Notes on Sources
The NSA History Collection consists of manuscripts, memoranda, studies, and interviews related directly or indirectly to the cryptologic history of the United States. The extensive records in Series III (1919-39), Series IV, pertaining to the years of World War II, and Series VII, a special series, upon which I have drawn for my research were collected by former NSA Historian Henry F. Schorreck.
Also included within the files of the history program are important special collections of personal papers including those of William F. Friedman and Carter W. Clarke. These collections, however, have remained intact apart from the index system and have their own finding aids.
Other archival collections which have also proved invaluable are the National Security Agency Cryptologic Archives, Ft. George Meade, Md.; the Classified Naval Archives, Washington Navy Yard, Washington, D.C.; the Roosevelt Library, Hyde Park, New York; the Naval Security Group Repository, Federal Records Center, Naval Weapons Supply Center, Crane, Indiana; the U.S. Naval Academy Library; and of course the National Archives, Washington, D.C., which houses Record Group (RG) 457, the NSA collection. I would like to make special acknowledgment to Brian von Swearingen, the Naval Security Group Historian, for his courtesy and his enthusiastic support in obtaining records of OP-20-G from Crane; to the personnel at the Naval Academy Library for their help in locating obscure works in their extensive collection on the history of naval planning and access to their invaluable microfiche records of the Orange Rainbow plans, and to the assistance of the historian at the Classified Naval Archives for alerting me to the Hart diary and to the records of Orange Rainbow and other prewar planning initiatives taken by the U.S. Navy.
Of the million or more pages of documentation supplied the National Archives by NSA, I have drawn extensively on the following series as they pertain to Japanese matters: the SRH series containing narrative materials pertaining to cryptologic history, the SRN series, which consists of individual translations of Japanese Navy messages; and the SRMN series, which represent discrete records of historical cryptologic impact originated by the U.S. Navy. All of this material can be found in RG 457. Within the body of these records, after the translations of Japanese Navy messages (SRN series), two publications stand above all others: SRH-012, John V. Connorton's effort on Japanese diplomatic messages, which is Volume I of his monumental work entitled "The Role of Radio Intelligence in the American-Japanese Naval War," published in 1943, and SRMN-012, the Combat Intelligence Unit, 14th Naval District Traffic Intelligence Summaries, published daily after 16 July 1941, with comments by CINCPAC Fleet Intelligence and CINCPAC War Plans.
Finally, it should be apparent that some of my material concerning cryptologic operations in Hawaii and the Philippines has been drawn from personal experiences. For this I am indebted to the NSA Oral History (OH) program administered by the late Mr. Robert Farley. Copies of all interview cited are located at NSA.
The noncryptologic elements of this chapter in COMINT history necessarily drew on the perspective of many others, from diarists to distinguished historians, to reconstruct plausible cause and effect relationships between historical and cryptologic developments. Since the result is, I believe, a unique view, particularly of the final months of 1941, made possible by heretofore unexamined material, I must take full responsibility for its conclusions.
Two of the military service official histories were very useful. The official Navy history was of significant and continuing value. Samuel Eliot Morison's History of U.S. Naval Operations in World War II provided invaluable perspective on world disarmament and Japanese relations with China, as well as precise details on Japanese Navy and Army order of battle in the western Pacific on 7-8 December 1941. Of necessarily lesser importance in what is essentially a Navy-oriented history, but still valuable, is Louis Morton's treatment of Japanese preparation for war and opening strategy in the U.S. Army in World War II, The War in the Pacific: Strategy and Command: The First Two Years, which also provided the inspiration for some of my illustrations.
In addition to many fine American authors such as Gordon Prange, Edwin Layton, Clay Blair, Jr., Jeffrey Dorwart, and James Leutze, the biographer of Admiral Thomas C. Hart, to name but a few, I also benefited immensely from the work of two English authors, H.P. Willmott and Christopher Thorne. Their books, Empires in the Balance and Allies of a Kind, respectively, provided profound commentary on Japanese motives, aspirations, and planning.
The other secondary sources deserve separate and special mention. Almost before the fires were extinguished at Pearl Harbor, the executive branch of the U.S. government, as well as the Navy and the Army, had launched investigations into this terrible disaster. All of the reports generated by this activity were consolidated into a single, massive, thirty-nine-volume (plus appendixes) reports of the 79th Congress entitled "Pearl Harbor Attack, Hearings before the Joint Committee on the Investigation of the Pearl Harbor Attack." Cited herein as PHA, such material was most valuable in preparing this history. For the period before the war, I am equally indebted to an unpublished manuscript prepared by the late Jack S. Holtwick, Captain, USN (Ret), entitled "Naval Security Group History to World War II." This manuscript, which has been turned over to the National Archives, would have been listed as a primary source if all the documents uncovered by Holtwick could be examined by other historians.
Two sources which I could not locate would have added significantly to this history: Corregidor's records, which were probably burned, and records from Washington which discuss the relationship between OP-20-G, ONI, and War Plans during the days before Pearl Harbor. Despite their obvious value and importance to this story, I doubt if anything will ever again match the satisfaction of finding in Gordon Prange's book At Dawn We Slept the name of Lieutenant Commander Suguru Suzuki, who had been a Japanese spy at Pearl Harbor until early November 1941. The satisfaction came because I had already encountered his name in messages on 18 and 19 November 1941, as he was being transported to Hittokapu Bay probably to deliver his report.
I would like to thank all the members of the former History and Publications Division, particularly Henry F. Schorreck and Gerald K. Haines, for their encouragement, guidance, and timely criticism in the construction of this history. They overcame my initial misgivings about preparing still another history of this period and convinced me that the Agency's archives contained unique and undiscovered treasures.