Kawatana Naval Arsenal (Branch of Sasebo Naval Arsenal)

Kawatana's connection with naval torpedoes dates from the Taishō era. In 1918 the Sasebo Naval Arsenal (佐世保海軍工廠) built a long-range torpedo firing range on Katashima, off Kawatana Town on the north shore of Ōmura Bay in Nagasaki Prefecture, using the calm inland waters to test-fire and inspect every torpedo made by the arsenal and by Mitsubishi's Nagasaki Ordnance Works before delivery to the fleet. The surviving Taishō-period observation post, firing platform, jetty, oil store, machinery room and torpedo adjustment room are registered tangible cultural properties under the name "Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range".

The Kawatana Naval Arsenal (川棚海軍工廠) was established as a branch facility of the Sasebo Naval Arsenal in Kawatana Town. As demand for aerial torpedoes rose, the facility experienced major expansion and modernization in 1938–39; a branch factory was then built on reclaimed land along the shore and was raised to an independent naval arsenal during the Pacific War. Sources differ on the exact years, giving 1942 or 1943. Specialized in torpedo production, the arsenal mass-produced the Type 91 aerial torpedo — the family of weapons used at Pearl Harbor — and other underwater ordnance for the Imperial Japanese Navy.

By 1944, to protect production from American air attacks, work was dispersed into tunnels dug into nearby hillsides. This site's earlier text states that school children were mobilized to excavate 16 tunnels, while Kawatana Town records speak of more than twenty dispersal tunnels, seventeen of them confirmed today. It is also reported that U.S. Army Air Forces target maps misidentified the arsenal as a beer factory and that it was never bombed; this claim needs further verification. Kawatana also housed a temporary torpedo-boat training station where crews of motor torpedo boats and Shin'yō suicide boats were trained, commemorated today by a memorial.

After the Nagasaki atomic bombing on August 9, 1945, the naval facilities at Kawatana were used to house and treat atomic bomb survivors evacuated from the city. The arsenal was abolished after the war and its grounds turned over to private factories and housing. The Katashima test range, maintained by the town as a park, is the most complete surviving site for understanding how the Navy produced and tested its torpedoes.