In the final two years of World War II, the Imperial Japanese Army constructed transport submarines — officially the Type 3 submergence transport vehicle and known to the Japanese Army as the Maru Yu — with which to supply its isolated island garrisons in the Pacific Ocean. Only submarines of the Yu I type were completed and saw service. The Yu I type was produced in four subclasses, each produced by a different manufacturer and differing primarily in the design of their conning towers and details of their gun armament. None carried torpedoes or had torpedo tubes. Yu 1 was both the first Maru Yu submarine constructed and the lead unit of the Yu 1 subclass.[1]
Yu 1 was laid down on 23 June 1943 by the Hitachi Kasado Works (Hitachi Kasado Seisakujo) at Kudamatsu, Japan.[1] She was launched on either 16[2] [3] or 29[1] October 1943 (according to different sources) and delivered to the Imperial Japanese Army sometime between 22 and 31 December 1943.[1]
Yu 1 initially remained in Japanese home waters while the Japanese Army constructed additional submarines of her class and established a training program for their crews.[4] In May 1944, the Army created its first submarine combat unit (jissen butai), the Manila Underwater Transport Detachment (Manira Sensuiyuso Hakentai), consisting of Yu 1, her sister ships and, and a mother ship.[4] The detachment got underway from Japan on either 28[4] or 30[2] May 1944 (according to different sources) bound for Manila on Luzon in the Philippines.[2] [4] The vessels had a difficult voyage which included a number of mechanical breakdowns, but finally arrived at Manila on 18 July 1944.[4] After their arrival, the three submarines underwent repairs and thorough overhauls.[4]
On 20 October 1944, United States Army forces landed on Leyte, beginning both the Battle of Leyte and the broader Philippines campaign of 1944–1945.[4] In November 1944, all three submarines got underway on their first supply run to Leyte.[4] Yu 2 never arrived,[4] but Yu 1 and Yu 3 reached Ormoc on Leyte's west coast on 27 November 1944 and discharged a combined 600 bags of white rice, 50 boxes of field rations, and 300 boxes of radio batteries.[4]
In December 1944, Yu 1 and Yu 3 were sent to San Fernando on the northwest coast of Luzon.[4] On 2 January 1945, U.S. aircraft surprised Yu 1 on the surface and sank her in Lingayen Gulf just off Port Poro on Luzon's coast.[2] [4]