From: U.S. Congress Joint Committee on Pearl Harbor Attack Hearings; Pt.
35, the Clausen Investigation, pp. 52-62.
 UNITED STATES PACIFIC FLEET
U. S. S. PENNSYLVANIA, Flagship
Cincpac File No. HRK
November 27, 1941.
From: Commander-in-Chief, United States Pacific Fleet.
To: PACIFIC FLEET.
Subject: Pacific Fleet Intelligence Bulletin No. 45-41.
Enclosure: (A) Subject Bulletin.
1. Enclosure (A) is forwarded herewith for information.
2. BECAUSE OF THE CONFIDENTIAL NATURE OF BOTH THE SOURCE AND INFORMATION CONTAINED HEREIN, IT IS OF THE HIGHEST IMPORTANCE THAT THE CONFIDENTIAL CHARACTER OF THIS BE CAREFULLY PRESERVED.
3. This information obtained from Naval Intelligence sources has been reproduced by the Commander-in-Chief, United States Pacific Fleet. Any request for additional copies of this document will be made to the Commander-in-Chief and not to the Division of Naval Intelligence
4. Additional copies shall not be made. This bulletin should be retained for study and reference (plus subsequent additions or corrections) during the present National Emergency.
P. C. Crosley
P. C. CROSLEY,
List I, Case 3; P., X.
Atlantic Fleet A1;
Asiatic Fleet A1;
One copy each to:
FATU, NTS, NC4, ND11-ND14
NB49, Rdo. & Snd. Lab.
 TOP SECRET
INTELLIGENCE BULLETIN NO. 45-41
(A) ORGANIZATION OF THE JAPANESE FLEETS ....... Pages 1 to 12 inclusive.
Major Fleet Commands ............................. Page 1.
Combined Fleet and First Fleet ................... " 2.
Combined Fleet and Second Fleet .................. " 3.
Third Fleet ...................................... " 4.
Fourth Fleet ..................................... " 5 and 6.
Fifth Fleet ...................................... " 7.
Sixth Fleet-(Submarine Fleet)..................... " 7.
Carrier Fleet .................................... " 8.
Combined Air Force ............................... " 9.
Train for Combined Fleet ......................... " 10.
Japanese Naval Forces in China ................... " 11 and 12.
(B) JAPANESE FORCES AND INSTALLATIONS IN THE MANDATED ISLANDS, Pages
13 and 14.
Table "A" showing distribution of material and personnel forces
(2 pages to be pasted together)
Sketch of PALAO (PELEW).
Sketch of MALAKAL Harbor, etc.
Sketch of JALUIT Harbor, etc.
 TOP SECRET
(A) ORGANIZATION OF THE JAPANESE FLEETS. October 30, 1941.
The following revision of Op-16-F-2, O.N.I. Serial #27-41 supersedes and replaces the former report on this subject.
The principal change consists of a further increase in the number of fleet commands. This has arisen from the regrouping of aircraft carriers and seaplane tenders into separate forces, and from the creation of special task forces in connection with the southward advance into Indo-China. The regrouping has resulted in a notable specialization within the various commands, as shown below.
MAJOR FLEET COMMANDS
I. Combined Fleet
1 First Fleet (Battle Force) 3 Batdivs, 1 Crudiv,
2 Second Fleet (Scouting Force) 4 Crudivs, 2 desrons,
3 Third Fleet (Blockade & Transport Small craft.
4. Fourth Fleet (Mandate Defense Force) 1 Desron, 1 Subron and
many small units
5. Fifth Fleet ? ?
6. Sixth Fleet (Submarine Fleet) 6 Subrons
7. Carrier Fleet (Aircraft Carriers) 5 Cardivs
8. Combined Air (Seaplane tenders, etc.) 4 Airrons, & shore based
II. Japanese Naval Forces (Staff Headquarters) 1 PG and 3 DD s
1. First China Exped. (Central China) Gunboats
2. Second China (South China) 1 CA, 1 CL and small
Exped. Fleet. craft.
3. Third China (North China) Torpedo Boats, etc.
4. Southern Exped. (Saigon) 1 CL, transports and
Fleet. mine craft.
 The Japanese Navy now includes more vessels in active service than ever before. More merchant ships have been taken over by the Navy, and the line between merchant ship and naval auxiliary grows fainter all the time. The base forces and guard divisions in the Mandated Islands have also greatly increased the strength of the Navy, which is on full-war-time footing.
COMBINED FLEET AND FIRST FLEET
YAMAMOTO Isoroku, CinC (Admiral)
Batdiv One Desron One (Cont’d)
NAGATO (F) Desdiv 27
MUTSU SHIRATSUYU (F)
Batdiv Two YUGURE
FUSO (F) SHIGURE
ISE Desron Three
HYUGA SENDAI (F)
Batdiv Three Desdiv 11
HIYEI (F) FUBUKI (F)
*HARUNA Desdiv 12
Crudiv Six SHIRAKUMO (F)
KAKO (F) SHINONOME
KINUGASA Desdiv 19
Desron One ISONAMI (F)
ABUKUMA (F) SHIKINAMI
Desdiv 6 AYANAMI
IKAZUCHI (F) URANAMI
INAZUMA Desdiv 20
SAZANAMI AMAGIRI (F)
Desdiv 21 YUGIRI
NENOHI (F) ASAGIRI
HATSUHARU Total: 10 BB, 4 CA, 2 CL, 27 DD.
*Note: The HARUNA has been inactive during 1941, and is probably undergoing major repairs.
 COMBINED FLEET
Crudiv Four Desron Two (Cont’d)
TAKAO (F) Desdiv 16
Crudiv Five* TOKITSUKAZE:
MYOKO (F) Desdiv 18
Crudiv Seven KAGERO
KUMANO (F) SHIRANUHI
MOGAMI Desron Four
MIKUMA NAKA (F)
SUZUYA Desdiv 2
Crudiv Eight YUDACHI (F)
TONE (F) MURASAME
Desron Two SAMIDARE
JINTSU (F) Desdiv 9
Desdiv 8 ASAGUMO
ASASHIO (F) YAMAGUMO
MICHISHIO Desdiv 24
Desdiv 15 KAWAKAZE (F)
HAYASHIO Total: 13 CA, 2 CL, 28 DD.
*Note: There is a possibility that a new cruiser has been added to
 THIRD FLEET
TAKAHASHI Ibo-Vice Admiral
NORTHERN BLOCKADE FORCE 2nd BLOCKADE FORCE-Con.
CHOGEI (F) Desron Five
Subdiv ........ Desdiv 34
Subdiv ........ TACHIKAZE
........ 1st BASE FORCE
........ ........ Maru (F)
........ Minelayer Division
2nd BLOCKADE FORCE ITSUKUSHIMA
Desron Five AOTAKA
NATORI (F) HATSUTAKA
Desdiv 5 Mine Sweeper Division 1 and 21
ASAKAZE AM-1 AM-7
HARUKAZE AM-2 AM-8
MATSUKAZE AM-3 AM-9
HATAKAZE AM-4 AM-10
Desdiv 12 AM-5 AM-11
SATSUKI AM-6 AM-12
FUMITSUKI Gunboat Division 1
MINATSUKI 6 Gunboats (Converted Fishing
2nd BLOCKADE FORCE-Con. 2nd BASE FORCE
SUBCHASER SQUADRON ......... Maru, (F)
.......... (F) Minelayer Division 17
Subchaser Division 1 and 11 SHIRTAKA
PC-1 PC-7 YAEYAMA
PC-2 PC-8 KUNAJIRI
PC-3 PC-9 At least 5 other men of war, and 17
Subchaser Division 21 and 31 merchant ships.
PC-4 PC-10 Total: 1 CL, 12 DD, 1 AS, 6 SS, 6 CM,
PC-5 PC-11 12 AM, 6 XPG 12 PC, 46, AP.
27 AP-Names Unknown
 FOURTH FLEET
Crudiv Eighteen FOURTH DEFENSE FORCE (HQ-
TENRYU (F) TRUK
TATSUTA Miscellaneous Forces Ashore, in-
KASHIMA cluding Air Group #17 and
Desron Six Ponape Detachment of 4th Def.
YUBARI (F) Force, Kusaie Detachment of 4th
Desdiv 29 Def. Force, Olol Detachment of
OITE 4th Def. Force, Greenwich De-
HAYATE tachment 4th Def. Force, Mort-
ASANAGI lock Detachment 4th Def. Force,
YUNAGI Pingelap Detachment 4th Def.
Desdiv 36 Force, Puluwat Detachment 4th
MUTSUKI (F) Def. Force, Lamortek Detach-
KISARAGI ment ...... (Hall ?) of 4th Def.
MOCHITSUKI 5th BASE FORCE
Subron Seven Saipan, Headquarters
JINGEI SHOEI MARU (F)
Subdiv 26 Guard Division 5
RO-60 Composition unknown
RO-61 Minelayer Division 19
RO-62 OKINOSHIMA (F)
Subdiv 27 TOKIWA
RO-65 Subchaser Division 56
RO-66 KASHI (F)
RO-67 XPG 561 (?)
Subdiv 33 XPG 562 (?)
RO-63 XPG 563 (?)
RO-64 Gunboat Division 8
RO-68 Composition unknown
Subdiv----- 9 AP or AK
......... FIFTH DEFENSE FORCE (HQ-SAI-
......... Miscellaneous Forces Ashore, in-
8 XPG cluding Air Group #18.
4th BASE FORCE Tenian Detachment, 5th Defense
Truk, Headquarters Force
........ Maru (F) PAGAN Detachment, 5th Defense
Guard Division 4 Force
........ Maru (F) Survey and Patrol Division
........ KATSURIKI (CM)
4 AP or AK KOMABASHI (AS)
FIFTH DEFENSE FORCE Con. 6th BASE FORCE-Continued
Repair and Salvage Division Minesweeper Division 16
MATSUEI MARU NAGATA MARU (F)
NAGAURA (MARU) CHOKAI MARU
3rd BASE FORCE DAIDO MARU
Palao, Headquarters IKUTA MARU
.......... Maru (F) ?
Guard Division 3 |- (This may
.......... Maru ....... | be the
.......... ....... Maru | SALVAGE
.......... ....... Maru | Unit known
.......... ....... Maru | to be in
.......... | 6th Base
Subdiv 6 |- Force)
RO-56 Subchaser Division 5
Subchaser Division 55 SIXTH DEFENSE FORCE (HQ-
.......... Maru (F) JALUIT)
XPG 551 (?) KAIKEI Maru
XPG 552 (?) #5 FUKU Maru
XPG 553 (?) ....... Maru
XPG 554 (?) Miscellaneous Forces ashore in-
THIRD DEFENSE FORCE (HQ cluding AIR GROUP #19 at
PALOA) IMIEJI, Jaluit Atoll and prob-
Miscellaneous Forces Ashore, in- able Air Groups at WOTJE and
cluding Air Group #16 and TOBI KWAJALEIN and RUOTTO Is.
detachment of 4th Defense Force (Kwajalein Atoll) Detach-
..... Detach. 4th Def. Force ment 6th Defense Force KWA-
...... " " " " JALEIN Is. (Kwajalein Atoll),
...... " " " " TAROA Is. (Maloelap Atoll ),
...... " " " " ENIWETOK Is. (Eniwetok
...... " " " " Atoll), UJELANG Atoll, ENY-
Estimate these unknown loca- BOR Is. (Jaluit Atoll), IMIEJI
tions to be SOROI, HELEN Is. (Jaluit Atoll), WOTJE
REEF, ULITHI, YAP and AN- Atoll-Detach. of 6th Def. Force,
GUAR). UTIRIK Atoll-Detach. of 6th
6th BASE FORCE Def. Force.
Jaluit, Headquarters Total: 4 CL, 9 DD, 2 AS, 16 SS 1 Sur-
TAKUHAN MARU (F) vey Ship, 3 CM, 15 XPG, 3 PC, 4 XAM
41 AP or AK.
 FIFTH FLEET
The composition of a new Fifth Fleet is still unknown.
The Flagship has been reported at Maizuru.
Subron One Subron Two
TAIGEI (F) KITAGANI (F)
Subdiv I Subdiv 7
Subdiv 2 Subdiv 8
Subron Three Subron Six
NAGOYA MARU (F) KINU (F)
Subdiv 1 Subdiv 9
Subdiv 12 Subdiv 13
I-69 Subron Ten
I-70 KARASAKI (F)*
Subdiv 20 Subdiv 18
Subron Five Subdiv 19
YURA (F) I-56
Subdiv 28 I-57
I-60 Subdiv 21
Subdiv 29 RO-33
I-61 (Sank 10-2-41) RO-34
I-62 Total: 3 CL, 2 AS, 1 AP, 42 SS.
*Note: The old sub-tender KARASAKI appears to have been recommissioned.
 CARRIER FLEET (Cardivs)
CV KAGA Flagship
Cardiv 1 Cardiv 4
KAGA (F) SHOKANU
Desdiv 7 Desdiv 3
OBORO (F) HOKAZE
Cardiv 2 Cardiv ......
SORYU (F) CV KORYU
HIRYU CV KASUGA (MARU)
Desdiv 23 Total: 10 CV, 16 DD.
 COMBINED AIR FORCE
Kanoya Naval Air Station, Hdqtrs.
Shore-based land planes and seaplanes. The organization provides for great mobility. Air units are ordered to work with other forces, and return to the Combined Air Force pool when their mission is fulfilled. The named Air Groups (e. g. the Takao Air Group) are not tied down to their stations, but are sent freely wherever they are needed. Furthermore, the various air squadrons and air groups frequently split into smaller units, and are scattered over wide areas.
Because of this extreme mobility, the picture is constantly changing. Accordingly, the following list makes no attempt to indicate all the temporary groupings into which the various units may be combined.
SHIP-BASED SQUADRONS SHORE-BASED AIR GROUPS
Air Ron 6 8th Air Group
KAMIKAWA MARU (F) 10th Air Group
FUJIKAWA MARU 11th Air Group
KENJO MARU 12th Air Group
(Has been working with the 3rd 14th Air Group
Fleet) 16th Air Group
Air Ron 7 17th Air Group
CHITOSE (F) 18th Air Group
CHIYODA 19th Air Group
MIZUHO 23rd Air Group
(Has been working with the. 1st Chichijima
Air Ron 24 Genzan
KAMOI (F) Hyakurihara (or Moribara)
1 XAV Iwakuni
Yokohama Air Group Kanoya (Hdqtrs.)
Chitose Air Group Kashima
(Has been working with the 4th Kasumigaura Sasebo
Fleet) Kisarazu Suzuka
Patrol Squadron 2 Kure Takao
NOTORO Maizuru Tateyama
(Formerly with Air Ron 6) Oita Tsukuba
TOTAL: 5 AV, 3 XAV, 35 Air Groups.
 TRAIN FOR COMBINED FLEET
SHIRETOKO ONDO AKASHI
SATA HAYATOMO MUROTO
TSURUMI NARUTO OTOMARU
SHIRTYA MAMIYA SETTSU
Total: 8 AC, 1 AF, 2 AR, 1 AC, 1 Ice Breaker, 1 Target Ship.
 JAPANESE NAVAL FORCES IN CHINA
KOGA, Mineichi-Vice Admiral
SHANGHAI BASE FORCE Patrol Division 11-Continued
ASUGA KURI HIRA
TSUGA HASU TOBA
Shanghai Harbor Affairs Section ATAMI
Special Naval Landing Force, Shanghai FUTAMI
Nanking Base Force FUSHIMI
Special Naval Landing Force, Nanking SUMIDA
CENTRAL CHINA FLEET, OR FIRST Air Group 10
EXPEDITIONARY FLEET Hankow Base Force
Kiukiang Base Force
KOMATSU, Teruhisa-Vice Admiral Gunboat Division ? ?
UJI, Flagship SHINFUKU MARU (F)
Patrol Division 11 HITONOSE
SETA Total: 4 PG, 10 PR, 1 AP.
JAPANESE NAVAL FORCES IN CHINA-Continued
SOUTH CHINA FLEET, OR SECOND  NORTH CHINA FLEET, or
EXPEDITIONARY FLEET THIRD EXPEDITIONARY FLEET
SUGIYAWA, Rokozo, Vice Admiral
NIIMI, Wasaichi, Vice Admiral IWATE, Flagship
ISUZU, Flagship Patrol Division 12
Crudiv 15 IWATE (F)
ISUZU (F) MANRI MARU
ASHIGARA Torpedo Boat Division 11
Patrol Division 14 HATO
Torpedo Boat Division 1 Torpedo Boat Division 21
Guard Division 15 KARUKAYA
Guard Division 16 Gunboat Division 1
Canton Base Force Gunboat Division 2
Amoy Base Force Gunboat Division 13
Hainan Is. Base Force Gunboat Division 14
13 Special Service Ships Tsingtao Base Force
Total: 1 CA, 1 CL, 4 TB, 1 PG, 2 AM, SOUTHERN EXPEDITIONARY FORCE
13 Misc. KASHII (F) (CL)
Total: 1 OCA, 1 DD, 8 TB, 1 AP.
 (B) JAPANESE FORCES AND INSTALLATIONS IN THE MANDATED ISLANDS
1. FOURTH FLEET, which may be termed the MANDATE FLEET, apparently administers, the Naval activities, afloat and ashore and also the Army Garrisons units in the Mandated Islands. While the forces afloat exercise administrative jurisdiction over the Mandate area, the Yokosuka Naval District is directly responsible for the supply of stores, material and provisions. Truk is the headquarters for supply and munitions and has been principle Fourth Fleet operating base.
2. Up to the present the entire Mandated Islands have been lightly garrisoned, the majority of the garrison units being Naval Defense Forces ("special Landing Forces" corresponding to our Marine Corps) but some Army troops are believed to be on SAIPAN, PALAO, PONAPE, TRUK and JALUIT. The total garrison force has been estimated at fifteen thousand. In addition, there are Civil Engineering Units engaged in development work on various islands. Working in conjunction with these are naval engineering units, naval ordnance specialists, navy yard units with civilian navy yard workers and technicians. The network of naval radio stations has been greatly expanded, meteorological stations and high frequency direction finders installed at strategic locations, aviation facilities increased both in scope and number, and shore-batteries emplaced on strategic islands of key Atolls.
3. It is apparent that a decision to expedite the fortification, expansion of facilities and militarization of the Mandated Islands, was made late in 1940, probably concurrently with the signing of the Tripartite Pact. The movement of naval auxiliaries, small and medium cargo, freight-passenger vessels (ex-merchant marine) to the Mandates began in December, 1940, and has increased in scope and number until some seventy odd vessels are engaged in this traffic, the average number present in the Mandate area at any one time being some forty odd vessels.
4. The function of supply of munitions, supplies, material and provisions to the Mandates is under the YOKOSUKA Naval District with a Headquarters for Civil Engineering, Munitions, Military Stores and Supplies for the Mandates centered at Truk, although this function is normally under the jurisdiction of Yokosuka as the Mandates are in the First (HQ-YOKOSUKA) Naval District.
5. The Commanders of the 3rd, 4th, 5th, and 6th Base Forces are subordinate commanders under Commander-in-Chief, 4th Fleet; they have a designated Flag-
ship and a Headquarters or Administrative Section, the latter remaining ashore at the home base regardless of the movements of the command or the Flagship. Each Base Force contains a DEFENSE FORCE, detachments of which are stationed on outlying islands of that general area. Four Ro Class submarines have been reported to be attached to the PALAO BASE FORCE.
6. Considerable air activity has been in evidence in the SAIPAN PALAO-PELELIU, TRUK, PONAPE and JALUIT-KWAJALEIN areas. Close cooperation has been noted between the Defense Forces and the Aircraft activities at their home bases. Foreign steamers nearing the SAIPAN area have been subject to aircraft observation and close scrutiny by Patrol planes, Bombers and fighters. Heavy land plane bombers and Patrol planes, undoubtedly ORANGE, have made reconnaissance flights over the Gilbert Islands (TARAWA; BUTARI-TARI, and BERU).
7. The distribution of material, personnel, and installations in the Mandated Islands is indicated in table "A". While this is admittedly incomplete and may be subject to inaccuracies, it represents the latest and best intelligence on this subject. In addition to those listed in Table A, there are a number of potential bases, principally in the lagoons of the naturally protected atolls, which may be used as emergency bases or may be earmarked for "priority two" development.
8. The latest information (up to 25 November 1941) indicates that the present distribution of the Air forces (believed to be a temporary strategical disposition other than a permanent assignment) in the Mandates is:
Identification Location Includes
Airron 24 Marshall Area (AV) KAMOI
(AV) ...... Maru
ex-CHITOSE Air Group
ex-YOKOHAMA Air Group
11th Air Group PALAO Area
16th Air Group PALAO Area
17th Air Group TRUK
18th Air Group SAIPAN
19th Air Group IMIEJI Is. (Jaluit
Air Station (and Air Group?) WOTJE
Air Station (and Air Group?) KWAJALEIN
? AIR GROUP TRUK
The exact composition of these Air Groups is unknown and the estimates of total plane strength in the Mandates vary widely: 62-268 planes.
Last Page of Intelligence Bulletin No. 45-41.
(Pages 130, 131 132, and 133 of Exhibit B consist of Table A showing the distribution of Japanese material and personnel forces in the Mandates, a sketch of Palao, and a sketch of Malakal Harbor. These pages will be found reproduced as Items Nos. 2, 3, 4, and 5) EXHIBITS-ILLUSTRATIONS, Clausen Investigation. These illustrations will be found bound together following the printed exhibits of the Clausen investigation.)
 NOTES TO ACCOMPANY SKETCH OF JALUIT
1. Aviation facilities.-Two landing fields, each with a hangar capable of using twenty medium sized planes. Engineering Shop (camouflaged) situated between the two fields. Adjacent storehouses (galv. iron) camouflaged. Diesel fuel and gasoline storage in camouflaged, above-
ground tanks adjacent to air fields. Diesel power plant (June 1940). Eighty planes reported based here (November, 1940).
On beach opposite southern air field is Naval Air Station having small ramp and one hangar for seaplanes (June 1940). This may be an auxiliary as present indications point to naval air Base on IMIEJI (EMIDJ) Is.
2. Headquarters-Two story concrete building. Large building to SE of headquarters is Post Office and Telephone central. Flagstaff adjacent to Post Office is also used as signal tower. In town are many one story concrete stores. Good bituman and powdered coral roads.
3. Radio towers.-Two steel combination radio and lookout towers 400 feet high. Diesel engine power plant near southern tower (1940).
4. Shore Batteries-Bases and trunnions along the three quarter mile water-front street called the Marine Parade (1940) (guns not mounted in June, 1940 but are now). Also three 6" guns and a battery of four 4.7" field pieces. Barracks for regular garrison of 500 soldiers (1940) (probably enlarged now).
Mobile Batteries-Machine guns and AA guns mounted on Diesel-tractor towed trailers. 10 searchlights on pneumatic tired truck assemblies (1940).
5. Government Pier-600 feet long, 75 feet wide (18’-25’ alongside) equipped with two railroad tracks and three 10 ton mobile cranes. Storehouse on end of pier (1940).
6. Mole-150’ concrete mole constructed parallel to shore line along NW. corner of JABOR (1933).
7. Conspicuous red building (may be red-roofed building) (1936).
8. South Seas Trading Co. PIER (N. B. R. or "NAMBO") also called "SYDNEY Pier". Two water tanks and warehouses. Coal and briquette storage (1938).
9. Two buildings (resembling hangars) with tracks leading down to water from one of them (beaching gear?-small marine railway?). A gasoline storage located near the two buildings. (1936.)
(Page 135 of Exhibit B is a sketch of Jaluit Harbor which will be found
reproduced as Item No. 6, EXHIBITS-ILLUSTRATIONS, Clausen Investigation.
These illustrations will be found bound together following the printed
exhibits of the Clausen investigation.)
Page maintained by Larry W. Jewell, email@example.com. Created: 12/13/96 Updated: 12/19/96