Gunter Bernert, Discovery Divers, Coron 
 

HISTORY OF THE CORON BAY AIR RAID OF 24 SEPTEMBER 1944
By Capt. Peter Heimstaedt:

The following is a detailed and updated account on the famous air raid of U.S. naval aircraft on
Japanese shipping assembled in Coron Bay/Busuanga 22-24 Sep 1944. For further in-depth
research please refer to the bibliography listed in the addendum.

Furnished with records and narrative descriptions from Brian Homan and Roland Hanewald who
were among the first professional wreck divers in the Calamians, I started my research in 1992.
Thanks to the great support rendered by Gunter Bernert we both explored each known wreck to
the maximum extent aiming at identifying the ships which had succumbed to bombs and gunfire
50 years ago. I spent much of my leisure time at the "Bayside Lodge" in Coron with the drawing
of sketches of the wrecks. In Manila I went to the Philippine hydrographic institute NAMRIA
frequently to buy charts and ask for hydrographic statistics. I have had extensive communication
with Mr Teruaki Kawano, Head of the Military History Department of the National Institute for
Defense Studies in Tokyo. Again and again I had to express my gratitude for his indispensable
support. Back home in Germany, I studied Shizuo Fukui`s hand-made expert line drawings to
find out similarities of supply vessels of the Imperial Japanese Navy`s (IJN) Combined Fleet with
the wrecks on the bottom of Coron Bay.

Before having unveiled the mysteries of Olympia Maru and Taiei Maru which was achieved in
1997 I terminated the 4-year long project and continued my research in Subic Bay partly in
cooperation with Brian Homan. I probed the bottom of the sea at San Fernando (La Union) in
search of the last Japanese trooper to leave the Philippines in 1945. And I spent almost a week
at Santa Cruz (Zambales) to locate the heavy cruiser Kumano which sank near Hermana Mayor
Island in 1944. Then, in 1998 I helped Henny Smits to explore the two Samal Island wrecks in
front of the famous "Pearl Farm" beach resort in Mindanao. Today, I probably hold the most
complete documentation on WW II shipwrecks in the Philippines.

1. Prelude: Airgroups involved
The losses of the Imperial Japanese Navy (IJN) in the Calamian Group between 24 Sep and 9
Oct 1944 were caused by Airgroup 18, Airgroup 19 and Airgroup 31, three of the U.S. Navy`s
most successful carrier-based air wings in the Pacific theater. AG-18 was commissioned at
Alameda, Ca., on 20 July 1943. Originally, it was composed of 3 squadrons: Fighting 18 (VF-18),
Bombing 18 (VB-18) and Torpedo 18 (VT-18). In Sep 1943 VF-18 was detached. At Hilo (Hawaii)
in Feb 1944 VF-36 joined the Group and became VF-18, completing the Air Group`s
complement.

After 4 months of combat VF-18 was detached on 30 Nov 1944 at Ulithi. The remainder of the
Group returned to the U.S. reaching Alameda on 20 Dec 1944 for reforming.

AG-18 departed from Pearl Harbor on 15 Aug 1944 aboard U.S.S. Intrepid (CV-11), AG-31 on
U.S.S. Cabot (CVL-28). In company of U.S.S. Enterprise (CV-6) and various escorts they were
heading for the Palaus. Upon arrival on the scene northeast of the islands Intrepid and Cabot
joined the Task Group TG 38.2 while Enterprise reinforced TG 38.4. AG-19 was based on U.S.S.
Lexington (CV-16), flagship of Vice-Admiral Mitscher and crucial part of TG 38.3. Lexington had
been in combat for months and played a vital role in the Battle of the Philippine Sea (the famous
"Marianas Turkey Shoot") in June 1944.

The standard tactical organization was the Task Group (TG). Eventually, 2 CVs and 2 CVLs
operated with cruiser and destroyer escorts, but sometimes also with fast battleships. The Fast
Carrier Task Force was composed of 4 Task Groups under the overall command of a Vice
Admiral. Depending upon the fleet commander (Admiral Halsey with the 3rd fleet or Admiral
Spruance with the 5th fleet) the carrier striking arm was designated Task Force (TF) 38 or 58.
The designation changed whenever the fleet commander alternated for planning purposes. This
system allowed one team to conduct an operation while the other prepared for the next. It also
acted as a ploy to confuse the Japanese. When the Fast Carrier Task Force (TF-38/-58) was
instituted in Jan 1944, the commanding officer was Vice Admiral Marc A. Mitscher. He remained
in command, alternating the TF-38/-58 designation, until fall 1944.

2. Combat activities during Aug/Sep 1944
Arriving at Eniwetok Harbor on 24 Aug U.S.S. Bunker Hill (CV-17) joined TG 38.2. On 6 Sep
1944 AG-18 launched its first fighter sweep and strike against the enemy at Palau.
From that time through 30 Sep the followowing targets were hit:
- Davao, Mindanao
- Matina, Mintal + Dalaio Fields, near Davao, Mindanao
- Visayas: Leyte, Samar, Cebu, Negros
- Peleliu (Air Support)
- Anguar (Air Support)
- Luzon: Clark Airfield, Manila Bay, Subic Bay, San Fernando (La Union)
- Calamian Group: Coron Bay, Busuanga

3. Target: Coron Bay
On 23 Sep reports from Combat Air Patrol (CAP) missions revealed unusual enemy activities in
the Calamians, south-west of Mindoro. AG-18 and AG-19 received orders to equip 12 Curtiss
SB2C-3 "Helldiver" bombers each with wing tanks and to send them out on a fighter-bomber
attack on Japanese shipping in and around Coron Bay. They were to carry two 500-pound bombs
each. The "Helldivers" were the latest models already fitted with the APG-4 automatic low-level
bombing system. AG-31 was ordered to provide fighter escort. However, also some
"Hellcat"-fighters had been equipped with bombs. The sortie was to cover a chart distance of 350
miles from the carrierseast of Leyte to Coron Bay, thus, it became one of the longest bombing
missions in the history of U.S. naval aviation.

Just before dawn at 05:55 hrs. local time on 24 Sep 1944 Lexington, Intrepid and Cabot launched
following aircraft:
- VB-18 with 12 Curtiss SB2C-3 "Helldiver" bombers;
- VB-19 comprising 12 "Helldiver" bombers, 2 of which were forced to return due to engine trouble
and defective wing tank fuel supply; and ...
- VF-31 (the "MeatAxe Squadron - Cut `em down") with 12 Grumman F6F-3 "Hellcat" fighters.

All in all, 24 bombers and 96 fighters were ordered on this sweep by TF-38. According to the
"After Action Report" of VB-19 the number of fighters that actually participated from other Task
Groups is not known. Lt. (S.G.) Mark Zalick led AG 18`s bomber group VB-18, Commander R.
McGowan was leader of VB-19. After a 3-hour flight they surprised 15 Japanese ships in the
Bay, the Coron Passage, the area just west of Coron Island as well as 3 more vessels in a
remote anchorage at the northern coast of Busuanga. Ships ranged in size from small freighters
to 15,000 ton tankers.

Upon teaming up to take on the targets the Japanese ships were dispersed as follows (according
to AF-31`s "After Action Report" ):
i)  Bbetween Tangat and Lusong Islands:
- 1 x destroyer (DD) or destroyer escort (DE);
- 2 x 10,000 ts auxiliary supply ships (AK or AG);
- 2 x 5,000 ts aux. supply ships (AK or AG);
- 3 medium-sized aux. supply ships (AK or AG).
ii)  Between Lusong and Lajo Islands:
- 2 destroyers (DD);
- 1 auxiliary oiler (AO);
- 1 gunboat (PG).
iii)  West of Lajo Island:
- 2 destroyers (DD) or destroyer escorts (DE)
iv)  In Coron Passage:
- 1 x 7,000-8,000 ts aux. supply ship (AK or AG)
v)  West of Coron Island:
- 3 Subchasers (SC)
vi)  North of Busuanga Island::
- 1 x 10,000-12,000 ts aux. supply ship (AK or AG)
- 2 x 7,000-9,000 ts aux. supply ships (AK or AG)

4. Japanese plans and movements
Though COMTHIRD Fleet (i.e. Officer-in-command U.S. 3rd Fleet, Admiral William F. Halsey in
U.S.S.New Jersey) characterized the enemy`s non-aggressive attitude as "unbelievable and
fantastic", the Japanese were not surprised by the increasing American airborne strikes against
Japanese installations in the Philippines. In August 1944 the Imperial General Headquarters
(I.G.H.) had decided already that top priority in preparation for a "general decisive battle" along
the inner defense line must be assigned to the Philippines.

For the Imperial Japanese Navy, main value of the Philippines was for basing troops and staging
ships, especially supply vessels which were essential units in providing replenishment for capital
warships. However, main failure of the Combined Fleet`s command until September 1944 was to
concentrate oilers, provision ships, salvage vessels and other auxiliary units in just a few "hot
spots" in the Western Pacific. As "Operation Hailstorm" and the tragedy of Truk Lagoon in
February 1944 clearly revealed, the Japanese had not fully understood the importance of a
dispersed operating bases (DOB) policy.

It was only until the first American strikes on Palau in early September 1944 when Admiral
Toyoda, Commander-in-Chief (C-in-C) of the Combined Fleet, realized that a fleet of almost 40
supply vessels had been anchored in Manila Bay or moored in Manila harbor. When TF 38.2
started their strikes against enemy shipping around Luzon in the second week of September,
Manila harbor suffered severe damage, and numerous Japanese ships were sunk. Actually,
Vice-Admiral Mikawa, commander of the Southwest Area Force in Manila, was not responsible
for the supply vessels in Manila area due to the majority of the vessels operating under command
of the Army. However, he advised Field Marshall Terauchi, commander of the Japanese Southern
Army, that it would be recommended to transfer all
supply ships to Coron Bay which had served as a secure assembly place in the past. Terauchi
was reluctant to decide accordingly. When he finally gave orders on 21/22 September 1944 to
relocate the vessels he had sacrificed 15 ships which were bombed and sunk by repeated air
strikes from TF 38.

5. Japanese shipping at Busuanga Island
According to official Japanese and American sources following vessel movements are proven:

i)   Kogyo Maru:
(Aux. Supply Ship, IJN/Navy) After she had survived TF 38`s air attacks on Japanese shipping in
Manila Bay and Harbor on 21 Sep 1944 she received sailing order to transfer to Coron Bay and
weighed anchor at 1730 the same day. She arrived in Coron Bay on 23 Sep 1540 and dropped
anchor in position 11°58`54"N / 120°02`15"E (GPS). The night was spent in trying to camouflage
bridge and main deck. In the morning of 24 Sep at 0900 she was attacked by U.S. dive bombers.
After she had received several bomb hits the vessel sank with 39 men.

ii)  Okikawa Maru:
(Civilian oiler) She had been mistaken for more than 50 years to be a ship of very similar shape
and size named Taiei Maru. She was in Manila Bay during the said air attacks. The ship got
strafed but was only sligthly damaged. On 22 Sep she was ordered to move to Coron Bay and
set sail at 1500. The vessel arrived in Coron Bay on 23 Sep 1800 and dropped anchor near
Concepcion. At 0855 on 24 Sep the ship was attacked by 70 dive bombers. The first two or more
groups just strafed her and continued to head for the seaplane tender Akitsushima which
anchored a few cables to the West. At 0910 the bombers had scored numerous series of hits,
and the vessel began to sink. Three gunners and 5-6 sailors were dead. Rest of the crew
abandoned the ship. However, contrary to statements of Helldiver crew Bowie and Dietrich
(AG-31) Okikawa Maru did not sink at once. The forecastle remained afloat and burned until 9
Oct when another U.S. airgroup appeared and, in a final strike, send her to the bottom in position
12°01`10"N / 119°58`07"E (GPS).

iii) Olympia Maru
(Army cargo ship) Laden with 1,250 tons rice and 500 cbm supply materials for the Japanese
occupation forces in the Philippines she had suffered one direct bomb hit while in Manila Bay on
21 Sep. When (Japanese) Southern Army Command received air warnings on a second attack
the vessel was ordered to relocate to Coron Bay. She arrived on 23 Sep 1540 and dropped
anchor just West of Tangat Island. On 24 Sep around 0900 about 40 dive bombers took on
Olympia Maru after she had weighed anchor already and tried to evade the attacking planes. 10
aircraft attacked from starboard, then from port side. But it was not until the third wave when the
bombers scored direct hits to the engine room causing an explosion of the fuel tank at port side
(the vessel was Diesel-engined!). Fire spread over the engine room when another bomb went
through again. The engine stopped, another series of bombs hit the galley and cargo holds. At
1330 fire spread all over the ship bending the midship section. At 1426
the ship sank from the stern in position 11°58`21"N / 120°02`39"E (GPS). 14 crew members, 3
gunners and 2 passengers went down.

iv) Taiei Maru:
(Army cargo ship) Regretably, I still have no details on the history of this mysterious ship.
Kawano-san as well as Prof. Yamada have been requested to investigate, but to date they have
not found any clue that this vessel was actually in Coron Bay at the time of TF 38`s attack.
American sources still insist that two vessels with this name were sunk on 24 Sep 1944.

As I have found out, the oiler at Concepcion is not Taiei Maru but actually Okikawa Maru.  A
quite modern civilian tanker of 9,929 gross tons named Taiei Maru and very similar to the older
Okikawa Maru had been torpedoed already on 21 Aug 1944 by submarine USS Haddo in position
13°30`N/120°15`E. Just after dawn at 06:00 a.m. Haddo attacked a Japanese convoy, sank
Kinryu Maru (4,392 gt) and Norfolk Maru (6,576 gt) and topedoed Taiei Maru, but was unable to
observe sinking of the latter. It is obvious that even the Japanese were confused over the multiple
naming of their ships. Actually, the civilian oiler Taiei Maru never arrived in Manila. Therefore, it
seems that Haddo scored also this victim.
With regard to its dimensions and tonnage, I`m quite confident that the famous wreck lying on
her starboard side close to the pearl farm was the former freighter Taiei Maru! If I would be a dive
operator at Coron I would have already removed the encrustation at the stern where everybody
can see the letters "CEI...SH". This might be the name of the vessel before being captured by
Japanese troops. If somebody may reveal the entire name the Military History Dept. in Tokyo
may probably find out more about this ship.

By the way, it would be of interest that there are records on no less than six (6) vessels,
freighters and tankers which served for the Imperial Japanese Armed Forces under this name.
Whoever wishes to know each vessel`s fate, please let me know (web-contact@t-online.de).

As you can see on every dive the vessel suffered from a series of direct hits in the bridge
superstructure as well as into the hull. Obviously, she must have received some below-waterline
hits on her starboard side which caused a tremendous explosion of the engine-room which finally
led to her sinking. She lies in position 11°59`19"N / 120°02`08"E (GPS).

Moreover, Ekkai Maru ex-Morazan had been bombed and definitely sunk by TF 38 in Manila
harbor on 22 Sep 1944. The reason why many wanna-be`s and self-made researchers still
believe that Ekkai Maru was sunk in Coron Bay is very simple:

1. According to the JANAC list she was lost in Coron Bay. The JANAC list was issued in 1947
when Japan was still devastated and Japanese naval experts willing to assist the Americans
were not available. Most guys are using this source today as it is freely available, however, for
serious reserachers it has become obsolete and useless.
2. According to General Headquarters of the U.S. Military History Section she was sunk in
Manila on 22 Sep 1944. This source was published after meticulous evaluation of the Imperial
Japanese naval operations in WW II in 1952!

(Some British and Australian guys like Pete Gallo and Michael McFadyen are still spreading this
nonsense over the internet. I really hope that you may easily reconstruct your website in
accordance with the facts and figures given in this recap.)

v) IJNS Irako:
(Navy Provision Store Ship/Reefer) Allied type designator: AF
Irako had been underway from Japan to Takao (i.e. Kaohsiung/Taiwan today) when she was
damaged on 12 Aug 1944 by unknown cause. Carrying a deck load of reconnaissance water
planes she arrived in Coron Bay around 22 Sep 1944 and tried to hide her presence between
Tangat and Lusong Island. In the morning of 24 Sep a number of fighter bombers of Airgroup 31
expended their bombs on the vessel. Already by their first strike they scored direct hits into the
midship section. Set ablaze on the bridge superstructure Irako began to sink over the bow.
However, it took some time before she finally went down with considerable casualties. Her final
resting place is in position 11°58`10"N / 120°02`20"E (GPS).
(Nice photographs and expert line drawings available upon request.)

vi) IJNS Akitsushima:
(Navy Seaplane Tender) Allied type designator: AV
The vessel had suffered from minor damage inflicted by U.S. air attacks near Buka Isl. on 1 Sep
1942 and received two direct bomb hits during "Operation Hailstorm" in Truk Lagoon on 17 Feb
1944. However, she remained afloat due to her very strong construction and state-of-the-art
bulkhead design (just look at this point when diving the wreck next time). Criticism over the
relative long Japanese building times for special service vessels are, by the way, not justified. In
comparison, allied ships of similar purpose and design stood little chance to survive bombings
like these.

After being repaired in Japan she was back to service in July/August 1944. Akitsushima arrived
in Coron Bay almost at same time as Irako and anchored in the narrow sound separating Lajo
Isl. and Manglet Isl. Strafed by Lt. (J.G.) Tuaspern and his wing of AG-31 she was first mistaken
to be a destroyer escort (DE). VB-18 later scored one direct hit into the aft part of the vessel
causing a tremendous explosion most likley of the fuel tanks for the flying boat. She capsized
within a few minutes and sank in position 11°59`20"N / 119°58`15"E (GPS).
(Nice photographs and expert line drawings available upon request.)

vii) IJNS Kamoi:
(Navy Oiler / Special Seaplane Carrier) Allied type designator: AO
Her previous history is still not known well enough. It seems that she arrived in Coron Bay in
company of IJNS Akitsushima and anchored close to Lusong Isl. On 24 Sep 1944 she got
bombed by Airgroup 31. After being hit on the forecastle by Bowie and Dietrich (VF-31) she
caught fire, but managed to escape by steaming southward. Seriously damaged and crippled the
vessel reached the open sea without being hit again. Steaming at dead slow speed she was
torpedoed on 27 Sep by a U.S. submarine about 240 naut. miles south-west of Manila. Upon
arrival at Hong Kong (on ? Oct 1944) she was docked to undergo extensive repairs. There she
was bombed repeatedly by U.S. naval aircraft on 5 and 7 April 1945 and finally ran aground.
(Nice photographs and expert line drawings available upon request.)

viii) Unidentified Supply Ships (2):
According to the "After Action Report" of VF-31 there were two (2) other auxiliary supply ships in
Coron Bay area at the time of the attack. One was a ship of 4-5,000 gross tons at anchor just
West of Lajo Isl., the other was a vessel of 7-8,000 gross tons in the Coron Passage between
Busuanga and uninhabited Coron Isl. heading eastward. The latter remained untouched while the
other got strafed by Anderson-Duggin and McLaughlin-Arnold from VF-31 and was set aflame
from stern to bow. As stated in the report she was believed sunk. It would be useful to make test
dives at the western tip of Lajo Isl. to find out whether another big ship lies there on the bottom or
not.

ix) Kyokuzan Maru:
(Army Cargo Ship) She was anchored near a small uninhabitated island called Dimalanta at the
north coast of Busuanga with another 2 cargo ships lying abreast. As VB-19 was a couple of
minutes behind the other Airgroups, attacks had already begun over Coron Bay when they
reached the north-eastern shore of Busuanga at 09:00 hrs. The leader of the entire strike force
(Commander Ellis of AG-18?) ordered VB-19 to attack the targets in the northern area.
Unfortunately, the pilots were not allowed to drop their wing tanks which it was "believed
considerably affected the accuracy of the bombing". Out of 10 planes attacking the Japanese
ships 8 lost one wing tank during the dives. Main target was, of course, the single stack 10,000
ts-AK which is believed to be Kyokuzan Maru. According to the "After Action Report" of VB-19
Lt. (J.G.) L. R. Swanson scored a direct hit upon her port side, and "three or more very near
misses on this ship" from other planes were noted. As a result, the ship was set aflame on port
side near her living quarters.  However, it is obvious that vessel did not sink due to the bombing
as hull, cargo holds as well as engine room are still intact and lifeboat davits have been swung
out (note this point during your next dive). It is believed that her crew scuttled and abandoned the
ship lateron.
The position of the wreck is in 12°09`58"N / 120°09`19"E (GPS).
One of the other two cargo ships received a very near miss and got strafed thereafter. A small fire
broke out, however, it is believed that both remained afloat and managed to escape.

x)  Unidentified Submarine Chasers (3) and Gun Boat (1):
When VF-31 teamed up to sink the Japanese ships in Coron Bay there were also three (3)
subchasers (SCS) patrolling West of Coron Isl. They were strafed by Kona-Free-Zimmerman as
well as another unidentified plane. Consequently, two of them sank. One might be the so-called
"Skeleton Wreck" lying in shallow water at Balolo Point. The other was either never located or
she was likely able to creep to Tangat Isl. where she finally ran aground in the passage between
Tangat and Apo Isl. (see "East Tangat Wreck").

One gunboat was strafed by Wilson when cruising close to Concepcion village. Disabled by
hundreds of machine-gun bullets she was caused to beach herself at the Southern tip of Lusong
Isl. (see "Lusong Wreck").

xi) Nanshin Maru No. 27:
(Civilian tanker / 834 gt.) The so-called "Black Island Wreck" can be easily identified as a small
tanker converted to carry specific fuel (gasoline, Diesel, lube oil etc.) in small isolated tanks for
replenishment of land-based depots. It is in fact of certain interest that there were more than 30
identical vessels of the Nanshin Maru-type in operation for the Imperial Japanese Navy. These
coastal tankers were not much conspicuous, quite slow and unarmed. However, due to their
cargo they were vulnerable even to machine-gun fire from attacking aircraft.
According to U.S. sources Nanshin Maru No. 27 travelled in company of Nanshin Maru No. 25,
Nanshin Maru No. 3 as well as another vessel named barely Nanshin (53 gt.) which might have
been some sort of tug boat. The submarine U.S.S. Guitarro attacked the small convoy on 27 Aug
1944 just 5-8 nautical miles north of Calawit Isl. (Busanga) sinking Nanshin Maru No. 25 in
position 12°21N/119°55E. On the other vessels only medium damage was inflicted. It is
assumed that the submarine attacked the Japanese vessels by her guns as torpedoes were too
expensive to be wasted for minor enemy supply ships. Nanshin Maru No. 27 then continued to
proceed to Busuanga and entered Illulucut Bay south of Calawit Isl. where she was probably
anchored and repaired. It is reported that she sank on 13 Sep 1944 at the mouth of the Bay by
unknown cause. However, I dived in that area in 1994 but found no debris. Obviously, the vessel
was given up and drifted in the tidal current towards Malahon Isl. ("Black Island") where she ran
aground and finally sank in position 12°09`22"N/119°49`05"E (GPS).

6. Biodata and specifications of Japanese vessels at Coron Bay (not complete)

Important note: As usual, warships are measured by their standard displacement (stdd.)
in longtons, i.e. 1 tonne = 1,016 kgs. Merchant vessels are measured either by their
gross tonnage which is not a weight measurement but a cubic factor (1 gt. = 2.83 cbm)
or by their loading capacity in deadweight tons (tdw.). As American as well as Japanese
military sources do not mention this discrepancy, it is, therefore, assumed that sizes of
warships are given in displacement tons and tonnage of merchant ships are indicated
by gross tons.

i)   IJNS Akitsushima:
Type: Seaplane tender (AV); Jap. " Suijoki Bokan", Jap. type designator: As
Length over all = 118 m; Lpp = 113 m
Breadth = 15.7 m
Displacement = 4,724 ts stdd.
Propulsion = 4 x 2,000 shp geared Diesel engines, 2 shafts/2 screws/2 rudders
Max. speed = 19.0 knots
Range of operation = 4,000 naut. miles at 14.0 knots
Armament = 4 x 4.7"/50 cal. (12 cm) high angle guns in twin turrets; 10 x 1.0" (2.5 cm) AA guns
in twin mountings
Yard = Kawasaki Heavy Industries Co., Kobe/Japan
Built = 1940/41; launched = 25 Apr 1941; commissioned = 29 Apr 1942

ii)  IJNS Irako:
Type: Provision Store Ship/Reefer (AF); Jap. "Kyuryo-kan", Jap. type designator: Tp
Length over all = 146.9 m; Lpp = 143.3 m
Breadth = 19.05 m
Draft = 5.94 m (unloaded); 6.05 m (at stdd.)
Displacement = 9,570 ts stdd. / 11,100 ts max.
Propulsion = 2 x 4,150 shp geared steam turbines, 6 Kampon-type waterpipe boilers,
oil + coal fired; 2 shafts/2 screws/1 rudder
Max. speed = 17.5 knots
Range of operation = 6,600 naut. miles at 14.0 knots
Armament = 2 x 4.7"/50 cal. (12 cm) high angle guns in single armored stands;
5 x 1.0" (2.5 cm) AA guns in single stands; numerous depth charges in poopdeck racks
Yard = Kawasaki Heavy Industries Co., Kobe/Japan
Built = May 1940 until Feb 1941; launched = 14 Feb 1941; commissioned = 5 Dec 1941

IJNS Irako was ordered as a Special Service Ship (Jap. "Tokumu-kan") under the third 1937
supplementary program. The ship got fitted with powerful reefer installations, various shops for
confectionery and others and was commissioned as a "Large Fleet Reefer Supply Ship".

iii) Kogyo Maru:
Type: Navy Auxiliary Supply Ship (AG), Jap. "Yuso-sen"
Length over all = 129.07 m; Lpp = 128.0 m
Breadth = 18.0 m
Draft = 8.05 m
Gross tonnage = 6,353 gt.
Propulsion = 2 x 1.950 shp geared steam turbines from Ishikawajima Shipbuilding + Engineering
Co., Ltd.; 4 waterpipe boilers, oil fired; 1 shaft/1 screw/1 rudder
Max. speed = 15.8 knots
Range of operation = ?
Armament = 2 x 3 - 1.0" (2.5 cm) AA guns on top of bridge deck + 2 x 1 - 1.0" AA guns on
circular stands on forecastle and poop deck
Yard = Uraga Dock Co., Ltd., Uraga
Built = 13 Feb 1927 for Okada Gumi Kisen Kaisha, Osaka (int`l call sign: JZEM)
Converted = 13 Oct 1931 and 13 May 1941

iv)  Olympia Maru:
Type: Army Auxiliary Supply Ship (AG), Jap. "Yuso-sen"
Length over all = 128.01 m
Breadth = 16.76 m
Draft = 7.80 m
Gross tonnage = 5,612 gt.
Propulsion = 1 x 2,705 shp direct Diesel engine; 1 shaft/1 screw/1 rudder
Max. speed = 13.65 knots
Range of operation = ?
Armament = 2 x 1 - 1.0" (2.5 cm) AA guns in special stands on forecastle + poop deck
Yard = Mitsubishi Heavy Industrial Co., Kobe (?)
Built = 2 Jan 1920 launched for Mitsubishi Kisen Kaisha
Converted = 2 Jun - 2 Aug 1930 from steam to Diesel engine by ? yard

v)  Kyokuzan Maru:
Type: Army Auxiliary Supply Ship (AG), Jap. "Yuso-sen"
Length over all = 135.90 m; Lpp = 128.0 m
Breadth = 17.8 m
Draft = 7.80 m
Gross tonnage = 6,492 gt.
Propulsion = 1 x 3,882 shp geared turbine; 1 shaft/1 screw/1 rudder
Max. speed = 15.06 knots
Range of operation = ?
Armament = 3 x 1 - 1.0" (2.5 cm) AA guns in special athwardship stand on forecastle + circular
stand on poop deck
Yard = ?
Built = 18 Mar ???
Int`l call sign = JLXP

vi)  Okikawa Maru:
Type: Navy Auxiliary Oiler (AO), Jap. "Juyu-sen"
Length over all = 160.51 m; Lpp = 153.0 m
Breadth = 20.0 m
Draft = 9.18 m
Gross tonnage = 10,043 gt.
Propulsion = 1 x 8,600 shp direct triple expansion steam engine; 1 shaft/1 screw/1 rudder
Max. speed = 18.5 knots (?), in other records: 13.5 knots
Range of operation = ?
Armament = 2 x 1 - 1.0" (2.5 cm) AA gun in special stand on poop deck
Yard = ?
Built = 1926 - 1930; launched = 18 Mar 1930; completed = 18 Oct 1931
Type = ITL-1 crude oil tanker
Special installations = Hose reel on portside bow section for fuel supply to other ships at sea.
(Replenishment at Sea/RAS was not much developed in the Imperial Japanese Navy as it had
been in the American, British and German Navies. In general, there was only one procedure in
the IJN applied to replenish capital warships: the fore-and-aft method meaning that the fuel hose
was released from the bow of the oiller and then picked up by the vessel to be replenished.)

vii) Aux. Subchaser / Aux. Patrol Boat:
Allied type designators: SCS / PG
Jap. "Kusen Tokumu-tei"; type designator: aCh
Jap. "Shokai Tokumu-tei"; type designator: aP
Details not yet available; will keep on investigating.
 

7. Conversion table for Japanese Showa calendar into Gregorian calendar figures

           Showa 1 =
                  1926
                                            Showa 11 =
                                                     1936
           Showa 2 =
                  1927
                                            Showa 12 =
                                                     1937
           Showa 3 =
                  1928
                                            Showa 13 =
                                                     1938
           Showa 4 =
                  1929
                                            Showa 14 =
                                                     1939
           Showa 5 =
                  1930
                                            Showa 15 =
                                                     1940
           Showa 6 =
                  1931
                                            Showa 16 =
                                                     1941
           Showa 7 =
                  1932
                                            Showa 17 =
                                                     1942
           Showa 8 =
                  1933
                                            Showa 18 =
                                                     1943
           Showa 9 =
                  1934
                                            Showa 19 =
                                                     1944
          Showa 10 =
                  1935
                                            Showa 20 =
                                                     1945
 

7. Bibliography

1. American Sources
Alden, John D.: "U.S. Submarine Attacks during WW II including Allied Submarine Attacks in the Pacific
Theater", U.S. Naval Institute, Annapolis, 1989

Belote, James H. and William M.:
"Titans of the Seas - Development + Operations of Japanese + American Fast Carrier Forces" (1975)

Craven, Wesley F. and Cote, James L. (editors):
"Army Air Forces in World War II - The Pacific: Guadalcanal to Saipan 1942-1944"

Dull, Paul: "A Battle History of the Imperial Japanese Navy" (1988)

Falk, Stanley: "Decision at Leyte" (1966)

Field, James A.: "Japanese at Leyte Gulf" (1947)

Jane`s: "Jane`s Fighting Ships 1942", 1942

Lawson, Robert L. (Editor):
"The History of U.S. Naval Air Power", The Military Press, New York, Aerospace Publishing Ltd.,
London, 1985

Morison, Samuel Eliot: "History of United States Naval Operations in World War II"
Vol. VIII: "New Guinea and the Marianas", 1st edition 1-1956
ISBN 0-316-58308-1
Vol. XII: "Leyte Gulf 1944-45", 1st edition 1-1958
ISBN 0-316-58317-0
Vol. XIII: "Liberation of the Philippines  1944-1945", 1st edition 1-1959
ISBN 0-316-58313-8
Vol. XIV: "Victory in the Pacific", 1st edition 1-1960
ISBN 0-316-58314-6
all: Little, Brown and Company, Boston, 1969

Odgers, George: "Air War against Japan 1943-45" (1957)

Reynolds, Clark G.: "Fast Carriers: Forging of an Air Navy" (1968)

Spector, Ronald H. "Eagle against the Sun"

"Thomas Jefferson Memorial Library", Makati, Metro Manila / Philippinen

U.S.-Navy: "The Imperial Japanese Navy in World War II - A Graphic Presentation of the Japanese
Organization and List of Combatant and Non-Combatant Vessels Lost or Damaged in the War"
Military History Section, Special Staff, General Headquarters, Far East Command, February 1952

U.S. Navy: "Japanese Naval and Merchant Shipping Losses during WW II"
Joint Army-Navy Assessment Committee (JANAC), U.S. Government Printing House, Washington D.C.,
February 1947

Watts, A. J. and Gordon, B. G.: "The Imperial Japanese Navy"

Woodward, C. Vann: "Battle for Leyte Gulf" (1947)

2. British sources
Guildhall Library, London:
- "Register of Shipping", 1938, 1940
- "Mercantile Navy List", 1940
- "Record of American and Foreign Shipping", 1940
- "Lloyd`s War Losses 1st and 2nd World Wars", Ref.section R910/45

3. German sources

Jentschura, Hansgeorg; Jung, Dieter; Mickel, Peter:
"Warships of the Imperial Japanese Navy, 1869-1945", published by United States Naval Inst.
Nov 1976, ISBN: 087021893X

4. Japanese sources

Beilstein, Christian W. (editor):
"Japanese Naval Vessels at the End of World War II", compiled by Shizuo Fukui, London 1991, ISBN
1-85367-125-8 (originally published in Japan by the Administrative Division, 2nd Demobilization Bureau,
on 25 Apr 1947

Imperial Japanese Navy Department: "Kaijôhogoyôsenmeibo" (List of the Ships for Convoy)

"Senji Senpakushi" (History of the Merchant Ship in Wartime)
"Rengokantai Gunkan Meimeiden" (Ship History of the Combined Fleet)
"The Maru Special, Japanese Naval Vessels, No. 25, 1979"

Ministry of Welfare: "Sônan Senpaku Meibo" (List of the Wrecked Ships)

Hokaku Shinkenrei Kenkyûkai:
"Nihon Kaijô Hokaku Sinken Reishû" (Example of the Japanese Prize Ships Examination)
 

+++End+++

(subject to change due to further research)

Any kind of contribution, opinion, comment and/or amendment is welcome.
 

Shipwreck Discovery + Research Projects (SDRP)

Capt. Peter Heimstaedt

Falterweg 2, Rethorn
D-27777 Ganderkesee / Germany
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