had many names, each depending on the period of its existence, and the circumstances at that time. Many of the names were acronyms that were derived from its military name or designation, which changed from time to time. The arsenal was sometimes known as "Kūgi-shō" (空技廠, a contraction of "Kōkū Gijutsu-shō" 航空技術廠). The name Yokosuka prevailed however, even though it referred to the Arsenal's location at Yokosuka, Japan. History The air arsenal's roots go back to 1869 when the Imperial Japanese Navy (IJN) established a naval arsenal at Yokosuka, about 13 miles south of Yokohama on Tokyo Bay. The arsenal provided ship building, repair and replenishment to the Japanese Navy. It was also a storage depot where munitions and other assorted supplies were brought as they were purchased. When a number of foreign aircraft were purchased for evaluation, the Navy brought them to the arsenal for processing. The arsenal assembled the aircraft from their shipping boxes, and when assembled, they were flown by the pilots who had been sent abroad for flying lessons and evaluate the aircraft flown. Modifications to these aircraft were done as weaknesses were found, or when an improvement was incorporated. To facilitate this work, the IJN established the Aeroplane Factory, Ordnance Department at the arsenal's torpedo factory in May 1913. The next year, the first acronym was used was Yokosho, a contraction of . The arsenal was renamed in December 1919. The name was assigned by April, 1923, when the arsenal was moved to Tsukiji with several other Naval support units. The entire Tsukiji facility was destroyed in the 1923 Great Kantō earthquake. Several names were used when the navy began establishment of the arsenal. Research was started again in 1924 when several aircraft were evaluated. Under the command of the newly formed Naval Air Headquarters, the was formed at Yokosuka on 1 April 1932. A large amount of draftsmen and Designers were transferred from the Hiro Naval Arsenal, ending aircraft production there. The war years During World War II, the arsenal was responsible for the design of several IJN aircraft, although the arsenal itself did not manufacture more than a few prototypes of the aircraft it designed. Its designs were mass-produced by companies such as Aichi Kokuki, Watanabe Tekkōjo steel foundry, (renamed in 1943 to ), and the . Aircraft designed by the arsenal are usually designated by the manufacturer's letter "Y" for "Yokosuka". An