Joe Rochefort’s War

Title:                  Joe Rochefort’s War

Author:                Elliott Carlson

Carlson, Elliott (2011). Joe Rochefort’s War: The Odyssey of the Codebreaker Who Outwitted Yamamoto at Midway. Annapolis, MD: US Naval Institute Press

LCCN:    2011025666

D774.M5 C28 2011


Date Updated:  February 24, 2016

This book is the biography of Joe Rochefort (Joseph John Rochefort), a major player in winning the Battle of Midway. The success of Rochefort’s team could have been realized only if Admiral Nimitz paid attention to his intelligence analysis. All the credit goes to Nimitz for doing so, for he had to do it in the face of strong opposition from Washington, particularly Admiral King. I have had correspondence with a relative of Rochefort, who bemoaned the raw deal he got, as all of his relatives (and supporters) say he got.

At the Combat Intelligence Unit at Pearl Harbor, a staff of about 30 naval personnel, headed by Lieutenant Commander Joseph John Rochefort, struggled with the flow of unbroken Japanese naval radio messages. There were only two or three cryptanalysts on the staff, and most of the rest were trainees, clerks, aids, and translators. On December 10, three days after the raid on Pearl Harbor, the unit was given the job of beginning an attack on the high-level Japanese naval code known to the Americans as “JN25.” Although parts of the code had been broken, only fragments of messages could be read.

With the outbreak of the war, the small unit began adding personnel, some from damaged ships, so that by May 1942, the staff had ballooned to 120, working 24 hours a day. Some of the key members of the team had studied the texts and reports of William Frederick Friedman and had worked under Laurence Frye Safford at the Navy’s Code and Signal section of Naval Intelligence.

Eventually reaching the rank of Captain, Joe Rochefort was a major figure in the U.S. Navy’s cryptologic and intelligence developments from 1925 to 1947. He headed the Navy’s fledgling cryptanalytic organization in the 1920s and provided singularly superb cryptologic support to the U.S. fleet during WWII, leading to victory in the war in the Pacific. At the end of his career (1942-1946), Rochefort successfully headed the Pacific Strategic Intelligence Group in Washington.

Rochefort was born in 1900 and enlisted in the Navy in 1918. He was commissioned an ensign after graduation from the Stevens Institute of Technology. Rochefort’s tours ashore included cryptanalytic training under both Captain Laurance Safford and Agnes Meyer Driscoll in 1925; a stint as second chief of the Department of Naval Communications’ newly created cryptanalytic organization, OP-20-G, from 1926 to 1929; training in the Japanese language from 1929 to 1932; and a two-year intelligence assignment in the Eleventh Naval District, San Diego, from 1936 to 1938. Until 1941, Rochefort spent nine years in cryptologic or intelligence-related assignments and fourteen years at sea with the U.S. fleet in positions of increasing responsibility.

In early 1941, Laurance Safford, again chief of OP-20-G in Washington, sent Rochefort to Hawaii to become Officer in Charge (OIC) of Station Hypo in Pearl Harbor. The reasons for Rochefort’s appointment were obvious: he was an expert Japanese linguist, an experienced and very talented intelligence analyst, and a trained cryptanalyst.

After the Japanese attack on Pearl Harbor, Rochefort and the Station Hypo experts were eventually able to read enough of Japanese naval communications to provide daily intelligence reports and assessments regarding Japanese force disposition and intentions. During the peak month of May 1942, Rochefort reviewed, analyzed, and reported on as many as 140 decrypted messages per day. These reports went directly to the highest-ranking fleet commanders.

The most significant cryptologic success was the timely and accurate support provided by Rochefort and his unit surrounding the Battle of Midway, considered by many to be the turning point of the war in the Pacific. Station Hypo provided accurate and timely intelligence reports for the rest of the Pacific War; these reports were used by the most senior navy officers for strategic and tactical decisions.

Rochefort died in 1976. In 1986, he posthumously received the President’s National Defense Service Medal, the highest military award during peacetime, for his support to the Battle of Midway.

Reviewed by Hayden Peake.[1]

Joseph John Rochefort was born in 1900 in Dayton, Ohio, the youngest of seven children. Although a good student, especially in math, he dropped out of high school at 17 and joined the Navy to become a pilot. But the Navy had other ideas, and that is the story told in Joe Rochefort’s War. Author Elliot Carlson tells how this eager, opinionated, forthright, sometimes outspoken young seaman survived manpower reductions after WWI, married his high school sweetheart, obtained a commission, and went to sea. Then, by a stroke of luck or sound Navy personnel policy, he was selected in 1925 to attend an advanced cryptanalysis class in Washington, DC. He did well. Between 1932 and 1939, Rochefort learned Japanese in Japan, had sea duty on a destroyer, carriers, and a cruiser, and was assigned to Pearl Harbor, where he became commander of a new codebreaking section called Hypo.

Rochefort’s abilities had gained him strong supporters in the Navy, where Naval Academy graduates dominated the leading ranks. His personality and willingness to challenge superiors also made enemies. Carlson tracks these often conflicting forces as Rochefort worked to establish a code breaking capability under austere conditions. From a personal point of view, the Hypo billet was risky. Intelligence was not career enhancing, and future promotions were not assured. Moreover, in accepting the job, Rochefort had insisted on reporting to the commander at Pearl Harbor, Adm. Husband Kimmel, thus ruffling some feathers in OP-20-G, the Navy’s cryptographic headquarters in Washington. Until Hypo was established, OP-20-G had been the source of Kimmel’s intelligence, a mission it was reluctant to give up. But Rochefort prevailed and made more enemies in the process.

Rochefort assembled an impressive team of codebreakers, several with more ability than he. Hypo Station focused first on the Japanese naval code, JN-25, and then on its more difficult successor, JN-25b. Although it was evident from the results that Japan was planning a major operation in 1941, Rochefort was dismayed not to have uncovered the details by 7 December. By February of 1942, however, Hypo had made significant progress, and Carlson relates how this led to the discovery that an attack on Midway was planned. Despite continuing opposition from OP-20-G, where his superiors did not agree with him, Rochefort used a clever ruse to prove the Japanese navy was about to attack Midway. Admiral Halsey was convinced, and the rest is history.

Halsey recommended Rochefort for the Distinguished Service Medal, but his Washington enemies succeeded in denying him the award. It would eventually be awarded posthumously by President Ronald Reagan. After Midway, Rochefort was summarily transferred to a shipbuilding yard in San Francisco and later to OP-20-G. He did well in both assignments and was eventually promoted to captain. After one more sea duty assignment he retired in 1947.

Joe Rochefort’s War is a story of a talented, sometimes abrasive, but always effective, officer battling the bureaucracy and unjustified criticism in a tradition-bound Navy. RAdm. Donald “Mac” Showers, who worked with Rochefort in 1942, notes in his foreword to this book that it is “an account that is long overdue.” (p. ix)

Well told and well documented, Carlson’s book has done a fine job.

[1] Hayden Peake is a frequent reviewer of books on intelligence and this review appeared in The Intelligencer: Journal of U. S. Intelligence Studies (19, 1, Winter/Spring, 2013, pp. 116-117). Hayden Peake is the Curator of the CIA’s Historical Intelligence Collection. He has served in the Directorate of Science and Technology and the Di recto rate of Operations. Most of these reviews appeared in recent unclassified editions of CIA’s Studies in Intelligence. These and many other reviews and articles may be found on line at


This entry was posted in Codebreaking and tagged . Bookmark the permalink.

8 Responses to Joe Rochefort’s War

  1. My father, Ensign Reed Dawson, was on Joe Rochefort’s staff at Pearl. I was told personally by another officer on that staff, LT William Shaw, that my father had the key insight that broke Jn25. Dawson (B.A., M.A. Ph.D in theoretical statistics, Harvard University), was a lifelong senior cryptanalyst at NSA. Any way to determine truth, falsity, or partial truth of Shaw’s assertion?

    • fredslibrary says:

      It is possible that is true. My experience has shown that it is almost never a single event that provides a breakthrough in breaking a cipher. Ideas bounce off of the team and eventually something is tried that seems to work. I would not take anything away from your father who served at Pearl. It was, for the most part, a thankless, mind and brain numbing experience that could drive people mad. The fact that Nimitz realized the value of the work is the key to the realization of the the work. Rest proud that your father played a key role in winning the Battle of Midway, but don’t rely too much on the fact that he found the one thing that led to breaking the cipher.

      • Judge Mark R. Dawson says:

        My father LT Reed Dawson was not on Rochefort’s staff at Pearl. I have discovered he was assigned to OP-20-G in Washington from 1942-1946, working under LCDR H.H. Campaigne on ENIGMA. Dawson wrote a “top secret-cream” paper entitled “Stepping Patterns of T-Wheels in ENIGMA Motion.” I know Dawson was in Hawaii, probably on TAD, prior to the summer of 1943, but I know no details.

      • fredslibrary says:

        The ENIGMA business is a fascinating aspect of WW II. All those who worked on this project (as well as MAGIC, the Japanese naval code) deserve high recognition. It is sad that political pressures from both the Department of the Navy and from civilian leadership discounted the value of the work. Everyone knew about Enigma machines, for they were commercially available before the war. It was the refinements that the Germans made that drove the codebreakers nearly mad. The addition of a fourth and then a fifth wheel made finding patterns nearlly an act of God. Your father certainly deserves high commendations for his work, and probably didn’t get much during or even after the war. Thanks for letting me know about him.

  2. Bob Biard says:

    My uncle Forrest R. Biard was a Navy linguist who came to Station Hypo in September 1941 straight from two years of Japanese language school in Japan. Prior to his death at age 96 in November 2009, he wrote and spoke often about this experience, and I have given all his writings, tapes, correspondence, and photos regarding WWII to the Museum of the Pacific War in Fredericksburg, Texas (Nimitz’s hometown). Several historians have disputed his writings on certain issues, but not about the group effort that made Hypo’s success and the breaking of the JN-25 possible, or Nimitz’s bravery in accepting the group’s findings (with many kudos to Admiral Layton for making that possible). I’m looking forward to reading the book. It is too bad that the group never got the recognition they deserved, but then they didn’t do it for the recognition.

  3. Harry Williams says:

    The original work on JN25 was done in 1939 by John Tiltman, a British Army officer who had a most distinguished career with the British GCCS (Government Code and Cipher School) and its’ successor GCHQ. NSA published a biography of Tiltman in 2007 (free for the downloading). Tiltman’s daughter and grandsons all live in Hawaii.

  4. Nancy Bearg says:

    My mother was a codebreaker assigned to Arlington Hall Station during WWII. Her main (maybe total) work was with Japanese war messages related to naval activity. Might her office have had a role with Rochefort and his work? I also will ask her! And, I’m looking forward to reading the book and giving it to her.

  5. Pingback: The Battle of Midway | Intelligence Analysis and Reporting

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s