Location of Japanese Aircraft Carriers:

One of the more interesting false claims about Pearl Harbor regards the organization of and location of the Japanese Navy’s aircraft carriers.

For the record, the First Air Fleet was created on 10 April 1941. As formed, it initially consisted of Carrier Divisions (CarDivs) One (Akagi and Kaga), Two (Soryu and Hiryu), and Four (Ryujo). Carrier Division Four was intended only as a temporary component of the First Air Fleet. Japan’s two newest aircraft carriers—still under construction in April 1941—were the Shokaku and the Zuikaku. These two carriers would, in due time, become Carrier Division Five. Once completed Shokaku and Zuikaku were placed into commission, Carrier Division Four (Ryujo) would be detached from the First Air Fleet. A new carrier division, composed of Japan’s two newest carriers, would then become part of the First Air Fleet. By September 1941, the First Air Fleet was composed of Carrier Divisions One, Two, and Five. In 1941, the Commander of the First Air Fleet was Vice Admiral Chuichi Nagumo. (The First Air Fleet is also known as the Kido Butai. The English translation is Mobile Force or Striking Force.)

Exhibit 115 of the Joint Congressional Committee consists of a group of documents claimed to be “Communications Intelligence Summaries Concerning Locations of Japanese Fleet Units.” (8) Part A of this exhibit claims to be “14th Naval District Summaries dated Nov. 1 to Dec. 6, 1941.” As furnished to the JCC, these documents were purportedly produced by the Navy’s communications intelligence (ComInt) unit on Oahu. In early 1941, this highly secret ComInt unit was located on the second deck of the Headquarters building, Fourteenth Naval District. Sometime later in the year, the unit was moved into a bomb-proof facility located in the basement of the same building.

The very first summary, that of 1 November 1941 (see PHA17, p. 2601), states:

“CARRIERS–: The Commander CarDivs was mentioned in despatches from Tokyo and he took a fair amount of traffic on the Fleet Broadcast.”

Here we find a specific reference to a “Commander Carrier Divisions” (plural). There is testimony in the investigations into Pearl Harbor that right up to 7 December 1941 the United States Navy was not yet aware of a type commander for the Japanese aircraft carrier divisions.

The third summary, that of 3 November 1941 (see PHA17, p. 2603), begins with the following statement under:

“AIR – A WE address today broke down as `ITIKOUKUU KANTAI’. The literal reading of this as 1st Air Fleet is correct, it indicates an entirely new organization of the Naval Air Forces. There are other points which indicate that this may be the case. An old call (YOME7) while never identified seemed to be in a high position with respect to the Carriers and the Air Corps. Upon movement of air units to TAIWAN the association of CarDiv 1 and CarDiv 3 with units of the Combined Air Force was apparent. Their association in a command sense between shore based air and fleet air had never occured before but under the concept of an AIR FLEET can easily be accepted. Traffic in the Air Force continues at a high level.”

We have quoted the entry exactly as it appears in the photostatic copy in JCC exhibit 115. One of the “flags” that long ago alerted me that this document may be phony is the poor grammar used in the writing of the document. The word “occured” [sic] is misspelled in this particular day’s summary. This, too, in this writer’s opinion, is another flag. These summaries were allegedly prepared by two officers, both of whom graduated from the Naval Academy. These summaries, it is claimed, were written for Admiral Kimmel. As the story goes, at 0800 daily, Pacific Fleet intelligence officer, Lieutenant Commander Edwin T. Layton, reviewed these daily summaries with Admiral Kimmel in the Admiral’s office.

The single most important point on the ComInt summary of 3 November 1941, however, has nothing to do with spelling errors and bad grammar. The problem is: Until 3 November 1941 this document—taken at face value—appears to indicate that no one at the Navy’s ComInt unit of the 14th Naval District had any idea the Imperial Japanese Navy had formed an “Air Fleet.” To repeat, the First Air Fleet, Kido Butai, was formed on 10 April 1941.

Even before the authors made their first trip to Archives II at College Park, Maryland, one of us “assumed” the Navy’s communications intelligence organization would have known of the formation of the First Air Fleet on or before 10 April 1941.

“SE RI 0 (Akagi) originates a code movement report addressed to SE HE TU, WI TO MI, CinC Combined Fleet and encoded address DA I I TI KO U KU U KA N TA I (#1 Aircraft Squadron). Yokosuka gives this dispatch to Saipan for delivery to #1 Aircraft Squadron. Ref: #20/0314/6960A – SE RI 0 (00100 00111).”

The above has been quoted exactly as it appears on a electronically scanned copy of the original document. This Station “B” Chronology is dated 10 April, 1941. In other words, the intercept operators, the On-the-Roof-Gang enlisted personnel, pulled this information out of the ether on the very day the Kido Butai was formed. (9)

The intercept operators in question were assigned to Intercept Station B. Station B was located on Guam. The Navy’s intercept unit on Guam was under the administrative control of the Commandant, Fourteenth Naval District. Technical control of Station B was assigned to the Navy’s ComInt facility on Oahu. From June or July 1941 to August or September 1942, the officer in charge of the ComInt unit on Oahu was Commander Joseph J. Rochefort. Let us now examine the entries from three daily summaries.

Punctuation and capitalization is reproduced as it appears in these individual documents:

“….CinC Fourth [Fleet] is at Saipan as of the 22nd and it is possible that AirRon 24 may also be present. Slight indications are that one battleship division and two carriers are preparing to proceed to the mandates but so far there has been no signs that the movement has begun.” (Pacific FIO summary of 23 Nov. 1941.) (10)

“AIR – Through the identification of a call made today Genzan Air Corps has been in Saigon since the eighteenth. We believe that other units of the Combined Air Force have moved from Taiwan to the French Indo China Area although this is not yet verified. One or more of the Carrier Divisions are present in the Mandates” [emphasis added]. (C.I. summary of 25 Nov. 1941.) (11)

“FOURTH FLEET – ….Chitose Air Corps is in Saipan and Air Squadron Twenty-four is still operating in the Marshalls. No further information on the presence of Carrier Division Five in the Mandates” [emphasis added].

“AIR – An air unit in the Takao area addressed a dispatch to the Koryu and Shokaku. Carriers are still located in home waters [emphasis added]. No information of further movement of any Combined Air Force units to Hainan.” (C.I. summary of 27 Nov. 1941.)  (12)

Inconsistencies, both major and minor, exist in the above. The Fleet Intelligence Officer’s report of 23 November 1941 states that “one battleship division and two [aircraft] carriers are preparing to proceed to the mandates.” Of major interest is the implication of “preparing to proceed.” This sounds more like cryptanalysis than traffic analysis. A minor inconsistency is that “mandates” (referring to islands mandated to Japan in the aftermath of the First World War), is not capitalized. These summaries from JCC exhibit 115 jump back and forth in referring to the “Mandates” or “mandates” and also “Marshalls.”

The first summary above, that of 23 November, states that “two carriers” meaning two aircraft carriers were preparing to move. From where, we do not know. All we know is that they were “preparing to proceed to the mandates.”


(8) JCC exhibit 115 is published in Part 17, pp. 2601-2671. Part A of Exhibit 115 is found on pp. 2601 thru 2642. Part B, Pacific Fleet Intelligence Officer Reports dated Oct. 27 to Dec. 2, 1941 are found on pp. 2643-2645 Part C, Pacific Fleet Intelligence Memorandum dated Dec. 1, 1941, is found on pp. 2666-2671. All of these documents as published in Joint Committee exhibit 115, were purportedly photostatic copies of the original documents from 1941. Both Admiral Kimmel and his fleet intelligence officer, then Lieutenant Commander Edwin T. Layton, claimed these documents were photostats of the original documents. Many of the documents in Part A, but not all of them, have the initials “HEK” (standing for Husband Edward Kimmel) on the bottom of them.

(9) Declassification authority NND-003002. Document found by Debbie McKane during one of our trips to Archives II in College Park, Maryland. The original is underlined in several places by a red pencil.

(10) Intelligence Report by Pacific Fleet Intelligence Officer, JCC exhibit 115, Part B, PHA17, p. 2643.

(11)  Com14 ComInt summary of 25 Nov. 1941, JCC exhibit 115, Part A, PHA17, p. 2629.

(12)  Com14 ComInt summary of 27 Nov. 1941, JCC exhibit 115, Part A, PHA17, p. 2631. Both the Fourth Fleet and Air headings are contained in the same daily summary.

By Andy and Debbie McKane