[53]
Section II. JAPANESE ESPIONAGE AT HAWAII
The center of Japanese espionage at Hawaii was the Japanese Consulate
General located in Honolulu. As a matter of regular routine, information
was collected by the Consulate General concerning the location and
movements of United States ships in and around Pearl
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Harbor and concerning defense preparations. This information was
forwarded by the Japanese Consulate General to Tokyo and elsewhere in
coded messages sent via commercial communication companies. A collection
of such messages, which has been decrypted and translated, appears in
Exhibit 13 of this investigation and in Exhibit 63 of the Naval Court.
This collection of messages does not include every such message, but
does fully illustrate the type of espionage reports which were made.
Subsequent to the attack, the incoming and outgoing message log of the
Japanese Consulate General at Honolulu was recovered and translated.
These logs indicate the nature of all of the communications to and from
the Japanese Consulate General and show the frequency with which
espionage reports were sent by the Consul during 1941. A copy of the log
is set forth in Exhibit 62.
It is to be noted that the espionage reports submitted during 1941 by
the Japanese Consulate General became increasingly more detailed and. In
the first week of December, 1941, indicated the likelihood of a surprise
attack on Pearl Harbor. The possession of all of those messages by the
American intelligence services prior to the attack would have been of
inestimable value. Some of them, as will appear later were obtained
prior to the attack. Those obtained, however, although indicating
Japanese interest in the location and movements of ships in and from
Pearl Harbor, did not include those messages, particularly during the
first week of December, 1941, which indicated the likelihood of an air
attack. It may also be noted at this point that those Consulate messages
which were obtained prior to 7 December 1941 were decrypted and
translated in Washington but not at Pearl Harbor.
Illustrative of the type of message sent earlier in 1941 is a report
from Honolulu to Tokyo, dated 10 March 1941, which describes various
vessels seen in Pearl Harbor (Translated by Navy, April 5-Document 1
Exhibit 13). The Japanese interest in the location of ships in
particular areas of Pearl Harbor is demonstrated by a dispatch from
Tokyo to Honolulu. Dated 24 September 1941, requesting reports of
vessels in five sub-areas of Pearl Harbor, and requesting reports of
warships and aircraft carriers at anchor and tied up at wharves, buoys
and docks. Particular request was made for mention of the fact when
there were two or more vessels alongside the same wharf (Army
translation, October 9-Document 2, Exhibit 13). The Japanese Consul at
Honolulu established a code to refer to the location of vessels in
particular areas (Navy translation, October 10-Document 3, Exhibit 13).
Tokyo on 18 November 1941 requested a report n vessels anchored in
certain areas and it directed that the investigation be made with great
secrecy (Army translation, December 2- Document 9, Exhibit 13). A report
was sent by Honolulu to Tokyo n 18 November 1941 setting forth the
warships in the harbor in certain areas, commenting on the [54] presence
or absence of aircraft carriers, and describing in detail the course of
certain destroyers which were observed entering the harbor (Army
translation, December 6-Document 10, Exhibit 13). On November 20th,
Tokyo requested a comprehensive investigation of the Fleet bases n the
neighborhood of the Hawaiian military reservation (Army translation,
December 6-Document 7, Exhibit 13).
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On 24 November 1941 Honolulu reported to Tokyo concerning the Fleet
practice of leaving Pearl Harbor, conducting maneuvers, and returning;
that the Fleet had not remained for a long period of time nor conducted
maneuvers at Lahaina Road; that destroyers and submarines were the only
vessels anchored there; that battleships seldom entered the port of
Hilo, Hanalei or Haneo; that virtually no one had observed battleships
in maneuver areas; and, stated that the Fleet maneuvered for one week at
sea, either to the south of Maui or to the southwest and pointed out
that aircraft carriers maneuvered by themselves. This also mentioned the
times when cruisers and other ships left Pearl Harbor and how long they
were away, and generally how long they remained at Pearl Harbor when
anchored there (Army translation, December 16-Document 23, Exhibit 13).
On November 28th, Tokyo requested intelligence, which was described as
being of major importance, concerning the movements of battleships out
of the harbor, pointing out that if such movements were reported but
once a week, the vessels could have traveled far, and that Honolulu was
to use its own judgment in deciding on reports covering such movements.
As to capital ships, it was requested that reports of the entrance or
departure and length of time at anchor from the time of entry into port
until departure be made (Army translation, December 8-Document 13,
Exhibit 13). On November 28th, Honolulu reported to Tokyo concerning the
B-17 planes at Midway and range of anti-aircraft guns? Observations of
maneuvers by troops, prospective reinforcements of troops at Honolulu
during December or January, and advised of the presence of a cruiser
usually about 15,000 feet south of Pearl Harbor and one or two
destroyers at the entrance of the harbor (Army translation, December 8-
Document 16, Exhibit 13).
The messages sent by the Japanese Consul during the week of 1 December
to 7 December 1941, are of particular significance. A message of
December 1st reported on ship maneuvers and described the place where
maneuvers were held as about 500 nautical miles southeast of Oahu, and
stated the reasons why that conclusion had been reached. This message
set forth the "usual" schedule for departure and return of the
battleships and stated that they left on Tuesdays and returned on
Fridays or left on Friday and returned on Saturday of the following
week, and that all ships stayed in port about a period of one week. In
view of their importance, five other messages sent during the first week
in December, 1941, are quoted in full:
From: Tokyo (Togo)
To: Honolulu December 2,1941 (translated by Army 30 December 1941)
J-19
#123 (Secret outside the department)
In view of the present situation the presence in port of warships,
airplane carriers and cruisers is of [55] utmost importance. Hereafter,
to the utmost of your ability, let me know day by day. Wire me in each
ease whether or not there are any observation balloons above Pearl
Harbor or if there are any indications that they will be sent up. Also
advise me whether or not the warships are provided with antimine nets.
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From: Honolulu (Kita)
To: Tokyo
3 December 1941. (Translated by Navy 11 December 1941)
(PA-K2)
#245 (in 2 parts, complete) (Military Secret).
From Ichiro Fujii to the Chief of #3 Section of Military Staff
Headquarters.
1. I wish to change my method of communicating by signals to the
following:
I. Arrange the eight signals in three columns as follows:
Meaning Signal
Battleship divisions Preparing to sortie 1
including scouts and
screening units.
A number of carriers Preparing to sortie 2
Battleship division All departed between 1st and 3rd 3
Carriers Several departed between 1st and 3rd 4
Carriers All departed between 1st and 3rd 5
Battleship divisions All departed between 4th and 6th 6
Carriers Several departed between 4th and 6th 7
Carriers All departed between 4th and 6th 8
2. Signals.
I. Lanikai Beach House will show lights during the night as follows:
Signal
[56] One light between 8 and 9 p. m. ......................... 1
One light between 9 and 10 p. m. ............................. 2
One light between 10 and 11 p. m. ............................ 3
One light between 11 and 12 p. m. ............................ 4
II
Signal
Two lights between 12 and 1 a. m. ............................ 5
Two lights between 1 and 2 a. m. ............................. 6
Two lights between 2 and 3 a. m. ............................. 7
Two lights between 3 and 4 a. m. ............................. 8
(Part 2)
III. Lanikai Bay, during daylight.
If there is a "star" on the head of the sail of the Star Boat it
indicates signals 1, 2, 3, or 4.
If there is a "star" and a Roman numeral III it indicates signal 5, 6,
7, or 8.
IV. Lights in the attic window of Kalama House will indicate the
following:
Signal
1900-2000 .................................................... 3
2000-2100 .................................................... 4
2100-2200 .................................................... 5
2200-2300 .................................................... 6
2300-2400 .................................................... 7
0000-0100 .................................................... 8
V. K. G. M. B. Want Ads.
A. Chinese rug etc. For sale, apply P. O. Box 1476 indicates signal 3 or
6.
B. CHIC. . CO farm etc. Apply P. O. Box 1476 indicates signal 4 or 7.
C. Beauty operator wanted etc. Apply P. O. Box 1476 indicates signal 5
or 8.
3. If the above listed signals and wireless messages cannot be made from
Oahu, then on Maui Island, 6 miles to the northward of Kula Sanatorium
at a point halfway between Lower Kula Road and Haleakala Road (latitude
20 40' N., longitude 156 19' W., visible from seaward to the southeast
and southwest of Maui Island) the following signal bonfire will be made
daily until your EXEX signal is received:
[57] Time Signal
From 7-2 ....................................................... 3 or 6
From 8-9 ....................................................... 4 or 7
From 9-10 ...................................................... 5 or 8
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From: Honolulu
To: Tokyo
5 December 1941 (Translated by Navy 10 December 1941)
(PA-K2)
#252
(1) During Friday morning, the 5th, the three battleships mentioned in
my message #239 arrived here. They had been at sea for eight days.
(2) The Lexington and five heavy cruisers left port on the same day.
(3) The following ships were in port on the afternoon of the 5th:
8 battleships.
3 light cruisers.
16 destroyers.
Four ships of the Honolulu class and ____________ were in dock.
From: Honolulu
To: Tokyo
December 6, 1941 (Translated by Army 8 December 1941)
PA-K2
#253 Re the last part of your #123.
1. On the American Continent in October the Army began training barrage
balloons troops at Camp Davis, North Carolina. Not only have they
ordered four or five hundred balloons, but it is understood that they
are considering the use of these balloons in the defense of Hawaii and
Panama. In so far as Hawaii is concerned, though investigations have
been made in the neighborhood of Pearl Harbor, they have not set up
mooring equipment, nor have they selected the troops to man them.
Furthermore, there is no indication that any training for the
maintenance of balloons is being undertaken. At the present time there
are no signs of barrage balloon equipment. In addition, it is difficult
to imagine that they have actually any. However, even though they have
actually [58] made preparations, because they must control the air over
the water and land runways of the airports in the vicinity of Pearl
Harbor, Hickam, Ford and Ewa, there are limits to the balloon defense of
Pearl Harbor. I imagine that in all probability there is considerable
opportunity left to take advantage for a surprise attack against these
places.
2. In my opinion the battleships do not have torpedo nets. The details
are not known. I will report the results of my investigation.
From: Honolulu.
To: Tokyo
December 6,1941 (Translated by Army 8 December 1941)
PA-K2
#256
1. On the evening of the 5th, among the battleships which entered port
were __________ and one submarine tender. The following ships were
observed at anchor on the 6th:
9 battleships, 3 light cruisers, 3 submarine tenders, 17 destroyers, and
in addition there were 4 light cruisers, 2 destroyers lying at docks
(the heavy cruisers and airplane carriers have all left).
2. It appears that no air reconnaissance is being conducted by the fleet
air arm.
[59]
FINDINGS
26. Japanese espionage at Pearl Harbor was effective and, particularly
during the critical period 27 November to 7 December 1941, resulted in
the frequent transmission to Japan of information of great importance
concerning the Pacific Fleet, the movements and locations of ships, and
defense preparations.
27. Certain reports sent by the Japanese Consul General via a commercial
communications company at Honolulu in the week preceding the attack
indicated the likelihood of an air attack on Pearl Harbor.
28. It will appear subsequently that various coded messages sent by the
Japanese Consul General at Honolulu, which did not indicate
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the likelihood of an air attack on Pearl Harbor, were intercepted by
Army and Navy radio intercept stations and were decoded in Washington,
D. C., prior to the attack; that others which were obtained at Honolulu
by Naval Intelligence prior to the attack were, with the exception of a
few unimportant messages, in a code which could not be decrypted there
before December 7th; and, that three messages intercepted by Army radio
intercept stations at Hawaii and at San Francisco, which indicated the
likelihood of an air attack, were forwarded to the War Department for
decryption but were either not received there prior to the attack or
were not decrypted prior to the attack. If the United States
intelligence services had been able to obtain and to decode and
translate promptly all of the espionage reports sent by the Japanese
Consul General during the period 27 November to 7 December 1941, the
information so obtained would have been of inestimable value.
Page maintained by Larry W. Jewell, lwjewell@omni.cc.purdue.edu. Created: 12/12/96 Updated: 12/12/96