Episode Details

If Seth and I were to define the two main thrusts of our podcast “The Unauthorized History of the Pacific War,” it would be (1) to correct some of the mythology that has emerged over decades, and (2) to see what lessons might be gleaned that could be important were war to break out in the Pacific again.

In my view, our subject for today falls into the second category, because it’s about the impact of strategic alignment and chains of command on operational success.

Station Hypo was one of three main stations the Navy used to listen to and break Japanese naval codes.  Hypo was the phonetic word for the letter “H,” which stood for Hawaii since Station Hypo was the code breaking office located in the basement of the Hawaii Naval District commander’s building in Pearl Harbor.  As an aside, I visited those rooms when I was commodore in Pearl, and they were being used to store furniture for the Pearl Harbor shipyard headquarters building, but we will leave that for another potential future discussion on what’s happened to all these historic sites over the decades.

But germane to this conversation, in the early months of the war the Naval District Hawaii commander reported, not to Admiral Nimitz, but to Admiral King directly.  That would be corrected in the coming months, but since Station Hypo supported combat operations in the Pacific, Admiral Nimitz certainly thought of it as one of his assets, while Admiral King’s staff in Washington saw it as solely and completely theirs, to include Station Hypo’s brilliant leader, Commander Joe Rochefort.

This led to a chain of command problem that would ultimately lead to Rochefort’s dismissal as head of Station Hypo, even after his incredible success leading to our victory at Midway.

To help us unpack all of this, to include how Station Hypo fed both King’s and Nimitz’s strategic picture, we are proud to host the chief historian of the Navy and Director of Naval History and Heritage Command, retired Rear Admiral Sam Cox.

Admiral Cox, welcome.

Station HYPO:

• What was HYPO?
• Initially known as Fleet Radio Unit Pacific, or FRUPAC
• Hawaii location for the Navy’s cryptanalysts who monitored radio intel of the Japanese.
• HYPO was one of two major stations for Allied radio intel, the other being in Melbourne, Australia.
• Under the command of DC, not Nimitz, or Kimmel for that matter.
• Conspiracy theory that HYPO never had a PURPLE machine, and therefore was unable to read Japanese traffic pre-Pearl Harbor.
• NOT TRUE.  Purple was the diplomatic code, not the Naval code so HYPO had no reason to have the PURPLE machine in the first place.  It would not have helped them in any way.

• HYPO’s mission after Pearl Harbor, was to decipher the Japanese JN-25 code. 
• Prior to Pearl, HYPO was to decipher flag officer’s code and weather codes
• Washington worked on JN25 initially
• How much of the code was readable? 
• Prior to Pearl, they had successfully broken a part of the code, only 10% before the attack.
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• Who was HYPO’s CO and what kind of a man was he?
• Joseph Rochefort was a Naval enlistee, who never graduated high school.  He enlisted in 1918, lied about his age and was later commissioned an Ensign in 1919.  Spent several years at sea as well as a year in Tokyo as a language officer.
• He began work in Cryptanalysis in 1926
• Rochefort was assigned as head of HYPO in March 1941 by Intel officer Laurance Safford.
• Brilliant man who had a knack for solving crossword puzzles and figuring out different types of word puzzles.
• WAS NOT an eccentric as has been shown in movies.
• YES, he wore a smoking jacket while at work, only because it had pockets for his pipe and tobacco
• YES, he wore slippers at work because