Japanese intelligence/counter- intelligence

[HMan]

The US had some huge intelligence successes in the PTO. Did Japan
ever have any intelligence coups, whether through spying, code-breaking
or other means?

The book "Final Victory" by Stanley Weintraub says that there was several
times Japan should have discovered their codes were compromised. For instance,
a spy discovered there diplomatic code was being read by the Americans.
Astoundingly, they chose to believe their most critical code was safe, and did
not change it.

After Midway, the Chicago Tribune published a story strongly implying that
Japan's codes had been broken. Japan did not change their codes.

I am somewhat leery of this book since it is not a military history, but a history
of the US presidential campaign of 1944. (The context for discussing codes
is that Dewey wanted to use US code-breaking as a political issue to charge
that FDR bungled at Pearl Harbor. He was strongly dissuaded by US military
leaders. They told Dewey that this would not only compromise Pacific operations,
but also the ETO since the Japanese ambassador in Germany's cables were an
intelligence source).

The book also claimed that the Japanese army's codes were more difficult to
break. Was this because the Japanese army was more security conscious,
or another reason such as the biggest allied force in the PTO, the USN was
more concerned with naval codes?

[rcocean]

According to "Combined Fleet Decoded" the Japanese Navy DID change their codes after Midway in August 1942. However, the change was not due to anything the Tribune printed. And the Japanese navy continued to change their codes throughout the war. However, they never changed them enough, and the Allied codebreakers were always able to read their messages with some delay.

I'm surprised the Japanese didn't make a massive change after the battles around Guadalcanal. Given how many times the US Fleet showed up the intercept the "Tokyo express" you'd think the Japanese would've concluded their code was broken. But maybe they blamed it on the Coastwatchers or Allied subs.

[cstunts]

Hello,

"...The book also claimed that the Japanese army's codes were more difficult to
break..."

That was correct. I cannot say why, because I don't care about this area, but it is accurate.

The IJN did have early-war successes [as in the NEI Campaign] with some types of what I will loosely term "Sigint" but it's still a hazy area, and I am too busy right now to investigate that subject. However, I do think it would yield some very interesting & valuable material to a serious--not merely a cybercentric--researcher.
Also, the Japanese had a very large, well-developed and reasonably efficient spy network in the Far East...One well-embedded within Malaya as well as the Dutch East Indies. There is abundant literature on that, and has been since the Forties. (Needless to say their espionage work in China & Manchuria, etc. was organized & pervasive, too. This was part & parcel of the background to their involvement in organized illegal drug manufacture, smuggling, and distribution, of course.)
What is fascinating there, however, is the degree of interservice rivalries within the Japanese military branches in intelligence-gathering & espionage in China/Manchuria which often led to IJN and IJA operatives regarding one another as potentially lethal adversaries. Some quite astonishing cloak-and-dagger stuff between the Japanese themselves which is little known in the West...Obviously the great complicating factor there was Soviet Russia.

There are English language books available on the Army's codes (Kotani & others, or maybe Kahn or someone like that), which might explain why the IJA codes were more secure. I don't pretend to recall, however.

[Takao]

A good start:
https://books.google.com/books?id=8lD5A ... en&f=false

[Carl Schwamberger]

Several books on my shelf indicate the Japanese Navy often changed their fleet operations code, the JN25 in the US lexicon, before each major operation. That is the core code was not changed but the code keys were all discarded & a new set issued. They did one of these changes in March, & that shut the USN intel out of the JN25 traffic until after the Tokyo raid in April. The raid contributed to breaking back into the JN25. When the raid occured the Japanese home fleet sent a mass of messages in a hurry. Many were redundant and many sloppily encoded in the haste. Those errors gave the US code breakers enough cribs they could decrypt the message traffic again.

Alan Stripp was a British 'codebreaker' through the war. In his book 'Code Breaker in the Far East' he describes a fair amount of technical detail about Japans military & diplomatic codes/encryption. He lists the following Japanese codes that were identified by the Brits. These were not all the codes or ciphers used by Japan. Just those Stripp worked with or became aware of in researching his book:

1. JN14. Naval code, often used for coastal ship movements & less oft for fleet activity. Broken during or before 1942

2. JN147. Replaced JN14 in 1944

3. JN23. Code for administrative traffic concerning ship construction, refit, training. Described as three different sucessive codes with the same Allied name.

4. JN25. Used for fleet movements. Stripp claims it was first broken in 1939, tho penetration was "spotty" until 1942. This was the code for the messages that warned of the raid into the Indian Ocean, and the Midway operation in 1942.

5. JN36 & 37. Cipher for Metrological messages. Broken in 1942

6. JN40. Code for merchant vessels to report air and submarine attacks. Broken in November 1942. Gave useful info for location & routes.

7. Unnamed Naval Code. Not broken until 1944. Was a 'book code', which in this case used a English language version of the Bible. Stripp does not identify its use.

8. Unnamed Naval Cipher. Use not identified, other than it carried a few important messages to the end of the war. Not broken?

9. CORAL. A machine cipher used by naval attaches. Broken by the US circa April 1943.

10. Unnamed cipher used only by the naval attache in Berlin. Broken jointly by a combined US/Brit intel unit in March 1944.

11. Unnamed. Army Water Transportation Code. Used to coordinate IJA controlled cargo ships. Broken into in March 1943.

12. KA KA KA (Japanese Name) A Army field or tactical code observed in use in New Guniea. Broken in 1942, but the keys were frequently changed shutting out Allied intel until repenetrated.

13. Unnamed Army Code. Broken "in part" in 1943 & read with difficulty thereafter.

14. Army Address Code. Seperate code used to secure the sending and destination unit for messages secured in other codes. Not Broken??

15. Army chief Administrative Code. Not broken until 1944 when a complete set of documents and encoding equipment were captured.

16. JMA. Military attache code. Broken by Brits in 1943.

17. J19. Diplomatic code used for low level traffic. Broken when introduced in 1941.

18. PURPLE. Complex machine cipher used for high grade diplomatic traffic. Broken by the US in the 1930s. Stripp takes a moment to slam Friedman as "completely wrong headed" in his description of PURPLE. This was the system used by Ambassador Oshima to send detailed reports from Berlin to Tokyo, including a early 1944 description of the fortifications on Normandys beaches.

19. GEAM used by Japans administrators of occupied territories. Entirely administrative reports.

20. Unnamed diplomatic code. Mostly observed securing radio traffic between the Japanese embassy in kabul Afganistan & Tokyo. Carried espionage reports/requests. No clear when it was broken.

21. Unnamed, Used mostly for Navy air transport and reconissance missions. Broken in late 1942? Often read in 1943 by Australian radio intel stations.

22. Unnamed. Airforce metrological code. Broken early or prewar. Was very useful to Allied airforces.

23. Unnamed. Army air force "main code". Broken by Brits in 1944.

24. ABC (British name) Low grade code used for weather, recon, admin traffic. Broken early and often

25. BULBUL. Either evolved from or replaced ABC. Same traffic items. Broken in 1944. Replaced same year by unidentified code which was not broken.

26. Unnamed Army air force or Army code. Used often & widely. Stripp does not indicate when it was broken, but possiblly in 1945 with documents captured on Okinawa.

27, 6633 (Japanese name) Army Air Force code for operational messages of squadron and higher. Above the grade messages the BULBUL code was used for. Broken after documents were captured in the Solomons mid 1942

26.

[steverodgers801]

Another great book is "combined fleet decoded"

[Carl Schwamberger]

...

The book also claimed that the Japanese army's codes were more difficult to
break. Was this because the Japanese army was more security conscious,
or another reason such as the biggest allied force in the PTO, the USN was
more concerned with naval codes?

Tough to say. As the list I posted indicates there were many codes & used in very different circumstances. It also shows the Brits were putting a lot of effort into this as well as the USN & US Army. However resources were far less in 1941 & 42 than in 1944 so priority went to attacking a few of the highest priority message channels/codes in 1941-42.

[rcocean]

The US had some huge intelligence successes in the PTO. Did Japan
ever have any intelligence coups, whether through spying, code-breaking
or other means?

You could start with Pearl Harbor and the Philippines where the Japanese seem to have know everything about the US Forces there, including MacArthur's shoe size.

There were also very good, late in the war, in determining where the US would attack next, including the timing of the B-29 raids. The latter was due to analyzing radio signal traffic. They correctly guessed we would invade Iwo Jima, Okinawa, and were planning to invade Southern Japan.

However, good intelligence without adequate force usually has little impact.

[OpanaPointer]

Yoshikawa Takeo's espionage on Oahu was a classic. He wandered about freely, even flying over Pearl in a civilian aircraft.

[steverodgers801]

Colonel Tsugi also did a fantastic job scouting out Malaysia

[gambadier]

The is a book that documents a British officer as being a Japanese agent, recruited some years pre-war and providing very useful information during the Japanese invasion of Malaya. However, it appears that he was detected, court martialled and then executed by military police on the quayside of Singapore harbour the night before it fell. Allegedly there is no surviving documentation, which at first thought is reasonable. However, its often forgotten that the only people evacuated from Singapore were the intelligence officers, and its difficult to believe that there was no record, unless there was a deliberate decision to forget the matter.

[OpanaPointer]

There are English language books available on the Army's codes (Kotani & others, or maybe Kahn or someone like that), which might explain why the IJA codes were more secure. I don't pretend to recall, however.

I have Ken Kotani's Japanese Intelligence in World War II, but haven't read it yet.

[Takao]

The is a book that documents a British officer as being a Japanese agent, recruited some years pre-war and providing very useful information during the Japanese invasion of Malaya. However, it appears that he was detected, court martialled and then executed by military police on the quayside of Singapore harbour the night before it fell. Allegedly there is no surviving documentation, which at first thought is reasonable. However, its often forgotten that the only people evacuated from Singapore were the intelligence officers, and its difficult to believe that there was no record, unless there was a deliberate decision to forget the matter.

Patrick Stanley Vaughn Heenan.

Google him or see this thread over on WW2Talk: http://ww2talk.com/forums/topic/20908-k ... e-traitor/

Also worth a read: http://www.abc.net.au/4corners/specials ... lphick.htm

[Carl Schwamberger]

...
There were also very good, late in the war, in determining where the US would attack next, including the timing of the B-29 raids. The latter was due to analyzing radio signal traffic. They correctly guessed we would invade Iwo Jima, Okinawa, and were planning to invade Southern Japan.

However, good intelligence without adequate force usually has little impact.

Or not understanding the enemies capability. Dolittle in his autobiography offers this: The Japanese navy signals intercept service monitored some transmissions from the carrier Hornets destroyer escorts in April 1942, the location DFs placed them a bit NW of Hawaii, the fragments intercepted suggested a operation into the NW Pacific. Naval intelligence concluded this indicated a possible raid on the Japanese home islands, with the most likely date as 19 April & the possible dates falling from the 18th to 21st. HQ of the home fleet took that under advisement & reacted by alerting the warships under its control to be ready to sortie on a few hours notice on those dates. they also move the picket ship line eastwards from 300 nautical miles to 600 nm from the home islands. they knew the maximum effective strike range on the US carrier strike groups was barely 300 nm, a 600 nm picket line gave them close to 12 hours extra warning before the hypothetical US carriers reached strike range. I dont think anyone here needs a description of how this worked out for the IJN.