The Osaka Arsenal was a state weapons factory of the Imperial Japanese Army in Osaka during the period from 1870 to 1945. In the Meiji period, the self-supply of the armed forces with modern weapons was a high concern for the government. The Japanese military leader Ōmura Masujirō proposed to build a garrison with gun and ammunition production facilities at Osaka Castle. The central location of Osaka favored transport routes over land and water. Although Ōmura was the victim of an attack in November 1869, his proposal was nevertheless accepted.