From the wiki: “Yokosuka Naval Arsenal (Yokosuka kaigun kōshō) was one of four principal naval shipyards owned and operated by the Imperial Japanese Navy.
“In 1866, the Tokugawa shogunate government established the Yokosuka Seisakusho, a military arsenal and naval base, with the help of foreign engineers, including the French naval architect Léonce Verny. The new facility was intended to produce modern, western-style warships and equipment for the Tokugawa navy, and the construction of the arsenal was an important first step for the modernization of Japan’s industry.
“In 1865 the village of Yokosuka had comprised 1,263 inhabitants; by 1875, 3,673 villagers were mostly employed in the manufacture/fabrication of arsenal supplies … More formally the arsenal’s French-operated Ecole de Maistrance (School for Petty Officers) provided elementary and technical instruction in Japanese, the students being ‘chosen from amongst the workmen and foremen, who for the most part belong to the families of artisans … Some, however, were former samurai who sought service in the arsenal with the idea of bettering their condition after the official elimination of their class by the Meiji government.’
“… During the late 1870s, the reach of the arsenal extended firmly into the private domestic sector. The Home Department’s ironworks at Yokohama were placed under Yokosuka supervision, and provided materials to private manufacturers. Materials and bridges for the Shimbashi-Yokohama railway were also made at the arsenal, and later assembled, as were the iron rails of the Tokyo tramways.
“After the end of the Boshin War and the start of the Meiji Restoration, the new Meiji government took over control of the facility in 1871, renaming it the Yokosuka Zosenjo (Yokosuka Shipyards). The first dry dock was opened in 1871 (and is still in operation today), and Japan’s first domestically produced warship, Saiki, was completed the same year.
“The Yokosuka Naval District was established at Yokosuka, Kanagawa in 1884, as the first of the naval districts responsible for the defense of the Japanese home islands. The district was renamed the Yokosuka Naval Arsenal in 1903.
“Yokosuka became one of the main shipyards of the Imperial Japanese Navy in the 20th century, building numerous battleships such as Mutsu and Yamashiro, and aircraft carriers such as Hiryu and Shokaku. Naval aircraft were also designed at the nearby Yokosuka Naval Air Technical Arsenal.
“During the Pacific War, the Yokosuka Naval Arsenal was attacked by one bomber during the Doolittle Raid on 18 April 1942 and by a large force of carrier aircraft during the Attack on Yokosuka on 18 July 1945. The facilities were seized by the Allied forces at the end of World War II, and on 15 October 1945 the Yokosuka Naval Arsenal was officially abolished.
“However, the facilities continued to be used in the post-World War II period, by the United States Navy as the Yokosuka Ship Repair Facility and its former property is now under the control of the United States Fleet Activities Yokosuka.”