SS Fuso Maru was a Japanese ocean liner that was torpedoed by the United States Navy submarine USS Steelhead (SS-280) in the South China Sea 280 nautical miles (520 km) northwest of Cape Mayraira, Luzon, the Philippines, at (18°51′N 122°55′E / 18.850°N 122.917°E / 18.850; 122.917), while she was travelling in Convoy MI-11 from Moji, Japan, to Miri, Borneo.

She was renamed Fuso Maru when she was bought by the Japanese company Osaka Shosen K. K. - OSK Line on 24 December 1923.

She was most likely disarmed because of the international prohibition against hospital ships carrying armament, and she was painted white with a green horizontal strip and red crosses on her sides and funnel.

[citation needed] Shortly after sunrise on 15 April 1943, Allied aircraft attacked Fuso Maru three times near the Shortland Islands near (03°33′S 152°20′E / 3.550°S 152.333°E / -3.550; 152.333).

[citation needed] Fuso Maru returned to service as a troopship later in 1943 and was repainted overall grey and again armed with antiaircraft guns.

The convoy was attacked in the South China Sea 280 nautical miles (520 km) northwest of Cape Mayraira, Luzon, while it was proceeding from Moji, Japan to Miri, Borneo,[1] by a United States Navy submarine wolfpack patrolling the Luzon Strait under the command of Captain (later Rear Admiral) Lewis S. Parks.

Aboard Fuso Maru, 40 men were assigned to duty as lookouts, including Imperial Japanese Army artillerymen and infantrymen.

At 4:55 AM, one lookout spotted a torpedo approaching the ship and her captain ordered her rudder turned hard to port, but it was too late.

Fuso Maru bucked and trembled from the explosion and the blast blew upwards, destroying several lifeboats that were on deck.

The ground vehicles carried as deck cargo broke loose and fell onto men swimming in the water.

Seventy men of the 2nd Company, Sixth Aviation Signal Regiment, 12 other passengers, and 22 crew members also perished, bringing the death toll to 1,384 people.