(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
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
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
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
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
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
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.)