What Did FDR Know? – Part 2

HTH Nov 30 1941
Hilo Tribune Herald, November 30, 1941.

The above: a front page published one week BEFORE Pearl Harbor.

OK… So the newspaper was published on Hilo.

Well, then, how about a second front page?  And from a different island this time – Oahu.

Pearl Harbor is on Oahu.

Honolulu Advertiser
Honolulu Advertiser, November 31, 1941.


To continue with “What Did FDR Know?”, let’s go over some once secret stuff, shall we?

And stuff that wasn’t so secret – like the headlines above.  These NEWSPAPERS were in newsstands or tossed onto front lawns a WEEK before the attack on Pearl Harbor.  How can that be when our textbooks and history tell us our Navy and Army were caught with their pants down?

It may be fascinating and perhaps eye opening for some of you.  To some of you old hats in military history, not so eye opening.

This story will be centered on “MAGIC”, the cover name given to the secret diplomatic messages sent between Japanese diplomats and intercepted.(¹)

MAGIC intercepts will be the foundation for this story and subsequent ones.

The Japanese diplomats sent message after message believing their code was secure.

They were wrong.


But first, some background on Pearl Harbor itself.  It’s important in your quest to conclude on “What Did FDR Know?”

Adm. Richardson

Before December 7, 1941 and as we read in Part I of this series, did you know the Pacific Fleet was based in San Diego?  The powers to be moved the fleet from San Diego to Pearl Harbor.  Even the decision to move the Pacific Fleet to Pearl Harbor was suspect at that time.  And have you thought about who was commanding the fleet  before the hapless Admiral Husband Kimmel  at Pearl Harbor?

Admiral J. O. Richardson was Commander in Chief, CINCPAC as of January 1940.  Per the “Final Secret of Pearl Harbor”, Richardson was the foremost expert on Japan and studied ad finitum Pacific naval warfare and mostly, of Japanese naval strategies.  He also knew well of Japan’s pattern of secret attacks.

Richardson disagreed with FDR’s opinion that basing the Pacific Fleet at Pearl Harbor was indispensable towards protecting American interests.  Richardson stoutly disagreed and said, “I came away with the impression that, despite his spoken word, the President was fully determined to put the United States into the war if Great Britain could hold out until he was reelected.”

He asserted that Pearl Harbor would be a “… g_d d_mned mousetrap”.  His belief was the fleet should remain on the West Coast in San Diego; out at Pearl Harbor, the fleet would be a strategic target for any Japanese surprise attack which he correctly foresaw.  His opinion was because not only did Pearl Harbor lack adequate fuel dumps and repair facilities, the Fleet lacked sufficient personnel and the waters around Pearl were unsuitable for training.  The fleet would need to return to San Diego and the like for such purposes.

Those who chose to ignore Richardson’s educated opinion did so by saying Pearl’s shallow harbor would preclude torpedo plane attacks amongst other things.

Adm. Kimmel

Richardson asserted too strongly.  Although Richardson was highly qualified militarily, FDR removed him from command on January 19, 1941.  (Similar events are taking place notionally even today; about 200 top military commanders have been removed or forced out by the current Adminstration.)  FDR replaced Richardson with the more amenable Admiral Kimmel.  He was far down the list of able commanders but was still selected by FDR to run the Pacific Fleet.  While he somewhat shared Richardson’s belief, he was obedient as FDR expected.  Kimmel also wrongly assumed he would be “kept in the loop” by FDR insofar as military necessities, including intel.  Was he expendable career-wise?

…and that is how Kimmel ended up in command of the Pacific Fleet on December 7, 1941.


This is a copy of the actual PURPLE message and is the first part of the 14-part message which was delivered by the Japanese to the US Government on December 7, 1941 – late.


The Japanese military, just like the US military, had “secret codes” as did diplomats.  For the purposes of this blog, we will concentrate on two groups of code: the Imperial Japanese Navy’s code (JN-25) and of the Japanese Foreign Office (code named “Purple”).

Talking about Communications Intelligence, or “COMINT”, would take a number of blogs; indeed, entire books and papers are written about COMINT during this time.  For purposes of this blog, allow me to say COMINT is the acronym covering the analysis and usage of an enemy’s radio communications.  Codes are when words are replaced by groups of letters or digits and are usually manual.  A cipher, however, is the replacement of individual letters or groups of letters according to a plan; it is much more complex and are based on machines.

During this time, US COMINT was somewhat loosely organized, largely due to the rivalry between the US Navy and Army.

However, the cover name “MAGIC” was given to the intelligence obtained by both services involving the Japanese Foreign Ministry radio messages.  While at the embassy level, great amounts of military information – and espionage – was disclosed in these secret messages and were therefore at the disposal of the US Government and military.

Imperial Japanese Navy JN-25

The US Navy began its covert intelligence gathering in the early ’20s when they actually broke into the Japanese Consulate in NYC and copied the secret Japanese code in use at that time.  By 1926, the US Navy had broken the Japanese navy’s “Flag Officer’s Code”.  The Imperial Japanese Navy at that time conducted fleet maneuvers about every three years; they would send coded messages throughout the maneuvers.  The US Navy, by virtue of having broken the Flag Officer’s Code, easily listened in on them.

Their “listening in” on the Japanese fleet was so extensive that the US Navy knew of the capabilities of the Japanese warships.  The US Navy knew the speeds, armaments, designs, etc., of the Japanese warships, so much so that the US Navy made improvements to their own warships to counter them.

During this period, the US Navy established a small group within the Office of Naval Communications called “OP-20-G”.  It was formed without extensive knowledge of the US Army as infighting was common.  The same was true for the Japanese military.  Think of the Army-Navy rivalry in football – just grow it tremendously.

While the Japanese navy changed their code along the way, the OP-20-G had little difficulty breaking those, too… until late in 1940.  Knowing they were headed to war with the US, the Japanese navy prudently introduced an entirely new code, the JN-25.  It was much, much more complex than its predecessor.  It proved difficult to crack but they had made progress when… the Japanese navy once again made amendments to JN-25 immediately before the attack on Pearl Harbor.

The US Navy, therefore, was pretty much “blind” intel-wise for pretty much a week before Pearl Harbor.  It would not be broken until March 13, 1942.

But there was another group of cryptanalysts… an ace in the hole.



japanese purple fragment
As the Purple machines were destroyed by the Japanese, this is the only surviving section of an actual Purple machine. National Archives

Alongside OP-20-G, the US Army’s cryptanalysis group called “Signal Intelligence Service”, or SIS, focused their energies on the Japanese diplomatic code.  The group was headed up by William F. Friedman; he was very successful in designing our own encrypted codes.

Japanese diplomats (NOT military commanders) communicated with each other using an existing code designed in 1932; the US cryptanalysts called this code “Red”.(²)  In 1937, the diplomats began using a newer, more complex code; the US referred to this code as “Purple”.  In total, there were fourteen codes used by the Japanese diplomats; two of these were of the most value, Purple and “J-19”.  Purple was used at the embassy level; J-19 was used at the consular level.  Both were machine crypts.

purple analog
The Purple machine, built from readily available parts. It supposedly cost $684.65. Eight were made.  National Archives.

In September 1939, the “unbreakable” Purple code, in the defective thinking of the Japanese, was broken; a key contributor to Friedman breaking Purple was that the Japanese had sent the same message using BOTH Red and Purple codes, a huge blunder in the cryptanalysis arena.  In eighteen months, the SIS, headed up by Friedman, cracked the code(³).  They even BUILT an analog machine from a blank chalkboard which quickly deciphered the “secret” messages.  (The code was so complex that the machine contained 25 connections, which could be arranged 6 pairs of connections, yielding over 70,000,000,000,000 possible arrangements which would determine the method of encryption.)  This was an AMAZING feat to have built a deciphering machine since SIS had not even seen the Japanese one.  Remember, this was 1938.  Nevertheless, these intense eighteen months landed Friedman in the hospital for four months from exhaustion and emotional strain.

With Purple broken, the US was able to immediately decipher all highly secret messages between all top level members of the Japanese diplomats located worldwide… and most importantly, without them knowing.  Given the originators of the messages, they had nearly indisputable validity.  The reach of MAGIC extended to the European Theater of war as well as briefly mentioned in Part I.

These diplomatic communications also clearly indicated espionage was taking place on the west coast of the United States.

Part 3 and 4 will show the contents of MAGIC intercepts so that you can answer on your own, “What did FDR know?”

I hope you will stay tuned.

Part 3 is here.


(¹) Unbelievably, Secretary of State Stimson was definitely upset when he learned we were intercepting messages.  He championed the statement, “Gentlemen, do not read each others mail.”  At the same time, consider the Snowden/NSA “scandals” of today.

(²) Ironically, Hitler had loved Baron Oshima so much he allowed Oshima to purchase a commercial version of Nazi Germany’s famous Enigma machine.  The machine used for Red was based on this Enigma construct.

(³) While Friedman was the man burdened with the responsibility of deciphering PURPLE, it is acknowledged that a man named Frank B. Rowlett was the man who actually broke the code.

49 thoughts on “What Did FDR Know? – Part 2”

  1. The list of FDR’s scandals go back to his early years and continued right thru to his death. Morally, ethically, and legally a criminal – yet the US continued to elect him… incredible. Great post here , Koji!

      1. I thought you were going to “dis-associate” yourself from this blog, good sir! I certainly ask both of you to correct the facts presented at anytime. Thank you!

      1. Lol. You have so much info and data in your head, gpcox, but we feel the same about a certain president… who lies a lot… so I thought you’d throw something in! 🙂

  2. Great post and very well structured.
    I could follow you easily.

    You’re hoping your readers will stay tuned…???


    I will!

      1. Lest we forget my friend…

        These stories deserve a blog of its own.
        But I can wait.
        You know how patient I am.

      1. We owe all this hellish time to the powerful men who were governing us during those times…

        I write so people will remember how little people suffered.

        About my stories…
        Yours are as great my friend even the recipes.

        Have a nice day

  3. Fascinating information. I guess the information you write about was declassified many years after the war and the deaths of the principles involved. FDR died a hero and most people didn’t want to believe anything that would tarnish that image. Afterall, FDR saved the world from the Axis of Evil and got the country out of the Great Depression. The info you presented must have taken a lot of time to research. It was like watching a feature from the History Channel.
    Good job Koji.

    1. Yes, the facts buried, manipulated or classified until after the war. Even recently, after remaining classified were declassified, some documents were again suppressed. But the truth is, FDR did not lead us (your folks as well as mine included) out of Depression. A UCLA study concluded FDRs “New Deal” extended the Depression by seven years – inflated wages, prices and condoning of collusion amongst competing companies. NIRA was also damning as about 80% of industries (excluding farming) freely entered into collective bargaining agreements. FDR took over after Hoover who did not want government getting their hands into business.

  4. Great article ~ I am learning plenty, it saddens me to know that politicians are the same no matter what generation they “serve”, they are only out for themselves and it is the rest of us who suffer. It angers me all those men were sacrificed.

      1. I hope so. I think you missed you calling – you would have made a great history teacher. 😉

      2. He did say once he would much prefer facing the enemy than teach!! You and him both are very knowledgeable.

  5. Oh my goodness, but you’ve done your research! This is really fascinating. I’ve heard “talk” about some of this, but nothing really substantive. I look forward to more. There are so many pieces to the story leading up to America’s involvement in the war, and I think we probably, as a rule, don’t know the half of it! Thank you for this much depth to the story, Koji.

  6. Adm. Richardson’s opinion was soundly based in something that very few people at the time gave any thought to, which was the British surprise attack on the Italian battle fleet in Taranto Italy in 1940. They used torpedo planes at night, carrying torpedoes specifically modified to operate in Taranto’s shallow harbor.

    As for his testimony on what FDR told him, I think it’s rather revealing the Democrat controlled Congress of 1945, only decided off the cuff to hold these hearings on Pearl Harbor after FDR’s death. Because dead men tell no tales, you see. But, even Richardson’s testimony clears FDR if you listen to what he said in the context of 1941 events. No one thought Japan would attack the USA, when merely attacking the now defeated Allies Asian holdings, would have been quite doable without involving the USA. That’s what FDR meant, by ‘as the war goes along, they’ll eventually make a mistake’, meaning…. they’ll attack the USA in some fashion.

  7. Oh, and on the newspaper headlines….. there wasn’t anyone in the world in 1941, that didn’t know Japan was going to move on Asian holdings of Britain, Holland and Australia. As soon as France fell in 1940, Japan occupied French Indo-China, known today as Vietnam/Laos/Cambodia. Then as now, it was the perfect launch point to anywhere and everywhere in the SW Pacific.

    1. Once again, thank you Kevin for your insights on the topic. The goal for me is for a reader to come to his or her own conclusion and you are coming to your own, which is stellar.

      To one of your points, we all know that at least here in the US, commissions were of little use if the goal was to come to the bottom of things. They are just politically driven. Even the commission to determine if Japanese-Americans were due a payment for being imprisoned against their will was one such example – but that’s just my opinion, LOL.

      I hope you’ll continue to keep posting your thoughts!

      Thank you again.

      1. Thanks! I have heard most or all of the explanations for the internment of Japanese-Americans, and it still doesn’t hold water….lol

  8. I don’t know what’s more troubling–our history, the way it’s been taught to us, or the fact that the misleading still goes on today and will be mis-represent/mis-reported/mis-taught in the future. Thanks for this excellent series, Koji.

  9. Haven’t had time to read every word, but as you know from studying history, there is someone somewhere who has predicted practically everything that subsequently occurred. Might be the only time in his life that he was right, but he is always dredged up post mortem and held up as the smoking gun or whatever. Many more people were predicting Phlippines, Panama Canal, Aleutians, etc, than were predicting PH. When sitting in FDR’s, or any other high level US decision maker at the time, and looking forward without knowing the future, PH was pretty far down the list of possibilities. If Richardson or anyone else had predicted the PH attack, when viewed in context, it was only one of many predictions. Since we now know that happened, it’s easy to zero in on that and say “see, see, he knew”. Just my $.02 as the son of a USMC G-2 officer.

  10. You and I know, FDR not only knew what was happening, he helped plan it with his choke-hold on Japan. Even an officer from the Dutch notified Washington as to where the Japanese fleet was and headed for Hawaii. Hard to believe some people still refuse to see all those trees in the forest!!

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