Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range

A Proving Ground for Torpedoes on Katashima

The Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range (旧佐世保海軍工廠川棚魚雷遠距離発射場) is the site of an Imperial Japanese Navy torpedo test range on Katashima in Mitsukoshi-go, Kawatana, Nagasaki Prefecture; completed in August 1918, five of its structures were registered as Registered Tangible Cultural Properties of Japan on August 15, 2024. Locally it has long been called the Katashima Torpedo Launch Test Site (片島魚雷発射試験場跡), and today it sits inside the town's Katashima Park.

This was where finished torpedoes faced their final exam. Weapons built at the Sasebo Naval Arsenal and at Mitsubishi's Nagasaki ordnance works were brought here and fired for real, from an artificial island out across Omura Bay. Inspectors measured speed, drift off the aiming line, time to surface, and how much fuel and compressed air each run consumed. Only torpedoes that passed were shipped to the Sasebo Naval District. The rest were adjusted and fired again.

A volunteer guide handbook published by Kawatana Town preserves the recollection of a student laborer assigned here in the spring of 1945. Tests ran roughly once every four days to a week, he recalled, with about eight torpedoes fired in a day and perhaps three passing.

Omura Bay touches the open sea only through two narrow channels, the Hario and Haiki straits, and its water is unusually calm. For a range built to send a torpedo straight and far, that calm was the whole point.

From Tategami to Ei-no-hana to Katashima

Torpedo testing for the Sasebo Naval District began modestly in 1895, with a wooden pier off the tip of Tategami point. In 1902 a new range with a 4-kilometer reach opened at Ei-no-hana, a promontory south of Sasebo harbor.

After the Russo-Japanese War, ship traffic in and out of the harbor grew heavy enough to make firing inside the port dangerous. At the same time the navy developed torpedoes that could run more than 10 kilometers, which a 4-kilometer range could no longer test. In 1916 construction began on Katashima, in the northern corner of Omura Bay, of a range capable of shots up to 15 kilometers. Partway through, the project was renamed from a "long-range torpedo test range" to a "long-range torpedo firing range," the name it still carries.

At first, three lookouts watched each run: one on the summit of Katashima, one on Takashima about 6 kilometers away, and one at Kazehaya about 8 kilometers away. All were small single-story timber huts. Sighting markers for the range were finished in March 1919, and full operations are thought to date from around then. In 1925 the Katashima lookout was rebuilt in brick and reinforced concrete and renamed the Observation Post.

Between 1938 and 1942 the range was expanded with new torpedo adjustment halls and tunnels. In 1942 the Kawatana Naval Arsenal opened about 2.5 kilometers to the northeast, and the strait separating Katashima from the mainland was filled in, which is why the former island is now joined to land. The Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range stayed in use until the war ended in 1945, when floors, stairs and many openings in its buildings were destroyed.

How Five Structures Came to Be Registered

After the war the site was left largely untouched for decades. The push to protect it started in 2019, when the town assembly raised the question of preservation. National cultural officials inspected the site in 2020, and in 2022 all five structures were surveyed with 3D laser scanning. The application went in during October 2023, the Council for Cultural Affairs recommended registration on March 15, 2024, and registration followed on August 15. The five registration numbers run consecutively, from 42-0141 to 42-0145.

The case rests first on concrete. These are structures from the very beginning of concrete engineering in Japan. The artificial island and the jetty were both built by stacking precast concrete blocks, a method used earlier for the old Akasaki quay wall in Sasebo. Kawatana's preservation plan regards this as probably the first time the technique was applied to an artificial island and an arched bridge.

The second strand is architectural lineage. The Hario Radio Transmitting Station in Sasebo, completed in 1922, has a stone oil store strikingly like the one here. The Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range was finished four years earlier, evidence that engineers across the Sasebo Naval District were working from a shared design vocabulary.

Kawatana adopted a formal preservation and use plan in March 2026. In the century and more since 1918, none of the five structures has undergone major repair, and the plan lists repairing the concrete doorway frame that spalled in 2024 and treating exposed, rusting rebar among its first tasks. The registration plaque sent by the Agency for Cultural Affairs is on display at the counter of the Kawatana Central Community Hall.

Finding Your Way Around Katashima Park

Most of the Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range clusters along the west shore of Katashima. Walking in from the parking area, the first thing you meet is a tall walled shell with a stone lower story and brick added above: the Machine Room and Torpedo Adjustment Room. A small stone oil storehouse stands just to its south.

From the front of the machine room, the jetty strides out to sea on five low arches, linking the shore to the firing platform about 50 meters offshore. The platform is a rectangular artificial island with a three-story tower at one end. The Observation Post hides in the trees on the island's southern summit; look for the triangular window jutting out toward the sea.

Other remains share the park: two torpedo adjustment halls added between 1938 and 1942, two tunnels bored north to south through the island, and a sonar test station. None of these is registered, though the town's plan treats them as part of the same historic whole.

Paths are uneven and slick after rain. Signs close the entrance to the firing platform and the path to the sonar test station because of fall and rockfall risk, and the machine room is fenced off. Please stay out of marked areas.

Visiting and Getting There

The Former Sasebo Naval Arsenal Kawatana Long-Range Torpedo Firing Range is open as Katashima Park, and there is no admission fee. No staff are stationed on site, so for guidance contact the Kawatana Town planning and tourism section (0956-76-8335) in advance; the town's volunteer guides for wartime sites also lead tours.

A car makes the trip simple. The park is about 10 minutes by car from Kawatana Station on the JR Omura Line and has free parking for 10 cars. The town notes that the site cannot be reached by the seaside road, so double-check any navigation route. Kawatana Station is about an hour from JR Nagasaki Station by rapid train, or about 11 minutes from Huis Ten Bosch Station. From Nagasaki Airport, Saihi Bus limited express services reach the Kawatana stop in about 40 minutes.

Film shoots and other planned photography require an application to the Kawatana town office. The ruins served as a model for scenes in the animated film "The Boy and the Beast" and as a main location for the feature film "Inori," so photographers come often. If you are unsure whether your own snapshots need permission, a quick check with the town settles it.