The Oshima was a steel-hulled, three-masted gunboat constructed at a shipyard in Kobe. Her design was based on a modified French template, with contributions from the distinguished French naval architect Louis-Emile Bertin, one of several foreign advisors who helped modernize Japan's navy during the Meiji era. What set the Oshima apart from her contemporaries was her propulsion: a vertical triple-expansion reciprocating steam engine with two boilers driving two screws, giving her a speed of 13 knots. She was the first ship built entirely in Japan to carry this type of engine, marking a milestone in the country's industrial development. Named after the island of Oshima off Shizuoka prefecture, the gunboat was modest in size but represented Japan's growing ability to design and build modern warships domestically rather than purchasing them from European yards.

The Oshima saw her first combat during the First Sino-Japanese War of 1894-1895, when she was fitted with additional armament: three 120mm guns and three 47mm Hotchkiss guns supplementing her original battery. Assigned to the IJN 2nd Fleet in a reserve capacity, she patrolled the waters between Korea, Dairen, and Weihaiwei -- the same strategic triangle that defined Japan's naval operations throughout the conflict. On 21 March 1898, she was redesignated as a second-class gunboat, a bureaucratic acknowledgment of her aging capabilities as newer and more powerful vessels entered service. When the Russo-Japanese War erupted in 1904, the Oshima was called back to active duty to assist in the Siege of Port Arthur, joining the massive naval operation that sought to neutralize Russia's Pacific Fleet.

The waters around Port Arthur in 1904 were among the most dangerous in the world -- not only because of Russian mines and shore batteries but because of the dense fogs that frequently blanketed Liaotung Bay. On 18 May 1904, the Oshima was operating off Port Arthur when heavy fog closed in. Visibility dropped to almost nothing. In the confusion, the gunboat collided with another Japanese vessel. The damage was fatal. The Oshima sank in the early hours of 19 May, settling into the seafloor of the bay at a position now recorded in naval charts. She was struck from the navy list on 15 June 1905. The Oshima was one of several Japanese ships lost during the Port Arthur campaign to causes other than direct enemy action -- collisions, mines, and the relentless attrition of operating warships in hostile waters for months on end. Her loss underscored a truth of naval warfare that the age's dramatic battles sometimes obscured: the sea itself was always the most dangerous adversary.