The end of the Pacific War historiography of “Atomic Diplomacy” seems destined for a second round of debunking, after the 1980’s declassification of WW2 Ultra files, with what looks like a “Jon Parchell talking to Japanese scholars about Commander Mitsuo Fuchida’s version of Midway” moment. 
That is, an accepted American Pacific War historiography is about to be ‘up ended’ by Japanese language scholarship little/unknown in English language for years after its appearance. In this particular case, the ‘scholarship’ is a 2011 NHK documentary titled as follows:
“Atomic bombing – top secret information that was never utilized”
Currently accessible link:
The NHK documentary answers questions that “Atomic Diplomacy” has never bothered to ask. Specifically “What did the Imperial Japanese Military & Government know about the American nuclear weapon program, when did it know it, and what did it do about it.”
NHK’s documentary lays out the following:
- The Japanese military knew of the Manhattan project in 1943 and started its own nuclear weapons programs (IJA & IJN) as a result.
- The Imperial Japanese Military gave up these nuclear programs in June 1945. 
- The Imperial Japanese Military & Foreign Ministry were informed of the American Atomic test on July 16, 1945 and refused to believe it was a nuclear detonation.
- The code breakers of the Imperial Japanese Army had been tracking the combat operations of the 509th Composite Group including both A-bomb drops. The Imperial General Staff was told of the special message to Washington DC for the Hiroshima attack, sat on the information, and warned no one.
- The Imperial General Staff repeated this non-communication performance for the 2nd nuclear attack on Nagasaki.
Not having Japanese language skills myself, I had a link to a 2013 English language translations of the documentary sent to me by an acquaintance.
They are located here:
(Special Post for August 15 – Part 1) Japan’s General Staff Office Knew About Hiroshima and Nagasaki Atomic Bombing in Advance and Did Nothing, According to 2011 NHK Documentary
SATURDAY, AUGUST 17, 2013
(Special Post for August 15 – Part 2) Japan’s General Staff Office Knew About Hiroshima and Nagasaki Atomic Bombing in Advance and Did Nothing, According to 2011 NHK Documentary
SUNDAY, AUGUST 18, 2013
The author of these posts is an English language ex-pat whose blog was focused upon the Fukashima earthquake and nuclear meltdown.
Too the extent I have been able to validate the NHK documentary, it checks out.
Specifically, excluding Hiroshima and Nagasaki, the 509th Composite Group dropped 49 conventional “Pumpkin bombs” on 20, 23, 26 and 29 July and 8 and 14 August 1945 against 14 different targets in mid-sized Japanese cities.  These operations gave the IJA codebreaking unit that NHK profiled all the time it needed to take advantage of the indifferent quality of the code clerks of the 20th Air Force. In particular, the 20th Air Forces use of uncoded header text starting with a “V” to each message identifying B-29’s as to the island in the Marianas they were based upon.
As NHK put it:
“June 1945. The special intelligence unit noticed something abnormal. They caught mysterious call signs that they had never heard before. Hasegawa says, “They were call signs in V600s. We’d seen 400s, 500s and 700s, and they come from Saipan, Guam, Tinian. But now, V600s. Something was wrong, we thought.”
They were coming from Tinian Island. On the island that had been using call signs in 700s, there was now a new group of B29 bombers using call signs in 600s. What was their purpose? The unit strengthened its monitoring capability to watch closely.
Tinian Island was taken by the US in August 1944. North Field of Tinian Island, which was the base for Japan bombing raids. A special unit arrived there in June 1945 and started using call signs in V600s. It was the 509th Composite Group, which later dropped atomic bombs in Hiroshima and Nagasaki.”
This sort of mistake was the thing that low level intelligence supporting air operations lived by. Called “Y-Service” in the UK’s Royal Air Force (RAF) and copied by the USAAF with its “Radio Squadron Mobile and the US Navy carrier group flag radio teams. This low level signals intelligence system was pioneered by the German language skilled female signals officers of the RAF in 1939-41 first in the Battle of Britain and then fingerprinting the deployment of the Luftwaffe’s night fighter force. The rapid direction finding, listening on open communications and traffic analysis of Luftwaffe unit code headers like those of the 20th Air Force let RAF “WAAF” and Royal Navy “WRN” female auxiliaries build Luftwaffe air order of battle. 
The failures of the 20th Air Force had been picked up in “Ultra” code breaking traffic in Washington DC that resulted in a “Visitation” by War Department Military Intelligence in March 1945 to look at the cryptological security of its code clerks and pilots. Much was found, but the War Department Ultra officers were more involved with control-based intrigue with the Navy against the USAAF’s 7th Air Forces Radio Squadron Mobile than looking at low level vulnerabilities like the Japanese discovered.
So the Japanese Army code breakers had the signals intelligence version of a “ring side seat” for both the Hiroshima and Nagasaki strikes.
The utter failure of the Imperial General staff to act upon intelligence of the Nagasaki strike – which they had both the intelligence to track and the planes to intercept – is a window into the mind set of the Imperial Japanese military for Ketsu-go.
They had to believe there was no second atomic bomb for their decisive battle to happen. So they believed and didn’t act…and Nagasaki died.
This fantasy belief based neo-Samurai fanaticism could only have been broken by a second atomic bomb.
One was not enough.
With the arrival of the English translation of the NHK documentary after the Ultra file declassification’s, believers in “Atomic Diplomacy” appears to now be in the same belief-based situation the Japanese flag ranks were on August 10, 1945.
Sources & Notes:
 Jon Parchell is the co-author of “Shattered Sword: The Untold Story of the Battle of Midway” and Mitsuo Fuchida was the senior flight commander of the First Air Fleet of the First Carrier Division who led the attack on Pearl Harbor and ended the war as a captain. After the WW2 he and Masatake Okumiya co-authored the book Midway, the Battle that Doomed Japan, the Japanese Navy’s Story. (See link: http://www.usnwc.edu/getattachment/612aa0c4-47a1-4107-afbb-17fa992adf59/Reflecting-on-Fuchida-or–A-Tale-of-Three-Whopper)
 The Imperial Japanese Military’ s atomic bomb or “Genzai Bakuden” program had a two separate Army and Navy projects; the Army’s Ni-Go program and the Navy’s F-Go. Neither of these programs produced a working device, despite 1946 rumors about a test near Hungnam, Korea that were later incorporated into the 1985 book “Japan’s Secret War: Japan’s Race Against Time to Build Its Own Atomic Bomb.”
The pages 720-21 of the closing chapter of John Prados’ 1995 “COMBINED FLEET DECODED: The Secret History of American Intelligence and the Japanese Navy in World War II” mentions the IJN F-Go nuclear program.
Mr. Robert Pfeffer, Physical Scientist, U.S. Army Nuclear and CWMD Agency, “Japan Had an Atomic Bomb (Genzai Bakuden) Program in WWII?”, Combating WMD Journal Issue 7, [Spring/Summer 2011] pages 16 – 19
Japanese Atomic Bomb Project, Wednesday, May 25, 2016
 The primary reasons being wishful thinking about American nuclear capabilities, B-29 damage to urban areas removing the industrial means and the higher priority of implementing Ketsu-Go defense plan for Kyushu. “Ketsu-Go” was a series of strategy options outlined in an 8 April 1945 Imperial Japanese Military Directive. It stated that the Imperial Military would endeavor to crush the Americans while the invasion force was still at sea with suicide or “Tokko” forces.
See: Dr. K. Jack Bauer’s and Dr. Alan C. Coox’s “OLYMPIC VS KETSU-GO” Marine Corps Gazette, August 1965, Vol. 49, No. 8., reprinted at the Hyperwar site here:
See also FAS link:
CHAPTER 4 OPERATION KETSU-GO
 It is not surprising that the Imperial Japanese Army was so successful at tracking the 509th Composite Group. The horrid signals insecurity of the USAAF in general and 20th Air Force in particular has been a consistent theme in secret US government cryptographic histories both at the time and immediately after WW2.
SRH-133 — STUDY SECURITY OF 21ST BOMBER COMMAND COMMUNICATIONS, MIS-WDGS MARCH 1945
SRH-254 — THE JAPANESE INTELLIGENCE SYSTEM, MIS-WDGS 4 September 1945
The USAAF suffered from a much smaller base of officers compared to its eventual size compared to the rest of the War Department and this consistently showed up in its code clerks indifferent-to-poor habits in the use of the M-209 Hagelan encoding machine. The M-209 was a US Army medium-level cryptographic system equivalent to the German Enigma. It was used at Division levels and below in the ground forces and theoretically at Wing and below in the Army Air Forces. The M-209 could and should have had a daily change of machine setting to prevent systematic break-ins over long periods. The only theater where this seems to have happened consistently was in General Douglas MacArthur’s SWPA as both Army divisions in England, and USAAF units world wide, had their M-209 messages broken consistently by German and Japanese code breaking units.
Setsuo Fukutomi, “Mathematics and War in Japan.” pgs 153-159 in Mathematics and War, © 2003, Editors: Booß-Bavnbek, Bernhelm, Høyrup, Jens (Eds.) Birkhauser, ISBN:978-3-7643-1634-1
KOTANI Ken, “Japanese Intelligence in WWII: Successes and Failures,” NIDS Security Reports pages 2 – 27
Japanese Intelligence Successes in World War II
Jan 25, 2012
Christos Military and Intelligence Corner blog posts:
Japanese codebreakers of WWII
Friday, July 27, 2012
The American M-209 cipher machine
Friday, June 1, 2012
 The “Pumpkin Bomb” was the shell of a “Fat Man” plutonium bomb filled with over 5,000-lbs of conventional explosive. It’s operational use and combat effects were well documented, if somewhat ignored by succeeding generations of historians compared to the two nuclear strikes on Japan.
THE UNITED STATES STRATEGIC BOMBING SURVEY
THE EFFECTS OF THE TEN THOUSAND-POUND BOMB ON JAPANESE TARGETS A REPORT ON NINE INCIDENTS
Physical Damage Division
Dates of Survey: 20 October-16 November 1945
Date of Publication: May 1947
As well as:
History of 509th Composite Group
313th Bombardment Wing
Twentieth Air Force
Activation to 15 August 1945
 Aileen Clayton’s memoir “The Enemy is Listening” is the bible of the creation of the “Y-Service” and is a “must read” for understanding intelligence support to air forces in WW2. It is also important in helping to frame the bureaucratic intelligence wars between the senior political/flag rank “Ultra” level code breaking, which was all about centralization and control, versus the need for immediate & actionable intelligence for the soldier/sailor/airman/marine.
For more modern “Y-Service” class intelligence scholarship see the following:
Dr Diane Putney, “USAAF Intelligence and the European War – Daylight Strategic Air War in Europe,” found in
Captain Gilles K. Van Nederveen, USAF, “Wizardry for Air Campaigns Signals Intelligence Support to the Cockpit,” Research Paper 2001-03, August 2001, College of Aerospace Doctrine,, Research and Education, Air University, Maxwell AFB AL 36112-6428
John Stubbington, “Kept in the Dark – The Denial to Bomber Command of Vital Ultra and Other Intelligence During World War II,” Pen & Sword, 2010 432 pages, b/w illustrations, hardcover, Electronic Edition Aug 13, 2013, Amazon Digital Services, : B007ZD13CY, ISBN-13: 978-1848841833
 The issue of US Military centralization and control of low level signal intelligence units like the USAAF’s 7th RSM for “detailed analysis” versus the USAAF’s demand for distributed and immediate exploitation, plus the intrigues there in, are detailed in the following declassified Ultra documents:
SRH-133 – REPORT OF MISSION TO HAWAII AND MARIANAS TO STUDY SECURITY OF 21ST BOMBER COMMAND COMMUNICATIONS MIS, WDGS MARCH 1945
SRH-169 – U.S. CENTRALIZED CONTROL OF U.S. ARMY SIGNAL INTELLIGENCE ACTIVITIES
SRH- 200 – OP-20-G FILE ON ARMY-NAVY COLLABORATION 1931-1945 PART 2 (1 JUNE 1944 – 22 AUGUST 1945)