was one of four principal naval shipyards owned and operated by the Imperial Japanese Navy, and was located at Yokosuka, Kanagawa prefecture on Tokyo Bay, south of Yokohama. History 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. The construction of the arsenal was an important first step for the modernization of Japan's industry. Modern buildings, an aqueduct, foundry, brick factories, technical schools to train Japanese technicians were established. After the Boshin War and 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. 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, and the Yokosuka Shipyards was renamed the Yokosuka Naval Arsenal in 1903. Japan had purchased five submarines from the American Electric Boat Company during the Russo-Japanese War of 1904–1905. These Holland Type VII submarines were built by Arthur Leopold Busch as he traveled to Japan during this time. Mr. Busch was a naval architect and shipbuilder who represented the newly organized company (Electric Boat Company) now located at the Quincy Massachusett's shipyard known as the Fore River Ship and Engine Company. These first five submarines became Japan's (IJN) initial entry into the theater of underwater warfare that began nearly the same time as the outbreak of the war. Another representative of Electric Boat, Frank Cable, an electrician working for Isaac L. Rice's company trained two Japanese crews in the operation of such craft. Arthur Busch was also the man responsible for building the United States Navy's first submarine some five or so years before this time for the Holland Torpedo Boat Company. This (particular craft) was named the and was America's first commissioned craft (of this) type. Two additional Holland-designed submarines were built for Japan by 1906 "under contract" and a licensing "agreement" with Holland's company back in 1905. These pioneering submarines progressively got larger and larger as time went on, climaxing (in size) by the