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How Breaking Japanese Codes and Ciphers
Affected Naval Operations Against Japan 1941-1945

by John Winton
Naval Institute Press
Annapolis, MD 1994


Reviewed by

CAPT William H.J. Manthorpe, Jr.,  USN(Ret.)

[Editor’s Note: Captain Bill Manthorpe is a retired naval intelli-gence officer with a long and distinguished record of perceptive analysis. Following his retirement from active duty, he served as the civilian Deputy Director of Naval Intelligence.]

John Winton is a noted British maritime author who has written more than a score of fiction and non-fiction books on naval themes, most covering the British Navy in the 20th century. Two of his earlier books, however, were War in the Pacific: Pearl Harbor to Tokyo Bay and Ultra at Sea about the use of Ultra in the Battle of the Atlantic.  Thus, he obviously bas considerable knowledge of the strategy and operations of the U.S. Navy in the Pacific during World War II as well as an understanding of the origins and uses of the communications intelligence (COMINT) which was designated Ultra.

His list of sources for this book indicates that he has consulted Morrison, Potter and Roscoe when necessary to detail U.S. naval operations and shows that he has read Holmes, Layton, Pineau and Wenger for background on the collection, analysis and political· bureaucratic activities influencing the use of COMINT in the Pacific. He does not, however, list among his sources any interviews with those numerous persons still alive who were engaged in breaking Japanese codes and ciphers or who were the intelligence officers and planners benefiting from that work. Thus he neglected a number of primary sources. I have talked to a few of them in preparing this review and have used the background thus gained in assessing Winton’s work.

Winton’s unique contribution to the development of this book is having reviewed the vast store of Special Research documents that have been deposited in the National Archives. Those documents include valuable records from U.S. Navy files such as; organizational histories of intelligence units, reports of conferenc-es, inter-office memoranda as well as topical intelligence reports on the Japanese Navy and translations of Japanese messages. While original sources, it must be noted that the former materials probably contain a considerable amount of personal opinion and the latter are unevaluated information, not intelligence. Thus, while they are primary sources, they do not always provide reliable or definitive ground truth, and so, must be treated with care. More importantly, the archived documents also include the CinCPac periodic intelligence summaries sent to the fleet opera-tional commanders on a routine basis providing analysis of current and expected Japanese force composition and movement based on CO MINT and, often, marked Ultra. This is the information which was available to the planners and operators as the basis for their actions and, thus, should have been of great historical utility to the author.

Winton has intertwined the insights gained from his archival research with his own background knowledge and the information from his secondary sources to produce a very interesting and readable book. Nevertheless, I am informed that, because he did not talk to some of the available primary sources, he has misinter-preted some of that archival material and has perpetuated errors that have been made by past historians who did not have access to that material.

This is an acceptable book for the general reader interested in naval history because it does a considerable service by highlighting for that reader the important role of intelligence, especially COMINT, in facilitating U.S. Navy operational successes throughout the Pacific War. That topic has not received the emphasis it deserves in most past general histories. That is, mainly, because they were written when most of the information was still classified but, also, because they focused on the details of the operations themselves rather than the planning and force repositioning during the periods between them. It is my impression that Winton’s errors are generally errors of detail or nuance which will not affect the overall impression or enjoyment that the general reader takes away from the book.

The book will, also, provide interesting weekend reading for the naval professional, but it is not a book which they will want to add to their library and refer to again and again. It contains no important revelations, makes no significant corrections to past historical research and does not raise any issues that will cause continuing debate. Thus, it does not add appreciably to the background and knowledge that a professional student of the Pacific war already has.

This book was first published in Great Britain and has been picked up for distribution in the U.S. by the Naval Institute Press. It has not been re-edited for U.S. readers . That should have been evident to me from the spelling of cyphers  on the title page. I didn’t notice that, probably because I had seen it spelled ciphers on the dust jacket and the Institute’s publicity. Anyway it did not become apparent until I was well into the book and began to check the jacket and title pages for an explanation as to why I was continuing to encounter the British spellings, syntax and usage that abound throughout the book. Those are not bothersome.

What is particularly annoying, however, is that the book contains no maps of the Pacific and no diagrams of the battles. I had to read it with my copy of Potter at my right hand. It seems to me that the general reader will be totally lost without those aids and naval professionals will want them to refresh their memories and to get the most out of Winton’s descriptions. Another shortcoming that an editor might have insisted on fixing is the lack of footnotes. Winton lists his secondary sources and the original documents that he has reviewed in an appendix. Sometimes, in the text he cites the source of a statement. Yet, too often, it is difficult to tell whether a statement is fact, someone’s recollection or Winton’s opinion. This is especially troublesome in the case of hotly debated topics, for example Halsey’s actions at Leyte Gulf. It is not clear that Winton’s description and conclusions are his own, a critic’s or the official verdict. Understandably, a page filled with superscript numbers would detract from the flow of the text. An editor could have suggested one of several techniques which would have let the book retain its very readable text that the general reader will enjoy but would have provided the documentation that a professional reader desires.

Winton starts his book by introducing Lieutenant Commander Joseph J. Rochefort, the head of the Combat Intelligence Center, the Pacific Fleet’s COMINT Analysis Facility, and Lieutenant Commander Edwin T. Layton, CinCPacFit’s intelligence officer, as they brief Admiral Nimitz prior to the battle of Midway. He then moves to the post-Midway briefing when Nimitz is quoted as stating that “This officer (Rochefort) deserves a major share of the credit for the victory at Midway” . Winton asserts that Rochefort and his team ” …had brought off what was arguably the greatest intelligence coup in all naval history…They also removed for ever any lingering doubts that Communications Intelligence… was a waste of time and effort.”

He then moves back to the period of Pearl Harbor and “the understandable desire to hunt down those who were held to be to blame”. His claims that “The truth was that there had been plenty of intelligence in the months before Pearl Harbor which, with hindsight, can clearly be shown to have revealed Japanese intentions. The failure, it if was a failure, was in evaluating that intelligence and thereafter promulgating it to the operational commanders in the Pacific.” By that brief paragraph, Winton disposes of an issue which has been the subject of numerous books, articles and continuing debate. It is a subject which remains a core study of intelligence indications and warning and national and military decision making. The distribution of this book by the Naval Institute will assure that it gets into the hands of many professionals and students interested in those topics. They are likely to be jarred, as I was, by Winton’s brief treatment and conclusion.

This reader wished that he had spent, perhaps, a page summarizing the various sides in that debate so that his readers could, at least, decide whether they agree with his conclusion, which is not universally accepted. For example, one of the issues in the debate over Pearl Harbor is the conspiracy theory that Churchill had the intelligence and did not pass it to Roosevelt. Some ten pages after his conclusions on Pearl Harbor, Winton discusses British exploitation of the Japanese codes prior to Pearl Harbor. In that discussion there seems to be a misinterpretation, on his part, of the extent to which the British COMINT organization was able to read vice break the Japanese JN-25 code and, specifically, which version of the code they were reading. Thus the reader gets the impression that Churchill could have had the information of Pearl Harbor and the conspiracy theory may be tenable. Yet, some pages later, the reader finds that Winton refers to a British intelligence officer in the Far East at that time who said that his reports of Japanese intentions and capabilities may not have even gotten up the line within the Admiralty, let alone to Churchill. Thus,whether the British had the information or not, the conspiracy theory does not hold up.

But this is not a book or, even, a chapter on Pearl Harbor. The introductory chapter is one of the most important, however, for both the general reader and the professional. They should concentrate, because Winton’s smooth and brisk writing style might cause them to miss some important lessons. For the general reader, his useful lesson is the difference between intelligence, communications intelligence (COMINT), radio intelligence (called signals intelligence-SIGINT-in the U.S.) and Ultra which was a marking for those intelligence materials containing COMINT based on analysis resulting from the breaking or partial breaking of certain Japanese codes. For the professional, his important Jesson centers on the organization of the U.S. Navy’s communications and intelligence efforts, the Washington bureaucratic politics that it created and the impact that politics had on operational success . Indeed, the book is a description of and tribute to work-arounds that were used to assure operational success. That is a Jesson that naval professionals must Jearn from this and other histories or they will, again soon, Jearn it by experience. The potential for organizational and personal politics within intelligence and between intelligence and operations is increasing as we go through a period of reorganization and right-sizing that threatens the existence of organizations and the careers of people.

Following the introductory chapter, Winton proceeds chrono-logically through the Pacific War-Coral Sea, Midway, Guadalca-nal, the Solomons, the Marianas, Leyte Gulf, Okinawa and Japan. In each case, he highlights the role that COMINT played or could not play in each battle. His discussion of the COMINT available and its use highlights that the job was not easy. There were many Japanese codes, intercepts often provided only partial or garbled text, the press of time frequently permitted only traffic analysis based on message externals, and direction finding accuracy varied widely. As a result, intensive efforts were required to generate information and considerable analysis and some inference were required to produce the intelligence that would be marked Ultra. It seems to me that it was not so much “breaking Japanese codes and ciphers” that “affected naval operations against Japan” as it was a Fleet Commander willing to rely on intelligence, excellent personal relationships up and across the Pacific Fleet intelligence chain of command, a bureaucratically courageous leader of the intelligence production organization and a group of brilliant and incredibly hardworking analysts.

There is a chapter on the ambush of Admiral Yamamoto as he flew to the Solomons on an inspection trip. I find parts of the story of the approval chain for the operation to be a bit far-fetched . Nevertheless, Jacking any footnotes or source citations, I will just have to continue to wonder about the decision making ability and security consciousness of the Secretary of the Navy who is said to have consulted “churchmen” before approving the operation.

There are also several chapters on the operations of the British Far Eastern Fleet in the Indian Ocean and southwest Pacific. Those are appropriate, given that the book was developed for British publication. The details were new history to me and helped to give balance to the impression that the naval war in the Pacific was, exclusively, an American war.

Of most interest to the readers of this review. there are also two chapters on the “Submarine War”. For any professional reader, these chapters are the strength of the book. They clearly document the operational success that can come from the availability of good intelligence and a close and harmonious relationship between operators and intelligence personnel. Winton’s account of the poor performance by U.S. submarine torpedoes, the difficulty in getting remedial action from the Washington bureau-crats and the role played by COMINT in finally provoking action is one of his better accounts. I am also informed by primary sources that it is the most complete, accurate and factual. In this case he apparently used one of his secondary sources to very good advantage.

Upon reading these chapters, I was stuck by an interesting characteristic of most naval histories. The names of flag officers in command of carrier and other surface task forces and task groups are always cited. The names of other surface force commanders are only cited when they are unusually colorful or successful, like 31 knot Burke. The names of surface ship, even carrier or battleship, commanding officers are rarely given. But the names of submarine commanders are invariably given. Thus, in these chapters, the longtime members of the Naval Submarine League will find the names of those recipients of the Navy Cross and flag officers they carne to admire as young officers. They will also find the names of other, just as heroic, who did not achieve such distinction. One of those, Ralph Stiles, for example, was my first boss in the Navy and the man who gave me the job that set my course in intelligence.

These chapters also reveal the origin of the close, long standing and mutually beneficial relationship of the submarine and intelligence communities. It began on the initiative of Rochefort and Jasper Holmes, a submariner who worked with him, and it had the unspoken blessing of Layton and the submariner for whom he worked, Nimitz. Winton credits SIGINT, i.e., direction finding against Japanese submarine transmissions, with “the first ever sinking of a Japanese warship by a U.S. submarine”, the 1-173 by GUDGEON . He says that it was Ultra intelligence that provided the opportunity for the first submarine sinking of a Japanese carrier, CHUYO by SAILFISH. These successes in 1943 were the first of many opportunities for sinkings that the submarine community owed to the intelligence community during the war in the Pacific.

Following the war, the close relationship continued and the submarine community paid its debt in full by providing naval intelligence with a series of outstanding officers for leadership positions. One of the commanding officers who is cited as benefiting from intelligence for success in the war was Fritz Harlfinger who later served as DNI. Another Pacific submariner, winner of the Congressional Medal of Honor, Gene Fluekey, also served as DNI. The mutually beneficial relationship of the Submarine Force and Naval Intelligence continued throughout the Cold War by the submarine collection and intelligence analysis of valuable intelligence on the war plans and operational capabilities of the Soviet Navy. Based on their past relationships, it is certain that the two communities will continue to work together for mutually beneficial success in the new era of littoral naval warfare.

This is a good book, enjoyable to read and educational about naval warfare and intelligence. The Naval Institute Press was astute to recognize its value and correct in making it available to us. Nevertheless, it could have been so much better for both the general reader and professional if the Press had done some work on it. I recommend that members of the Naval Submarine League buy a copy for a quick read and then give it to their favorite teenager along with a copy of Potter to begin stimulating their interest in naval history, submarine warfare and intelligence.


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