Wreck of HIJMS Ōi (大井)

 crash site, shipwreck

Laid down at the Kawasaki Kobe Shipbuilding Yard in November 1919 as the fourth member of the Kuma Class of Light Cruisers, HIJMS Ōi commissioned into Imperial Japanese Navy Service in October 1921. Selected in 1928 to serve as the training ship IJN Naval Academy, Ōi provided over a decade of service training scores of Japanese sailors before changing naval doctrine and the advancing age of the Light Cruiser brought her into the Maizuru Naval Shipyard for a major overhaul in the advance of the coming war with the United States.

Converted from a traditional gun Cruiser to a "Torpedo Cruiser" layout, Ōi saw the majority of her topside weaponry removed in favor of an impressive battery of ten sets of Type 92 Model 3 quadruple torpedo tubes which enabled the ship to launch a devastating salvo of up to twenty "Long Lance" torpedoes from each side of the ship. Envisioned as the platform for devastating nighttime torpedo attacks on American naval formations, Ōi put to sea in September 1941 and joined Cruiser Division 9, IJN First Fleet for battle tactics training. Opening the Second World War by escorting the Battleships of the Combined Fleet as they provided backup for the Carrier Force attacking Pearl Harbor, the Ōi remained in home waters as the Japanese Navy systematically swept Allied Naval Forces from the Pacific and Indian Oceans, securing the "Greater East Asia Co-Prosperity Sphere" but also leaving ships like Ōi without an enemy to attack. Found to be essentially surplus in her Torpedo Cruiser layout, Ōi returned to the shipyard following the Battle of Midway and was extensively converted to serve as a Fast Transport.

Returning to frontline duty in October 1942, Ōi's once formidable torpedo battery was largely replaced by launching rails for landing craft and crew berthing areas for embarked passengers, modifications which would guarantee the ship extensive use across Japan's new Empire. Operating with the IJN Southwest Area Fleet through July 1943, Ōi ferried troops and supplies across the Bismarck, Solomon and Marshall Islands, as well as along the New Guinea coast as Japanese ground forces began fighting Allied forces in more and more areas. Reassigned to Singapore as part of Cruiser Division 16, Ōi and her crew carried out regular troop transport runs between Singapore and Penang to the Andaman Islands and Nicobar Islands through January 1944, after which she operated in primarily on the Java Sea shuttling Japanese forces to and from various defensive positions.

Following the Allied Invasion of Biak in May 1944, Ōi and her crew called at Surabaya and remained stationed there for over a month as guardships until early July 1944, when orders were received for the Cruiser and her sistership to make for Manila. Departing Javan waters on the 6th and arriving safely at Manila ten days later, Ōi loaded troops and supplies before departing Manila for Singapore under escort by the Destroyer HIJMS Shikinami at 1500hrs on July 18th. Steaming into heavy weather on the night of the 18th, both ships were approximately 570 miles South of Hong Kong when they were spotted by lookouts aboard the patrolling American Submarine USS Flasher (SS-249) at 1047hrs the following morning.

Not aware of the enemy Submarines' presence, crew aboard Ōi were likely unaware they were in any danger as they steamed through the heavy seas until their ship was struck in the Stern by two torpedoes at 1111hrs. Though one of the shots was a dud and failed to detonate on impact with her hull, the second torpedo fired by Flasher struck Ōi at a glancing angle at her rear engine room, opening up a large hole in her hull and flooding the entire compartment. Going dead in the water and settling by the Stern, Ōi's crew raced to effect damage control measures on their ship as it was lashed by the foul weather, however after several hours the Ōi was clearly losing her battle to stay afloat as progressive flooding claimed several large areas of her hull, likely aided by her numerous reconstructions reducing her watertight integrity.

Shortly after 1500hrs on July 18th the order was passed to abandon ship. After HIJMS Shikinami removed all her surviving crew and withdrew from the area, HIJMS Ōi rolled onto her Port side and sank Stern-first at this location on July 19th, 1944. 153 members of her crew were lost in her sinking.

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