The Rio De Janeiro Maru was laid down during May 1929 at the Nagasaki yard of Mitsubishi Shipbuilding, ordered by the Osaka Shosen Kaisha (OSK) Line as a passenger-cargo liner. It was launched during November 1929 and completed in May 1930. Her maiden voyage commenced on June 1st 1930 from Kobe to South America. The ship could carry approximately 1,140 passengers with cargo space available in five holds.

A sister ship to the Rio de Janeiro Maru was the Buenos Aires Maru which was commissioned during October 1929.

In April 1934 the ship ran aground in the Mississippi River estuary.

A round the world service commenced during January 1937 commencing at Kobe, then calling in at Yokkaichi, Yokohama, Kobe (2nd), Hong Kong, Singapore, Colombo, Durban, Cape Town, Rio de Janeiro, Santos, Montevideo, Buenos Aires and returning via Santos, Rio De Janeiro, Belem, Cristobal, Balboa, Los Angeles, Yokohama and Kobe.

The onset of World War Two saw the Rio De Janeiro Maru requisitioned by the Imperial Japanese Navy during October 1940. The ship was sent to Kure Navy Yard for conversion to an auxiliary transport, this included the addition of 25mm anti-aircraft guns, the conversion was completed by the end of November 1940. After four months in this role the ship visited Harima's shipyard for conversion to an auxiliary submarine depot ship. The conversion included improved goods storage, a medical facility and motor launch loading equipment. The armament was considerably beefed up - four 5.9 inch guns and range finder were added. This was completed early in May 1941.

Late in November 1941 the ship headed out of Sasebo for Palau with other members of the fleet. The day after the attack on Pearl Harbour the ship is part of the fleet involved in the support of the invasion of Malaya, initially docking at Camranh Bay. After a month here the ship sailed to Singora, Malaysia to unload personnel and equipment. From here it was on to Kota Bharu, Brunei and back to Sasebo by early April.

On May 14th 1942 the Rio De Janeiro Maru sailed from Sasebo for the Dutch East Indies. Whilst in the Balbac Strait on the night of May 29th 1942 the ship is hit by a torpedo believed to be from the USS Swordfish (SS-193), putting a large hole in hold No.1. Action by some members of the crew is successful in sealing the leak. The repair ships Asahi Maru & Yamabiko Maru take the ship in tow to Singapore. Repairs are made in the former King George V Graving Dock, once completed the ship sailed to Sasebo at the very beginning of July. During the third week of July the ship sails from Sasebo, on the night of July 27th east of Camranh the ship is hit by a torpedo from the USS Spearfish (SS-190). Though damaged the Rio De Janeiro Maru is able to reach Hong Kong for repairs. By the beginning of August the ship has reached Camranh Bay.

During the first half of 1943 the ship was operating out of Surabaya, Java as a tender in the Southwest Area Fleet, visiting Kokas, Ambon, Balikpapan and Sorong. The trip to Ambong included the transport of Allied prisoners of war. Further destinations were Tarakan, Davao and Manila, arriving here in the middle of September. Whilst here the ship was demilitarized and became a civilian transport based at Sasebo. The latter half of 1943 saw the Rio De Janeiro Maru visiting Balikpapan, Makassar, Batavia, Surabaya, Singapore, Cap St Jacques, Takao, Sasebo, Kure & Osaka. The trip to Batavia involved the movement of 200 prisoners of war.

After arrival at Osaka the ship is transferred to the Aioi shipyard for modifications. The work is completed by the middle of January 1944 when the ship departed for Miike, followed by a trip to Kure for the loading of ammunition destined for the light cruiser Agano at Truk. At Yokosuka further supplies of armaments, food and mail are loaded before leaving on February 3rd 1944 for Truk, arriving there eight days later.

Six days after arrival at Truk the American forces launch operation Hailstone with the intent to eliminate the use of Truk as a Japanese navy base. The action is successful - sinking thirty one transports, ten naval vessels and destroying or damaging 300 aircraft. The Rio De Janeiro Maru is an early casualty, whilst at anchor east of Uman Island, the ship is hit by 1,000lb bombs in one of the first attacks on February 17th. The ship came to rest on her starboard side at depth of 115 feet and is removed from the Navy List on March 31st 1944.

The ship came to rest on her starboard side relatively intact although whilst on the surface fires had burned until she sank. The sea bottom here is about 130 feet, with parts of the ship rising up to with forty feet of the surface. The increasing popularity of wreck diving, coupled to the large number of wrecks here and the location of Truk itself have led to the accurate reporting of the ship's location, its condition and contents. This is the fourth largest wreck at the Truk Lagoon, located about 500 yards from shore on the east side of Uman Island. .

Well reported are the two deck guns (with fifteen foot barrels), the two bronze propellors, the degaussing wires around the hull, the presence of the still visible ship's name on the hull. The No.1 hold contains artillery shells and debris, the No.2 hold has large guns with winches and cargo equipment nearby. The other holds contain coal, guns, beer bottles, oil drums and living quarters. China and other pottery can still be found in the galley and some of the portholes in the bridge area still contain glass.

At some point in recent times the port side bow was apparently used as a mooring point for diving vessels, this has led to damage which has resulted in the collapse of the bow structure.

A publicity view of the Rio De Janeiro Maru

Builder: Mitsubishi Shipbuilding, Nagasaki
Launched: 1929
Length: 450 feet
Beam: 62 feet
Draught 39 feet
Weight: displacement 9,627 tons
Deadweight: 12,000 tons
Engines: Two Mitsubishi Sulzer 6ST68 diesel engines, each producing 6,000hp at 120 rpm
Auxiliary engines: Three 4 cycle engines totalling 1,000hp at 250rpm
Screws: Two
Service Speed: 17.6 knots
Passengers: 60 first, 1,076 third

Page added July 23rd 2009

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