[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 
 
Page 427 
 
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). 
 
Page 428 
 
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.  
 
Page 429 
 
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  
 
Page 430 
 
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 
 
Page 431 
 
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