Stories and Battle Histories of the Imperial Army's (IJA) Tankers


By Bob Hackett

with Erich Muethlhaler, Peter Cundall and Gilbert Casse

Discussion & Questions

Left-Map of N Sumatara Showing Pangkalan Brandan, Pangkalan Susu, Medan and Belawan
Right-Map Showing Palembang, Medan, Bangka in Sumatara and nearby Malaya (Malaysia)

Captured Dutch Oil Refineries and Storage Centers

The IJA operated the former Royal Dutch Shell oil refinery at Pangkalan Brandan in northern Sumatra. The oil was transported from port facilities at nearby Pangkalan Susu directly to Singapore, Malaya and other locations in the region on captured vessels such as BUKUM MARU (ex-Dutch ANASTASIA), ARARE MARU (ex-Dutch PAULA) and others.

The center of oil production in Sumatra was at Prabumulih, about 43 miles from Palembang, now the second-largest city in Sumatra, after Medan. Crude was transported via pipelines to the largest oil refineries in Southeast Asia - the former Royal Dutch Shell refineries at Pladju (Pladjoe), a few miles north of Palembang, captured intact in Feb '42 by the Japanese 2nd Parachute Regiment, and at Sungei (Soengai) Gerong, east of the city. Together, these two IJA operated refineries with a reported annual capacity of 20,460,000 barrels of crude were capable of producing 78 per cent of Japan's aviation gasoline and 22 per cent of its fuel oil.

The IJA used mostly smaller captured British and Dutch tankers to transport fuel across the Musi (Moesi) River. The Musi joins the Ogan and Komering rivers near Palembang. Below Palembang, the Musi is deep enough for ocean vessels and about 50 miles north it enters Bangka Strait.

Japan’s wartime demands for fuel were so great that almost daily trips were needed to transport the oil from Sumatra to Singapore for shipment to Empire and other distant destinations aboard large tankers such as OTOWASAN MARU. Fuel also was transported either in bulk or by case (tins) to the smaller more remote locations in and around Malaya and the former Dutch East Indies.

Asiatic Petroleum, a subsidiary of Royal Dutch Shell Oil, formerly owned storage centers at Pulau Bukum and Pulau Sebarok near Singapore. Refined product was brought from Sumatra and stored in these captured storage centers near Singapore. As the TROMS attached to this page will show, round trips from Palembang to Singapore and back, including loading and discharging fuel, averaged about a week, but many trips were longer, indicating possible loading and unloading difficulties and/or ships' engine troubles and perhaps groundings.

The remote location of the captured refineries in Sumatra permits their operation by the Japanese with impunity from Allied attack until the Combined Chiefs of Staff meeting at Cairo, Egypt in November 1943. The Cairo Conference (codename “SEXTANT”) is attended by President Franklin D. Roosevelt of the United States, Prime Minister Winston S. Churchill of the United Kingdom, and Generalissimo Chiang Kai-shek of the Nationalist Republic of China and the British and American Combined Chiefs of Staff. The purpose of the meeting is to address future military operations against Japan. One of the important agreements made is to inititate very long range range (VLR) bombing of vital targets in the Netherlands East Indies in 1944.

Left (British) from front: Unknown, General Hastings Ismay, Admiral of the Feet Andrew B. Cunningham, General Alan Brooke, Air Marshal Charles Portal, General John Dill, and unknown. Right (American) from front: Admiral Ernest J. King, Admiral William D. Leahy, unknown, General George C. Marshall and General Henry H. Arnold.

On the night of 10/11 August 1944, the USAAF launches "Operation Boomerang." Fifty-four Boeing B-29 "Super Fortress” heavy bombers of the Twentieth Bomber Command’s 358th (Very Heavy) Bomb Wing at Chengtu, China stage through the newly completed 7,200-foot strip at RAF China Bay, Ceylon to make a night radar attack on the Pladjoe refinery at Palembang, the first since its capture. A dozen planes fail for various reasons to reach the target, but 39 reach their primary targets, two bomb the secondary target of Pangkalan Brandan refinery, one an airdrome at Djambi and 8 mine the Musi River, through which all of Palembang's exports are shipped. Only 9 of the 444th Bomb Group's B-29's reach Palembang and are forced to bomb through heavy overcast. They drop 36 five-hundred pound GP bombs and 16 photo flash bombs. The results at Pladjoe are unobserved, but later deemed poor. The 462nd Bomb Group's 8 minelaying B-29s have better luck. Dipping under the 1,000-foot ceiling to only 500 feet above the Musi River, they strafe Japanese ships and sow 16 mines - the first such use of B-29s. The "Hellbirds" claim three ships sunk and damage to two more and close the approach to the refinery for a month.The 3,855 air mile, 19 hour 40 minute flight from Ceylon to Palembang (4,030 to the Musi) and back are the longest single-stage flights made by USAAF combat aircraft in WW II.

On 20 November 1944, Rear Admiral (later Admiral of the Fleet/Sir) Philip Vian’s British Task Force 67 launches Operation "Robson", the first of a series of attacks on oil installations in Sumatra collectively known as Operation “ Outflank”. "Robson" is an unsuccessful air strike on the Pangkalan Brandan refinery by carriers HMS INDOMITABLE and HMS ILLUSTRIOUS escorted by light cruisers HMS ARGONAUT, HMS BLACK PRINCE and HMS NEWCASTLE screened by destroyers HMS KEMPENFELT, HMS WAKEFUL, HMS WESSEX, HMS WHIRLWIND and HMS WRANGLER. 28 Grumman “Avengers”, 16 Grumman“Hellcats” and 16 Chance-Vought “Corsairs” attempt to attack the refinery, but because of bad weather over Pangkalan Brandan have to divert to the secondary target’s oil refineries, railway and harbor installations at Belewan Deli, Sumatra.

On 4 January 1945, Rear Admiral Vian’s Task Force 63 launches Operation "Lentil", a successful air strike on the Pangkalan Brandan refinery by carriers HMS INDOMITABLE, HMS VICTORIOUS and HMS INDEFATIGABLE escorted by light cruisers HMS SUFFOLK, HMS CEYLON, HMS ARGONAUT and HMS BLACK PRINCE and the 25th Destroyer Flotilla's HMS GRENVILLE, HMS UNDAUNTED, HMS URANIA, HMS URSA and HMS UNDINE and the Destroyer 27th Flotilla's HMS KEMPENFELT, HMS WHELP and HMS WAGER. The carriers launch 92 “Avenger” and Fairey “Firefly” bombers escorted by “Hellcat” and “Corsair” fighters. Sixteen fighters attack the nearby airfields and 32 “Avengers” and 12 rocket-firing “Firefy” fighter-bombers escorted by 12 fighters bomb the refinery. Two aircraft are lost, but the crews are rescued. The fighters shoot down two Japanese aircraft and destroy seven others on the ground. Heavy damage is inflicted on the refinery, oil storage tanks and a small tanker is set on fire, and two locomotives are hit. Seven enemy aircraft are also shot down by the escorting fighters.

At 0600, on 24 January 1945, Rear Admiral Vian’s Task Force 63 returns to Sumatran waters, this time off Palembang and launches Operation "Meridian One", a successful air strike on the refinery at Pladjoe. Forty-seven "Avenger" bombers, 10 "Firefly" fighter-bombers and 48 "Hellcat", "Corsair" and Supermarine "Seafire" fighters attack and badly damage the Pladjoe refinery while 24 fighters make a sweep over the airfield. The striking force is intercepted some miles short of the refinery and meets considerable fighter opposition and anti-aircraft fire. Fourteen Japanese aircraft are shot down and six are probable kills; 34 are destroyed and 25 damaged on the ground. Seven aircraft fail to return to their carriers.

On 29 January 1945, Rear Admiral Vian’s Task Force 63 returns off Palembang and launches Operation "Meridian Two", the target this time being the Sungei Gerong refinery on the opposite side of Musi River from the refinery at Pladjoe. Forty-eight "Avenger" bombers, 12 "Firefly" fighter-bombers with rockets and 40 "Hellcat", "Corsair " and "Seafire" fighters attack and badly damage the Pladjoe refinery while 24 fighters again sweep the airfields at Lembak and Tanglangbetoetoe. Important sections of the refinery including the cracking plant and power-house areas are wrecked by direct hits. Seven Japanese aircraft are shot down and three probably destroyed. Nine carrier aircraft are lost, but the crews of eight are rescued. A group of twelve Japanese bombers attempt an attack on the carriers during landing operations, but the attack is broken up by fighters, which shot down seven.

The two attacks on Palembang are the largest strikes by the Royal Navy's Fleet Air Arm during World War II. After the attacks, the refineries are completely out of action for two months and remain at a much reduced capacity for the remainder of the war.

During the war the Japanese employment of merchants ships was divided into three main administrative categories:
A = requisitioned and operated by the Japanese Army
B = requisitioned and operated by the Japanese Navy with civilian crew (captain often being Navy Reserve)
C = controlled and operated by the Senpaku Un´eikai (Civilian Shipping Administration)
X = requisitioned by the IJN and converted into armed Naval Auxiliaries with IJN crews (gunboats, minesweepers, etc.)

Beside the above categories, there were many shared employments Army/Civilian (A/C) and Navy/Civilian (B/C). These ships were called Haitosen. Normally, this meant that the vessel on its outbound journey was under Army or Navy control carrying troops, military supplies, etc. and on its return voyage was carrying cargo for the benefit of the civilian owner of ship.

While used by the Army, the Haitosen also received Army transport numbers like Army requisitioned vessels (A). Employments by Army or Navy could also be expanded, meaning that the ship was used by Army/Navy for one full turn (outward and homeward voyage) or even a series of voyages.

The majority of the IJA's tankers were salvaged British and Dutch ships and were part of the more than 2,000 foreign ships seized/raised by the Japanese. Their operation was contracted to civilian shipping companies. Several civilian tankers also were requisitioned by the IJA. There were also about 100 tankers, requisitioned by the Japanese Government's Senpaku Uneikai civilian wartime shipping authority, manned by civilian crews and shared with the Imperial Army. Those above 1,000 tons are listed below:

Tabular Records of Movement (TROMs):
Civilian Tankers in Imperial Army Service
(Classes link to specifications summaries)


Otowasan Maru
(revised 1/14/2013)


(posteded 5/4/2013)

Kaisoku Maru

No. 1 Class

Ogura Maru No. 1
(revised 1/14/2013)


Eiyo Maru
(revised 1/14/2013)


Tachibana Maru
(revised 1/14/2013))


Rikko Maru


Hokki Maru


Kyodo Maru


Teikon Maru
(ex-German Winnetou)

(revised 1/14/2013)


Nichinan Maru
(revised 1/14/2013)


Hakko Maru
(revised 1/14/2013)


Palembang Maru
(revised 1/14/2013)

Civilian Shipping Authority (Senpaku Uneikai) Requisitioned Tankers
Shared with the Imperial Army
(Classes link to specifications summaries)


Ariake Maru (revised 1/14/2013)

Ichiyo Maru (revised 1/14/2013)
Kokuei Maru (revised 1/14/2013)
Medan Maru (revised 1/14/2013)
Nanei Maru (revised 1/14/2013)
Nichinan Maru No. 2 (revised 2/12/2012)
Nichirin Maru (revised 1/14/2013)
Ogurasan Maru (revised 1/14/2013)
Otorisan Maru (revised 1/14/2013)
Sarawak Maru (revised 1/14/2013)
Seishin Maru (revised 1/14/2013)
Shincho Maru (revised 1/14/2013)
Shinei Maru (revised 1/14/2013)
Tenshin Maru (revised 1/14/2013)
Yamamizu Maru No. 2 (revised 1/14/2013)
Zuiho Maru (revised 1/14/2013)
2TM Class

Ceram Maru

Captured and Foreign Tankers in Imperial Army Service
(Ex-Countries link to specifications summaries)

Ex-British Vessels

Honan Maru (ex-War Sirdar)
Nansei Maru (ex-Pleiodon)
Shosei Maru (ex-Solen)

Ex-Dutch Vessels

Arare Maru (ex-Paula)
Bukum Maru (ex-Anastasia)
Gyoryu Maru (ex-Sumatra)
Kikusui Maru (ex-Iris)
Yuno Maru (ex-Juno)

Bibliography of Sources

About the Authors

Bob Hackett is a military historian and researcher. Retired from the United States Air Force and later from the aerospace industry, he resides in the United States.

Erich Muethlhaler is a maritime historian and researcher He resides in Germany.

Peter Cundall is a maritime historian and researcher who specializes in merchant ships. He resides in Australia.

Gilbert Casse is a maritime historian and researcher. Retired from aerospace industry and later from managing Le Mans racing cars and drivers. He resides on the SW coast of France.

Questions to the authors concerning these TROMs should be posted on the Discussion and Questions board.