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  Azumasan Maru (Deep Ruinin Wreck)
Troop Transport

7,623 Tons

Click For Enlargement
USN October 16, 1942
Ship History
Built by Mitsui Bussan K.K. Zosensho at Tama. Laid down November 18, 1932 as a 7,613 ton refrigerated cargo ship. Launched May 28, 1933 as Azumasan Maru. Completed July 31, 1933 for Mitsui Bussan K.K. and registered in Kobe.

During August 1933 departs Yokohama on the Mitsui Bussan commercial route via Penang and Singapore and New York. On October 6, 1937 arrives Yokosuka. On December 5, 1938 arrives Manila. On June 13, 1939 arrives San Francisco.

Wartime History
On October 15, 1941 arrives Sakurajima for conversion by Osaka Iron Works Shipyard into an auxiliary transport. On November 20, 1941 registered with the Imperial Japanese Navy (IJN) as an auxiliary transport (Ko) with a Japanese Navy captain attached to the Maizuru Naval District and based at Maizuru.

On December 10, 1941 departs Osaka with Goyo Maru and the next day arrives Yokosuka. On December 14, 1941 to Shibaura with Goyo Maru and embarks the No. 2 Maizuru Special Naval Landing Force (2nd Maizuru SNLF) via Saipan then Truk arriving January 4, 1942.

On January 20, 1942 departs Truk for Operation R the invasion of Rabaul and Kavieng. On January 23, 1942 lands three companies of 2nd Maizuru SNLF at Kavieng and the next day transports three Daihatsu barges to Rabaul. On January 26, 1942 departs Rabaul and the next day to Kavieng then departs for Kure arriving February 8, 1942.

On February 18, 1942 departs Kure with a convoy including Shoka Maru, Chowa Maru and Akibasan Maru for Truk that arrives a week later. On March 21, 1942 departs for Rabaul with the same convoy arriving five days later. Afterwards, returns to Truk. On April 22, 1942 assigned to R District Command, Transport Force.

On April 28, 1942 departs Truk for Operation MO the invasion of Tulagi with Okinoshima (flagship of Rear Admiral Shima) and minelayer Koei Maru escorted by destroyers Kikuzuki and Yuzuki, subchasers Toshi Maru No. 3 and Tama Maru No. 8, special duty minesweepers WA-1 and WA-2, Hagoromo Maru, Noshiro Maru No. 2 and Tama Maru.

On May 3, 1942 the invasion force enters Tulagi Harbor and Azumasan Maru successfully unloads and anchors northeast of Tulagi. On May 4, 1942 at 8:15am, attacked by U.S. Navy carrier planes from USS Yorktown CV-5 and sustains some damage. Afterwards, departs for Rabaul and the damage is repaired.


On July 30, 1942 arrives Yokosuka and undergoes maintenance and repairs. On September 5, 1942 arrives Maizuru and loads equipment and is attached to the Combined Fleet. Two days later, embarks the No. 4 Maizuru Special Naval Landing Force (No. 4 Maizuru SNLF) and departs arriving Yokosuka two days later and transfers the troops and cargo to Light Cruisers Oi and Kitakami. On September 16, 1942 departs Yokosuka bound for Rabaul.

On October 10, 1942 at Rabaul attached to the Combined Fleet to transport the 17th Army under the command of Lt. General Hyakutake Harukichi as part of a high speed convoy (first assault convoy) transporting roughly 4,500 soldiers, artillery, engineers, tanks plus cargo via Shortland Harbor to reinforce Guadalcanal.

On October 12, 1942 departs Rabaul transporting the Imperial Japanese Army (IJA) soldiers and cargo as part of a high speed convoy "Tokyo Express" with Sado Maru, Azumasan Maru, Kyusyu Maru, Nankai Maru, Sakito Maru and Sasako Maru, escorted by destroyers Akizuki, Yudachi, Harusame, Samidare, Murasame Shigure, Shiratsuyu and Ariake that proceed southeast to Shortland Harbor. At 2:00pm roughly 100 miles off Shortland spotted by U.S. aircraft and attacked by 30 planes without damage. At 3:30pm again targeted by U.S. aircraft without damage. On October 13, 1942 departs Shortland Harbor and overnight proceeds southeast down "The Slot" to Guadalcanal.

Sinking History
On October 14, 1942 around midnight the transports arrive off Tassafaronga Point on Guadalcanal. Azumasan Maru begins unloading near Bunani Point. At 6:00am six F4F Wildcats strafe the transports with one shot down and other damaged. At 10:30am U.S. aircraft from Henderson Field attack the transports including SBD Dauntless dive bombers, Airacobras and eight F4F Wildcats and a PBY Catalina. Sasako Maru was hit by a bomb that started a fire and deliberately run aground but is a total loss. At 11:50 B-17 Flying Fotresses bomb the transports and hit Azumasan Maru causing fires and is run aground. Around 1:30pm, U.S. aircraft again strike and Kyushu Maru was hit by a bomb and set on fire and is deliberately run aground.

On October 15, 1942 Azumasan Maru was abandoned and continues to burn and remains afloat and is subjected to more air raids by U.S. planes including B-17 Flying Fortresses. On October 16, 1942 still burning and again bombed. Overnight, the damaged ship slips off the reef and sank into deep water off Ruaniu. Officially removed from the Navy list on February 1, 1943.

During the 1970s, the shipwreck was found by SCUBA divers upright and intact in excellent condition with the bow at a depth of 130' / 40m and the bridge at a depth of 205' / 62m. Locally known as "Deep Ruinin Wreck". The bow gun is encrusted with soft coral and large fish are often found around the shipwreck.

Sometimes incorrectly referred to as "Asumasan Maru" [sic Azumasan Maru].
Combined Fleet - IJN AZUMASAN MARU:  Tabular Record of Movement
Naval History and Heritage Command (NHHC) Japanese Naval and Merchant Shipping Losses During World War II by All Causes page 34
"Date: October 15, 1942 / Azumasan Maru / Passenger-Cargo / 7,623 Tons / 9-25S, 159-55E / Sunk by Army Aircraft, Navy Carrier- Based Aircraft, Navy Land- Based Aircraft, Marine Land- Based Aircraft"

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Last Updated
October 19, 2021


130' bow
205' bridge

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