Sanyo Maru was built by Mitsubishi shipbuilding at
Nagasaki as a merchant ship for the Osaka Shosen K. K. Line. Laid down December 26, 1929. Launched July 11, 1930. Completed on October 15, 1930.
On November 7, 1930 departed for her maiden voage from Kobe to New York. During 1931 she made another voyage to New York. During 1932 she voyaged to Savannah and New York. From 1933 until 1939 operated between Kobe and New York.
On August 6, 1941 requisitioned by the Imperial Japanese Navy (IJN) at Sasebo. The vessel was converted to begins conversion to a 8 seaplane carrier/tender, with two 150-mm/45 cal single-mount guns, two Type 93 13mm machine guns and a catapult are installed. The conversion is completed on August 15, 1941, and redesignated as a seaplane tender carrying six F1M2 Pete and two E13A Jake and two E8N2 Dave. Aircraft tail codes were "ZIII-xx". During September 1941 steamed to Camranh Bay, then returned to Sasebo.
On December 4, 1941 joins Operation E, the invasion of Malaya, departs Samah, Hainan Island with the Kamikawa Maru and Operation M Philippine invasion force.
On December 8, 1941 operates off Singora (Songkhla) and on December 14, 1941 departs for Camranh Bay and while underway torpedoed by USS Seawolf (SS-197) and hit by a dud Mark-14 steam torpedo that caused only slight damage.
Afterwards, she remains on station and continues air operations. On December 16, 1941 arrives at
Takao then departs the next day to support the Japanese landings at Lingayen Gulf on Luzon.
On December 21, 1941 departs Aparri bound for Vigan to begin air operations. The tender SANUKI MARU arrives later that day. A floatplane base is established in the Vigan area. Sixteen floatplanes arrive that day: six F1Ms and one E13A from the SANYO MARU, six F1Ms from the SANUKI MARU and three E7Ks from the light cruisers NAKA and NATORI.
29 December 1941:
Departs Vigan for Jolo, Philippines.
31 December 1941:
Arrives at Jolo.
7 January 1942: The Invasion of Dutch Borneo:
The 21st Air Flotilla’s tenders SANYO and SANUKI MARUs provide air cover for Rear Admiral (later Vice Admiral) Hirose Sueto's (former CO of AOBA) Tarakan Occupation Force that departs Davao that day.
The Tarakan invasion convoy carrying MajGen Sakaguchi Shizuo’s 56th Mixed Infantry Group (Sakaguchi Brigade) and the Kure No. 2 SNLF includes Army transports TSURUGA, LIVERPOOL, HAVANA, KURETAKE, NICHIAI, HITERU, TEIRYU, HANKOW and EHIME MARUs, Navy transports KUNIKAWA, KANO, KAGU, KOKUYO and RAKUTO MARUs.
The convoy’s escort is provided by Rear Admiral (later Vice Admiral) Nishimura Shoji’s DesRon 4’s light cruiser NAKA with DesDiv 2’s HARUSAME, SAMIDARE, YUDACHI and MURUSAME, DesDiv 9’s ASAGUMO and MINEGUMO, NATSUGUMO and DesDiv 24’s UMIKAZE, Kawakaze, YAMAKAZE and the SUZUKAZE.
Rear-Admiral Hirose’s No. 2 Base Force includes patrol boats P-36, P-37 and P-38, Minesweeper Division 11’s W-13, W-14, W-15, W-16, 30th Minesweeper Division’s W-17, W-18 and Subchaser Div 31’s Ch 10, Ch-11 and Ch-12 and other auxiliary ships.
8 January 1942:
The SANYO MARU, patrol boats P37 and P38 rendezvous with units of the No. 2 Base Force (Central Force) and proceed to Tarakan, Borneo.
10 January 1942:
NE Dutch Borneo. The SANYO MARU covers the Tarakan Occupation Force scheduled to land troops the next day. Two of her F1M2 ‘Pete’ scouts strafe a surfaced submarine. Later, they attack a Glenn Martin B-10 of 1-VIG-I they misidentify as a “Blenheim, one of three they see taking off from Samarinda. The bomber crash-lands on Tarakan's airfield.
11 January 1942:
Rear Admiral Hirose's Occupation Force invades Tarakan.
Afterwards, Sanyo Maru joins the Japanese
convoy bound for Balikpapan.
On January 23, 1942 in the afternoon Allied aircraft attack the convoy including U. S. Army Air Force (USAAF) B-17 Flying Fortresses and Dutch B-10s escorted by twenty Brewster Buffaloes from 2-VLG-V and 3-VLG-V. During the attack, Sanyo Maru was damaged but proceeds with the force.
On January 24, 1942 Sanyo Maru seaplanes provide air cover for the Japanese force that lands southeast of Balikpapan. On January 25, 1942 departs
northward and three days later arrives Davao.
On January 30, 1942 departs Davao
via Subic Bay bound for Camranh Bay. On February 1, 1942 the 12th Seaplane Tender Division is disbanded and
Sanyo Maru was attacked directly to the Third Fleet. On February 8, 1942 arrives Camranh Bay.
On February 18, 1942
departs Camranh Bay to operate west of Anambus Island off Malaysa to provide air cover for Operation J the Japanese invasion of Java.
On March 1, 1942 Sanyo Maru arrives at
Eretan-wetan on the north coast of western Java. During the day, Royal Air Force (RAF) Hurricans from No. 605 Squadron strafe the Japanese forces landing and are intercepted by bi-planes from Sanyo Maru and claim one shot down but none are lost.
On March 10, 1942 Sanyo Maru was assigned to the
Second Southern Expeditionary Fleet at Surabaya, Java. That same day, her seaplane code is changed to P-?? (two digit aircraft code). Afterwards, supports Japanese operations in the Burma and Andaman Islands area. On April 1, 1942 departs to return to Java.
10 April 1942:
Takao, Formosa. The SANYO MARU is assigned to the 2nd Naval Base Force of the new Third Fleet’s CarDiv 12 with the seaplane tenders KAMIKAWA and SANUKI MARUs.
8-16 May 1942: Operation "S" – The Seizure of the Lesser Sunda's:
Departs Surabaya. Begins air support of a combined Army/Navy Operation to "sanitize" the local area that includes Lombok, Sumbawa, Flores and Bali Islands. No resistance by the Dutch is encountered.
24 May 1942:
Departs Surabaya for Sasebo.
3 June 1942:
Arrives at Sasebo.
26 June 1942:
Departs Sasebo for Surabaya.
5 July 1942:
Arrives at Surabaya. Prepares for the upcoming operations.
14 July 1942:
The SANYO MARU’s aircraft tail code is changed to “W-xx”.
24 July 1942: Operation "T" - The Banda Sea Operation:
In Vice Admiral Takahashi’s 2nd Southern Expeditionary Fleet, Southwest Area Fleet. The SANYO MARU departs Amboina and provides air cover for Rear Admiral (later Vice Admiral) Hatakeyama Kouichiro’s (former CO of KINUGASA) 24th Special Base Force’s landing operations on the Tanimbar Islands that are also supported by CruDiv 16’s light cruiser IZUSU and the fleet torpedo boat TOMORZURU.
27-30 July 1942: Operation “T” – The Seizure of the Tanimbar Islands.
Departs Surabaya. The SANYO MARU begins air support operations for the T Operation. While no resistance is encountered at Aru, Bakar or Tanimbar, the first landing at Kai Island is repulsed on the 28th. With additional reinforcements, including air support from the SANYO MARU, the island is overrun and occupied by the 29th of July. The SANYO MARU loses one F1M2 to ground fire.
2 August 1942:
Provides anti-submarine and anti-aircraft support in Ambon area.
After the American landings at Guadalcanal and Tulagi, Sanyo Maru arrives at Shortland on August 10, 1942. On the 28th, the "R" Area Air Force is created, with Sanyo Maru in the No. 2 Group, her E13A Jake perform long-range reconnaissance and anti-submarine missions, A6M2-Ns "Rufe" and F1M2 Pete for light bombing, convoy-escort duty. The R-Area Air Force is based in Shortland Harbor with Rekata Bay as a forward base.
14 September 1942:
Guadalcanal. During an attempt to retake Henderson Field, the R-Area Air Force provides air support. The tenders SANYO, KAMIKAWA and SANUKI MARUs and the CHITOSE launch 19 F1M2s, each armed with 60-kg bombs, escorted by two of the KAMIKAWA MARU's A6M2-Ns. At 1730, near Lunga Point, Guadalcanal, Gruman F4F-4 “Wildcats” intercept the Rufes and one is shot down. The other Rufe escapes and the pilot claims two F4Fs, although none are lost.
Between 1825 and 1830, more F1M2s drop bombs over Henderson Field, but only a few bombs hit the airstrip, causing small fires and destroying a Bell P-400 “Airacobra” that had already been consigned to the scrapyard.
As the Petes retire, a Marine F4F-4 Wildcat of fighter squadron VMF-224, engages one of SANYO MARU planes and shoots it down. Another Wildcat forces a F1M2 down five miles E of Savo Island.
On September 24, 1943 the Sanyo Maru arrives at Shortland.
9 October 1942:
SE of New Georgia. Eight F1M2 Petes from he ship are flying top cover at 14,000' over a convoy consisting of seaplane tender Nisshin and destroyer escorts. They are transporting a cargo of heavy weapons to Guadalcanal. Grumman F4F-4s of VF-5, escorting seven SBD “Dauntless” dive-bombers and four TBF “Avengers” against the convoy, encounter the eight F1M2s, but the floatplane pilots manage to evade. The Petes then join in protecting the Nisshin from the American bombers. The floatplanes claim seven SBDs shot down, but all the Americans return to Henderson Field.
On October 22 Sanyo Maru arrives at Yokosuka, and departs on the 29th.
On November 1, 1942 Sanyo Maru and Sanuki Maru are attached to the 4th Fleet as tenders for the 958th Kokutai. Aircraft tail code is changed to "P2-XX".
10 November 1942:
Vice Admiral (later Admiral) Kondo Nobutake's (former CO of KONGO) plans to land 14,500 men, heavy weapons and supplies of LtGen Sano Tadayoshi's 38th "Hiroshima" Infantry Division and the Sasebo No. 8 Special Naval Landing Force on Guadalcanal. Rear Admiral (later Vice Admiral) Tanaka Raizo's (former CO of KONGO) DesRon 2’s twelve destroyers will escort an 11-ship high-speed reinforcement convoy.
Three F1M2 Petes from the Sanyo Maru from Rekata Bay.
14 November 1942:
U.S. Navy and Marine aircraft attack Tanaka’s troop transports. They are opposed by Type 0 Mitsubishi A6M “Zekes”of the 204th Kokutai from Buin and by eight F1M2s from Rekata Bay. Two of the Petes are from the battleship HIEI, sunk the previous night in naval action. Three F1M2s are from SANYO MARU, two from KUNIKAWA MARU (including the flight leader) and one from SANUKI MARU.
An F4F-4 of VMF-112 attacks one of SANYO MARU's floatplanes, but the Pete pulls up sharply and knocks the wing off the Wildcat. The American pilot bails out 10 miles NW of the Russell Islands. He is later rescued by natives. The Americans claim two Zekes and six Petes shot down for the loss of one Wildcat. The 204th Kokutai loses two Zeros. Five of the R-Area Air Force's eight floatplanes, three of which are damaged, return to Rekata. One of the HIEI’s's F1M2s is lost. Sanyo Maru lost two planes, one in the mid-air collision, the other is forced to ditch.
On November 21, 1942, Sanyo Maru with the destroyer Amagiri departs Shortland for Rekata Bay. USS STINGRAY (SS-186) attacks the ships and fires four torpedoes at the Sanyo Maru and claims two hits but only causes minor damage but forced the vessel to return to Shortland.
On November 30, 1942 the same pair depart Shortland bound for Rekata Bay. On January 1, 1943 while at Rekata Bay, B-26 Marauders of the 69th Bombardment Squadron bomb from 7,000' and score a near miss.
On January 17, 1943 Sanyo Maru was towed to Truk and repaired, likely by Akashi.
On February 2, 1943 at Truk provisioned by Irako and again provisioned seven days later.
Afterwards, returns to Japan arriving at Kure on March 20, 1943 and departs on April 1, 1943. Reassigned to the Kure Base Unit and undergoes further repairs during July 1943 and n converted to a transport on October 1, 1943 at Hakodate.
On March 20, 1944 departs Tateyama as part of a reinforcement convoy via Truk, arrives at Saipan on April 2 and departs for Woleai on April 12. On the voyage, USS Harder (SS-257) is spotted by a Japanese aircraft and sinked escorting destroyer Ikazuchi, and Sanyo Maru continues unescorted. On April 13 arrives at Woleai and on the 14 Saipan, departing on the 22nd with destroyer Akikaze, and returning to Yokosuka on the 26th. The ship makes another trip to Saipan then departs on May 12 and arrives at Manila on May 21.
On May 24, 1944 departs Manila via Cebu carrying about 600 men of an anti-aircraft unit bound for Kao on Halmahera. On May 26, 1944 Sanyo Maru was north-northwest of Manado (Menado, Mendao) in the Celebes (Sulawesi) when hit by four torpedoes from a spread of five fired by the USS Cabrilla (SS-288). One torpedo hits the starboard No. 4 hold, another hit the No. 6 hold. The explosions killed thirty-five men of the anti-aircraft unit. At 5:32pm, she is abandoned. At 7:40pm, the ship sinks at approximately Lat 2° 46' N Long 124° 22' E. Officially removed from the Navy list on July 10, 1944.
Fates of the Crew
Captain Mori is among the survivors, but he is killed on July 8, 1944 and promoted Rear Admiral, posthumously.
Combined Fleet - Sanyo Maru Tabular Record of Movement
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March 31, 2021