Japanese submarine Yu 4

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 4 was a unit of the Yu 1 subclass.^[1]

The Hitachi Kasado Works (Hitachi Kasado Seisakujo) at Kudamatsu, Japan, constructed Yu 4.^[1][2] Records of the details of the construction of Yu 4 have not been discovered, but the earlier Yu I-type submarines were laid down and launched during the latter half of 1943 and entered service at the end of 1943 or early in 1944.^[2][3]

Yu 4 spent her operational career in Japanese home waters.^[4] Surviving records of the activities of Imperial Japanese Army submarines are fragmentary,^[3][5] and no records have been discovered describing her specific activities in support of any particular operation.^[2][4]

World War II ended with the cessation of hostilities on 15 August 1945.Yu 4 surrendered to the Allies later in August 1945.^[2] She subsequently either was scuttled or scrapped.^[4]

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