Hōkoku-Maru class Auxiliary Cruiser, Aikoku Maru (1943)

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Hōkoku-Maru class Auxiliary Cruiser, Aikoku Maru


Aikoku Maru was laid down at the Mitsui Tamano shipyards in Okayama Prefecture on December 29, 1938. The ship’s design was developed as a cargo-passenger liner for the Osaka Shosen Lines transport company, which provided regular services to South America. The ship was tentatively named Kyoto. The liner boasted very luxurious cabins. Much of the ship’s construction benefited from government subsidies introduced in 1936 to encourage the construction of large, high-speed transport ships and tankers that could be quickly converted for military use. The ship was launched on April 25, 1940, and at the same time received the name Aikoku Maru.

Despite the rich decoration of the liner’s cabins, the military nevertheless said that there was a need to continue to use the ship as a transport for troops. Also during construction, opportunities were provided for launching aircraft and placing artillery installations.

Modernization and refurbishment


Immediately upon completion on August 31, 1941, the Aikoku Maru was officially requisitioned by the Imperial Navy. By September 5, the ship was refitted and armed for use as a raider. Four 152 mm guns, two QF 12-pounder 76 mm guns, two 13.2 mm Type 93 machine guns, and two four-tube 533 mm torpedo tubes were installed. In addition, on October 15, 1941, the installation of one 1100 mm and one 900 mm searchlight and boom for lifting the Kawanishi E7K aircraft was completed.

Service history


On October 15, 1941, the 24th Raider Squadron (CruDiv 24) was created, consisting of Aikoku Maru, Hōkoku Maru, and Kiyosumi Maru. In late November, the Aikoku Maru and sistership Hōkoku Maru were sent on duty at Jaluit Atoll in the Marshall Islands, in preparation for the upcoming military action against the United States.

On December 13, 1941, the Aikoku Maru and Hōkoku Maru sank the American merchant ship SS-Vincent, which was en route from Australia to Panama with a cargo of rice. All nine officers and 27 crew survived and were picked up by the Hōkoku Maru.

In December, a reconnaissance seaplane from the Aikoku Maru spotted the American cargo ship SS-Malama heading towards Manila. The plane did not return to the raider, and despite a lengthy search operation by two Japanese ships and a second Kawanishi E7K, no traces of the plane could be found. On January 2, 1942, a second seaplane spotted the SS Malama south of Cook Island, and after shelling the transport, the ship was forced to stop. The crew abandoned Malama, after which the ship was sunk. Apart from the missing pilot of the first plane, there were no casualties on either side, and the campaign was completed on January 20.

In February, after visiting Oita, where 76 prisoners of war were taken, the CruDiv24 unit returned to Hashira Island.

On February 14, 1942, at the naval base in Kure, the Aikoku Maru replaced the outdated four 152 mm guns with eight 140 mm naval guns. The seaplanes were replaced with Nakajima A6M2-N. In addition to re-equipment, re-equipment was carried out to allow the carriage of torpedoes in the holds, with the aim of serving as a submarine tender. In this role, Aikoku Maru and Hōkoku Maru were dispatched with the 6th Fleet on 10 March to support submarine operations off the east coast of Africa and Mozambique.

On April 16, 1942, Aikoku Maru sailed from Hashira with the cruiser IJN Katori via Singapore and Penang to conduct exercises in the Indian Ocean, as well as to provide support for submarine divisions SubRon 8, SubDiv 1 in the western Indian Ocean. Along the way, Aikoku Maru refueles several submarines.

On April 30, 1942, the raider Aikoku Maru arrived in Penang and left port with Hōkoku Maru on May 5, 1942.

At the end of March, the two raiders returned to Kure, where CruDiv 24 was officially disbanded and, from early April, the ships were transferred to SubRon8, operating from a base on Penang Island to support submarine operations in the western Indian Ocean.

On May 9, 1942, the Aikoku Maru captured the Dutch tanker Genota 480 miles off Diego Suarez, Madagascar.

On June 5, a raider sank the British freighter Elysia, which was carrying Allied troops.

On June 17, 1942, the raider met with the SubRon 8 submarine division.

On July 12, Aikoku Maru, near Ceylon, captured the New Zealand-registered cargo ship Hauraki. The Japanese prize team headed to Japan on the captured ship, but the New Zealand crew managed to damage the engine and some equipment along the way.

On August 10, 1942, Aikoku Maru arrived at Seletar, a naval base in Singapore. There, two Aichi E13A aircraft, 70 torpedoes, and two twin 25 mm Type 96 anti-aircraft guns were loaded on board. The raider continued to serve in Penang until the end of August under the command of Commander Tamotsu Oishi.

In September 1942, Aikoku Maru was assigned to the 8th Fleet and was given the task of transferring the 38th Infantry Division to Rabaul in order to strengthen the force group on the island of Guadalcanal, Solomon Islands. Following the completion of this mission on October 10, Aikoku Maru returned to duty in the Indian Ocean with Hōkoku Maru.

Battle of the Cocos Islands


On November 11, two Japanese raiders attacked the Dutch tanker Ondina, which was escorted by the minesweeper HMIS Bengal southwest of the Cocos Islands. Hōkoku Maru was closer and attacked first, but a shot from Ondina damaged the starboard torpedo tube, causing the torpedoes to detonate. The resulting fire quickly got out of control, and as a result of a series of explosions in the stern, the ship quickly sank. Aikoku Maru did not pursue HMIS Bengal, but set course to intercept Ondina, which attempted to break away. The raider’s guns hit the tanker 6 times, and two fired torpedoes made holes in the tanker. After which the raider went to provide assistance to the survivors of the Hōkoku Maru, then returned to Penang, and from there to Singapore and Rabaul.


“Ondina” and “Bengal” are engaged in battle with Japanese auxiliary cruisers. Painting by artist Fred Bloom, 2010.

On 16 December 1942, Aikoku Maru was reassigned to the 8th Fleet, primarily as a troop transport to support the operation in New Guinea. While unloading supplies at Madang on December 18, the raider was attacked by an air raid by American bombers, but US aircraft failed to damage the ship. On December 29, 1942, Aikoku Maru returned to Kure.

British ships - tanker and corvette

On January 5, 1943, as part of “Operation C” (strengthening the force grouping in New Guinea), the 209th Flying Battalion, the 14th Air Repair Base and others were embarked at Aikoku Maru, for a total of 691 people, plus 34 vehicles embarked at Busan in Korea, after which the raider arrived on January 14 in Rabaul.

On January 24, 1943, Aikoku Maru arrived at Qingdao and from there proceeded to Cebu and Palau, where troops and cargo were loaded to provide reinforcements at Wewak, New Guinea on February 23. The cruiser returned to Kure on April 5.


Corvette Fremantle (J246), the same type as the Bengal. State Library of Victoria

On 10 July 1943, in a convoy operation with the carrier IJN Un’yō, Aikoku Maru was attacked by the American submarine USS Halibut (SS-232) 170 nm north of Truk, which fired six torpedoes. One torpedo hit the raider, causing minor damage. On the way back, on July 15, the cruiser was again attacked by the USS Tinosa (SS-283), whose four torpedoes missed. On September 2, 1943, Aikoku Maru returned to Kure.

On October 6, 1943, Aikoku Maru returned to the Tamano shipyard for repairs and refitting, as well as the installation of armament, which included two 152 mm guns and four Type 96 single-barrel mounts. Armament installation and repair work were completed on December 31, 1943.


Explosion on the auxiliary cruiser Aikoku Maru


On January 21, 1944, the raider Aikoku Maru hosted 629 men of the 66th Naval Unit, with ammunition, supplies and construction materials. 300 kilometers northwest of the Truk Islands, the convoy was attacked by the American submarine USS Trigger (SS-237), which managed to sink the minelayer Nasami and the transport Yasukuni Maru. Aikoku Maru was undamaged and reached the Truk Islands by 1 February. After this, the raider made an unsuccessful trip to Brown Island and on February 16 returned to the Truk Islands, where most of the ships had already been evacuated due to the threat of a US attack. The Aikoku Maru began loading ammunition, preparing for evacuation to Rabaul, and deploying troops of the 1st Airborne Brigade. However, the evacuation could not be completed. On February 17, 1944, American troops launched an attack on the Truk Islands, which became known as Operation Hailstone.

At 0815, Aikoku Maru was attacked by Avenger bombers from the aircraft carriers USS Essex and USS Intrepid. At the same time, a TBM Avenger TBM-1C (tail number BN 25270) from the USS Intrepid, piloted by Lt. James Bridges, approached the ship over the water. While the Avenger was approaching the raider to attack, the bow of the ship was hit by two bombs dropped from aircraft of the aircraft carrier USS Essex. These bombs caused the detonation of ammunition in the holds of the bow. Some sources mentioned that Lieutenant Bridges’ plane probably fired a torpedo and tried to go up, but as a result of explosions on the ship, the torpedo bomber was severely damaged. Also, there are versions that the plane was probably damaged by anti-aircraft fire and crashed into the bridge, causing the detonation of ammunition in the hold. Whatever happened, it is known that Lt. Bridges’ TBM Avenger TBM-1C did not return to the aircraft carrier. As a result of the detonation of ammunition in the hold, the bow of the ship was torn off. The Aikoku Maru sank within two minutes, killing most of the 945 crew and stationed soldiers. Also, as a result of the explosion, the attacking American TBM Avenger aircraft of Lieutenant Bridges was also lost.

The auxiliary cruiser Aikoku Maru was removed from the navy list on March 30, 1944.

Today, the Aikoku Maru sinking site is a popular diving area in the waters of Truk Lagoon, at a depth of approximately 64 meters. Often in photographs of divers, you can see fragments of an anti-aircraft gun on the top of the deckhouse, scattered dishes and kitchen utensils in the galley of a sunken ship. The Aikoku Maru was first discovered by the famous French explorer Jacques-Yves Cousteau in 1969, but the ship was not identified until later. In July 1980, a Japanese team recovered the remains of approximately 400 bodies killed in the attack and erected a memorial plaque on the deck. But the remains of hundreds more sailors and soldiers remain at the site of the sinking.




“Aikoku-maru” in late camouflage. Ships of the Imperial Japanese Navy (Ships of the World, 1995, №500)

140-mm Hokoku-maru guns. The Maru Special No.53 Japanese support vessels.

The battle of the corvette “Bengal” with the Japanese auxiliary cruiser “Aikoku-maru”. Imperial War Museum

“Aikoku-maru” in late camouflage. Ships of the Imperial Japanese Navy

Aikoku Maru Memorial Sign


  • Gross-Tonnage: 10,439 t
  • Length overall: 160.8 m
  • Length between perpendicular: 152.25 m
  • Width: 20.20 m
  • Depth: 12.40 m
  • Draft: 8.8 m
  • Engine: 2 Diesel
  • Propeller: 2 shaft
  • Max Power: 19,427 BHP
  • Max speed: 21.148 kt


  • 8x1 - 140 mm 3rd Year Type Naval Guns
  • 4x2 - 25 mm Type 96 twin AA machine guns
  • 2x2 - 533 mm 6th Year Type twin torpedo tubes
  • 2 - Type 0 Recon Seaplane (Aichi E13A “Jake”)



What an interesting ship! A substantial main armament but weak AA weaponry. +1

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