> > wrote:

Hi Andy 

“The U.S. ceased and broke a multitude of Japanese secret messages, even some containing the plans for the attack on Pearl Harbor which could have been used to prepare.”

No they didn’t contain the plans.   Purple was primarily a diplomatic cipher,  while the Imperial Japanese Navy used JN-25.  JN-25 was largely unbroken at the time of Pearl Harbor, and as I recall they changed the JN-25 variant a few days beforehand.

We did crack Purple, but it never contained “plans for the attack on Pearl Harbor”.    At most it gave a strong indication that something was going to happen on that day,  but unfortunately nobody seriously thought it would be the Hawaiian Islands.

Could Kimmel have done things differently with the Purple based information he had and thereby significantly mitigate Pearl Harbor?   My opinion is yes he could have,  but he couldn’t have known “the plans” from Purple or JN-25 intercepts.

As a side comment,  did any of you see “Pearl Harbor – The Truth” on Sunday night on the History Channel?   I was not impressed at all with the program.

73 Mark K3MSB

On Dec 6, 2016 2:07 AM, "Andy" <w5acm at swbell.net <mailto:w5acm at swbell.net> > wrote:

In case you have not seen this item...
73 de Andy W5ACM

-----Original Message-----
From: Charlie
Sent: Monday, December 05, 2016 10:19 AM
Subject: How the U.S. Cracked Japan's 'Purple Encryption Machine' at the
Dawn of World War II

However, it did not save Pearl Harbor due to no method to put the
information to use.
The US has all the parts of the information but no system to put all the
parts together.

http://io9.gizmodo.com/how- the-u-s-cracked-japans-purple- encryption-machine- <http://io9.gizmodo.com/how-the-u-s-cracked-japans-purple-encryption-machine-> 
458385664

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