Hagar,

the contents of the above post is a huge hint.

On March 31, 1944, two Japanese flying boats crashed into the sea off the Philippines, killing Yamamoto's successor, Admiral Koga.  A passenger who survived was Vice Admiral Fukudome.  Philippine guerrillas captured Fukudome.  Fukudome posessed a document titled Operation Z, or the Z Plan.  It was the Japanese plan for the defense of the Marianas Islands.

The Japanese made life very difficult and short for the Philippino people until Fukudome was returned back to them.  But the guerrillas realized the importance of that document, so it was smuggled out of the Philippines and was translated by Nisei.

The Japanese were concerned about the missing documents, so Koga's successor, Admiral Toyota made minor changes and renamed it as Operation A-Go.  One significant culmination of this battle plan, that the Allies learned about from the recovered documents led to what we know as The Great Marianas Turkey Shoot.

......and as Paul Harvey said, "and now you know the rest of the story"

I'm glad he said "arguably" as this sort of question is incredibly subjective.
As has already been suggested the enigma codes would be "arguably" more important as the finding of them had a bigger influence on WW2, as a whole, rather than just one battle. Didn't the Japanese use a form of the enigma machine? and wern't their messages being decoded too?

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Indeed & there was a Japanese section at Bletchley Park where much of this work was done. At its peak there were 10,000 people working at Station X, as it was known, from all parts of the world & all walks of life. Many of the decipherers in the Japanese section were Americans. I discovered this & many other facts about the top secret work that took place there during WWII & the vital part it played in the outcome of the war. It was so secret that much of this is still classified & some is still being revealed. The place was completely dismantled & everything including the complex electronic deciphering equipment developed there was destroyed soon after the end of WWII to prevent it falling into the hands of a potential enemy. It's hard to believe now but many of the people that worked there took their secrets to the grave & never revealed what they actually did there even to their spouses or close family.

It's a very interesting place for a visit if you get the chance & set in beautiful surroundings. http://www.bletchleypark.org.uk/ Near Milton Keynes so it's not diffcullt to find.

And another point, radio traffic amounted to operational info, which the codebreakers and analysts attempt to understand to put together strategic pictures of the enemy's intentions.  The Z Plan was a strategic document.  There's a big difference between the two.

Hagar,

point well made.

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A very interesting 'what if?" scenario. There are many other examples & towards the end of WWII counter-espionage was so rampant that it must have been very difficult to know quite what to to believe. I'm told that the German spy network in Britain was uncovered very early on & the spies were persuaded to cooperate by transmitting bogus information to their 'spymasters' throughout the war. In order for them to be believed some of the information in these messages had to be correct but it was apparently a very successful operation & possibly saved many lives. For it to work the actual spies had to transmit these messages themselves as each Morse code operator apparently has their own recognisable "signature" & any other operator would soon have been detected.

I seem to recall that the Germans recovered the plans of the Arnhem disaster intact from a briefcase left behind in one of the gliders but believed them to be a plant. They found it as difficult to believe as me that a senior officer would carry the detailed plans with him on the actual operation.

Well he was a bit Fuked in his dome!



A.