Ōga Kaiten Replica
Hiji Town  , Ōita Prefecture
Ōga was the fourth and last kaiten human torpedo base that was constructed by
the Japanese Navy in the latter part of the Pacific War. In 2014, the Hiji Town government
implemented several improvements to the former Ōga Kaiten Base area where
there still remains more than ten kaiten-related facilities on the former base
premises, including underground tunnels to store kaiten and a ramp to transfer
kaiten to the sea. The centerpiece of the improvements is a
full-size kaiten replica that was put on display in front of the base's torpedo
adjustment pool. The local government constructed a large parking lot to
accommodate visitor buses, a rest area, and a public restroom.
This historical site excels in information provided about its historical
significance. A free six-page color brochure in Japanese is available to a
visitor. The brochure has a detailed map of base structures, including
photographs of those that still remain. There is also a large information
signboard with the following information (translated to English) and a map of
the former base.
Historical Background and Kaiten
On December 8, 1941, the Japanese Navy attacked Pearl Harbor at Hawaii's
Oahu Island, and the Pacific War began. When the war started the Navy was
dominant but shifted to the defensive after the loss in the sea battle off
Midway in the North Pacific. Finally, a loss at Okinawa was expected, and
air bombardment of Japan's home islands began. As Japan's Navy was in an
unfavorable situation, several hundred Type 93 torpedoes dormant in weapon
arsenals were modified and employed as human torpedoes that would be steered
by a person to make taiatari (body-crashing) attacks against enemy
ships. Four kaiten training bases were opened at Ōtsushima, Hikari, and
Hirao in Yamaguchi Prefecture and Ōga at Hiji Town in Ōita Prefecture. This
human torpedo was named "kaiten" with the meaning of "turn the heavens and
reverse the war situation."
Base's Full Details and Ōga Totsugeki  Unit
The facilities of this base were expedited in strict secrecy due to the
war situation and defensive reasons. They were constructed adjoining the
fishing port in Ōga, where Beppu Bay could be used as a training area and
where it was geographically superior at the time of a sortie. The base
facilities included 51 structures such as the Kaiten Jinja (Shrine), kaiten
storage structures, torpedo adjustment shop, transformer substation, and
water purification plant. Two thousand men were assigned to the base. The
"Ōga Totsugeki Unit" with some 285 kaiten pilots was formed on April 25,
1945. In the same year on August 3, there was the only sortie from this
base. Eight pilots and maintenance workers with eight kaiten advanced to
Mugigaura on Sukumo Bay in Ehime Prefecture. On August 12, they received an order to stand
by to sortie, but the war ended on August 15 without a sortie.
On August 25, the Ōga Totsugeki Unit disbanded. The base was handed over to
the American military on August 31. After that, kaiten that remained were
scrapped. On this base after the war's end, Ensign Shūsuke Matsuo committed
This location of 25 hectares that was Ōga Kaiten Base is nearly all
privately-owned land. Cooperation with these individuals is necessary in
order to maintain and preserve it in the future.
Hiji Town maintains and preserves the tunnels, torpedo adjustment pool,
transformer substation, and water purification pool that remain at present.
The town wants to communicate to future generations that a tragic war should
never be repeated.
On April 24, 1975, the Ōga Kaiten Association was founded by former unit
members. April 25, the date when the Ōga Totsugeki Unit originally was
formed, was set as the date of the regular festival that is held each year.
We will be pleased if everyone who visits this place will realize
personally the preciousness of people's lives and the blessings of peace.
Human Torpedo Ōga Kaiten Base Site Monument
On the road approaching the kaiten replica there is the above monument with
the engraved words of "Human Torpedo Ōga Kaiten Base Site Monument." The
monument's base has a plaque with the following words:
Turn the heavens hoping to reverse the war situation.
Donated by Hiji Lions Club
Former kaiten storage tunnel
The information sign directly in front to the kaiten replica has the
Length: 14.75 m, Diameter: 1.0 m, Total weight: 8,300 kg
Maximum speed: 30 knots (about 56 km/hr), Cruising time: 2 hours, 15 minutes
(at 12 knots)
Warhead weight: 1,550 kg, Crew: 1 man
On April 25, 1945, Ōga Kaiten Training Base opened. From May 23
training started in the training area in Beppu Bay. In the training the Type
1 Mod. 1 kaiten, which was an improved version of the Type 1, was used. The
most significant differences compared to the Type 1 were a modified shape to
better cut through waves
and the ability to make a sortie from land without a hatch on bottom to
enter from a submarine . On August 3 near the war's end, there was the only sortie from Ōga
Base. Eight Type 1 Mod. 1 kaiten and eight men went through dangerous seas
and made it safely to Mugigaura on Sukumo Bay in Ehime Prefecture. They
received an order to stand by to sortie, but while on stand-by the war
Information signboard with map of Ōga Kaiten Base
To the right of the kaiten replica there is a small monument to remember
those who contributed to the creation of the display. The inscription reads:
Monument Honoring Human Torpedo "Kaiten" Replica Creation
This location was a kaiten training base. Base preservation activities
are carried out to communicate to future generations the tragic war history.
The creation and set-up for display of a full-size kaiten
replica has been accomplished through the support of volunteers in the area.
Here we express our gratitude by recording the names of persons from whom
great cooperation was received.
Heiseikai Medical Corporation
Kiminori Sakai, Chairman
Shōwa Kensetsu Kōgyō
Kensaku Endō, Chairman
Shōjirō Matsumoto, Representative Director and President
Yoshimi Kudō, Hiji Town Mayor
Kaiten replica next to former torpedo adjustment pool
The Ōga Kaiten Shrine on the
grounds of Sumiyoshi Shrine is located a short distance from the kaiten replica
on the top of a hill overlooking the bay.
1. Ōga Village was merged into Hiji Town in 1954.
2. The word totsugeki means "charge" or "assault" in Japanese.
3. The hatch for the Type 1 Mod. 1 kaiten was on
top rather than bottom.