Ozushima : Kaiten's Last Sanctuary

Kaiten Type 1 replica, Kaiten Memorial Museum.

Towards the last years of the Pacific War, with its once powerful Imperial Japanese Navy ( IJN ) close to total annihilation and its maritime supply lines strangled by the unrestricted submarine warfare waged by the US Navy, the Japanese high command resorted to the deployment of various types of suicide weapons in a desperate but futile attempt to reverse the fortunes of war. One of those so called special attack weapons was the Kaiten, also known as the human torpedo, the underwater equivalent of the Kamikaze.

Despite the high human cost, the Kaiten only achieved limited success throughout its short operational history and was largely forgotten after the War. Of the several hundred operational as well as prototype Kaitens produced, only a handful were ever preserved and displayed in museums in Japan and the United States. Fortunately, at least two former Kaiten training bases at Ozushima and Oga escaped the fate of demolition and are today heritage sites where visitors can learn about the tragic history of those special attack units. Between them Ozushima is better known for its Kaiten Memorial Museum and the ruins of the torpedo launching facility.

I visited Ozushima on a cold rainy winter's day on 7th December 2018* and discovered a quiet and desolate island with hills overlooking the surrounding Seto Inland Sea. A somber and sad place befitting to be the last sanctuary of the Kaiten .....

Kaiten In A Nutshell

The Kaiten was essentially a suicide submarine created by modifying a heavy weight torpedo, inserting a compartment to accommodate a human operator to the mid-section and enlarging the warhead. Several could be carried onboard a mothership, usually a fleet type submarine, and they would be launched when a worthwhile enemy vessel was within range. The Kaiten operator would steer his suicide craft underwater towards the target and pop up to periscope depth for a mid-course correction before the final high speed intercept run. It was the brainchild of two naval lieutenants Kuroki Hiroshi and Nishina Sekio.

Kaiten ( 回天 ) literally meant return to the sky or return to heaven but its original meaning in Japanese as envisaged by Kuroki pertained to the reversal of the will of heaven and regaining the edge on the battle front. It was Vice Admiral Omori Sentaro, then director of the Special Attack Division, who named the weapon after the Kaiten Maru ( 回天丸 ), a steam-powered warship which once served in the navy of the Tokugawa shogunate in the final years of the Edo period. The project was top secret and was given the code name Maru Roku Kanamono ( ㊅金物 ), which roughly translates to zero six hardware.

Key to the construction of the Kaiten was the Type 93 ship launched high-speed wakeless torpedo which used compressed oxygen ( instead of air ) as its propellent. Known as the Sanso Gyorai ( 酸素魚雷 oxygen torpedo ) and nicknamed the Long Lance torpedo by western media, it had a high explosive warhead weighing 490kg and was the most advanced torpedo of its time.

Conceptualized as a special attack weapon in late 1943 and approved for trial production by the naval high command in Feb 1944, Kaiten prototypes were quickly tested and readied for mass production by July 1944. That same month special Kaiten base units were also setup and the first Kaiten training base at Ozushima was operational by 1st September. More training bases were subsequently built all over the coastal areas of the Seto Inland Sea and also around Kyushu Island.

The first combat operations took place in Nov 1944 where Kaiten units of the Kikusui strike group successfully sunk the fleet oiler USS Mississinewa at Ulithi Harbour, Caroline Islands. The only other successes were the sinking of an infantry landing craft in Jan 1945 by the Kongo group and the destroyer escort USS Underhill in July 1945 by the Tamon group.

Of all the Kaiten variants, only the Type 1 saw combat operations. Type 2,4,5,6 and 10 only existed as prototypes and were never used operationally. The Type 10 was developed with coastal defense in mind and was the only variant based on the lighter Type 92 torpedo.

In Japanese, the term ningen gyorai ( 人間魚雷 ) or human torpedo, is synonymous with the Kaiten special attack weapon. In fact they are frequently combined like an adjective before a noun - the human torpedo Kaiten ( 人間魚雷回天 ).






Kaiten ( Maru Roku Kanamono Type 1 )
Displacement 8.3 tons Length 14.75m Speed 30 knots
Engine Power 550hp Warhead 1.55 tons
Source:  Kaiten Museum



Where In The World Is Ozushima?

Ozushima ( 大津島 ) is a Y-shaped island lying approximately 10km off the coast of Shunan City in Yamaguchi Prefecture of Japan. Granite extraction and export used to be the main industrial activity providing sustenance to the island. Endowed with sheltered bays which form natural ports and surrounded by shallow seas, it was here that the Imperial Japanese Navy chose to set up its torpedo testing facilities in 1937 and subsequently the first Kaiten training base in 1944. The base infrastructure included command buildings, living quarters, mess hall and kitchen, guard houses, clinic and sickbay, maintenance workshops, storage areas, seaplane hangars, gun placements and bunkers. Several of these military structures including the torpedo testing pier and the hilltop torpedo observation post survived to this day, though in various degrees of dilapidation. In the post-war years a Kaiten monument was erected on a hill overlooking the former base. The Kaiten Memorial Museum was later built adjacent to the monument. It has a collection of more than a thousand artifacts relating to the Kaiten. Today, with the demise of its granite industry and a greying and declining population**, Ozushima markets itself as Kaiten Island, with the hope to lure in tourists keen to discover the obscure history of the Human Torpedo.

Ozushima and Shunan City

Ozushima Kaiten Base. Existing relics 1 Kaiten Museum 2 Stairs of Hell
3 Torpedo Ignition Test Site 4 Hazardous Material Storage
5 Transformer Station 6 Seaplane maintenance area entrance
7 Torpedo observation station 8 Tunnel 9 Torpedo Launching Facility.

Tokuyama Ferry Terminal : Gateway to Ozushima

To get to Ozushima, you will have to find your way to the Tokuyama Ferry Terminal in Shunan City which fortunately is within walking distance from Tokuyama Station, accessible by the Shinkansen bullet train. Return tickets cost ¥710 ( US$6 ) and it takes about 18 minutes to reach the island by the fast ferry.

The ferry terminal is difficult to miss as there is a replica of the Kaiten prominently displayed at the entrance to the parking area. This life sized replica was used to film the Kaiten movie Deguchi no nai umi or The Sea Without Exit in 2006. It looked and felt like the real thing, black, metallic and menacing, complete with the emblem of the Kikusui strike group on both sides of the flow deflector next to the periscope. I could have been fooled if not for the information inscription in front of the Kaiten.

However, instead of just placing the replica next to an ugly old building by the road side in a restrictively narrow area, the Kaiten could have been better displayed on its own perhaps in a small park next to the ferry terminal.

Kaiten Type 1 life-sized replica, Tokuyama Port, Yamaguchi. 

Kaiten replica with Toyoko Inn Tokuyama
and Shinkansen Station in the background.

Inscription explaining the origins and purpose of the Kaiten replica.
 It was used in the 2006 movie Sea Without Exit.

Kaiten Island

The moment you set foot on Ozushima, you would notice that it is extremely quiet with hardly a soul in sight. The single asphalt road that leads away from the pier is almost devoid of vehicular traffic. There is no bus or taxi service on this small island. A huge sign proclaims Ozushima the Island of Kaiten ( 回天の島 kaiten no shima ) and a map at the bottom lists the various points of interest on the island.

Ozushima from the ferry pier.
The building with the green roof marks the site of the former Kaiten base.

Sign reads Welcome to Otsushima - Kaiten Island

Just by the roadside near the Kaiten Island sign is a small monument with the statue of the Buddist goddess Kannon ( 観音 ) and the words Kaiten memorial ( 回天供養 kaiten kuyo ). A small donation box is prominently placed directly in front of the goddess statue. Fresh chrysanthemum flowers adorning the monument indicates regular upkeep by the islanders. I am guessing that Kannon, being the Goddess of Mercy and also being regarded by the people of coastal East Asia as Goddess of the Sea, the protector of fishermen and sailors, must have been the patron saint of the Kaiten operators, perhaps even the entire Japanese Navy.

The roadside Kaiten memorial with the statue of the sea goddess Kannon.

Behind the statue of the goddess and carved into the stone wall are the lyrics of two songs commemorating the Kaiten and the deeds of its operators, " Mother of Kaiten - Human Torpedo " by composer and singer Utagawa Fumiko ( 回天の母～人間魚雷～ ) and " Peace Kannon Folk Song " by Aoyama Rumi ( 平和観音音頭 ). The lyrics of Utagawa's song is also found on the polished stone slab erected beside the Kannon statue.

Lyrics of Utagawa Fumiko's Mother of Kaiten - Human Torpedo
 is found on this stone slab and on the wall behind it.

Lyrics of the Peace Kannon folk song by Aoyama Rumi
on the wall behind the Kannon statue.

I follow the signs and head towards the Kaiten Memorial Museum which should be less than a kilometer from the ferry pier. The path goes past the Ozushima Fureai Center, a campground of sorts but it is understandably empty at this time of the year. It then goes behind a couple of school buildings which are also quiet and unoccupied. A large empty grassy field can be seen beyond the school compound. I will soon learn from a signboard by the path that this is the actual site of the former Ozushima Kaiten Training Base. A long concrete high wall which separates the footpath from the site of the former base still stands to this day. It served to prevent Ozushima islanders from observing the activities on the base when they are walking past the area during the war years.

Ozushima Elementary School was built at the site of the former Kaiten base
 after the War. In its last year of operation in 2015, the school had
only 1 student, 3 teachers and 1 staff member.

This structure beside the main school building is probably the
assembly hall. The field where the torpedo maintenance shed
once stood can be seen in the background.

This school field was the site of the main kaiten base.

 

The partially sealed hazardous material storage area is seen built into the cliff side.
The small structure to the right of the school hall is the old transformer station.

Signboard compares former and current structures where the kaiten base once stood.



Passageway lined with sakura trees leading to Kaiten Museum.
The atmosphere will be very different by late March and early April.

The footpath then becomes steep and ends up at the top of a low hill where the Kaiten Memorial Museum is located. Two granite columns mark the entrance to the long passageway leading to the museum. On both sides of the pavement are two neat rows of stones bearing the names of the deceased Kaiten operators.

A large bronze bell with a long striker can be seen hanging from a shelter in front of the museum building. This the Bell of Peace Prayer ( 平和祈念の鐘 Heiwa Kinen no Kane ). A plaque on the outward facing side of the pillar proclaims it was constructed in 1974 with donations from the Lions Club of Tokuyama. Another plaque on the inward side directly facing the bell bears even more interesting information, all in Japanese only, as usual. It states that the material used to cast the bell included about 100kg of gunmetal ( 砲金 hokin ) from the cartridge cases ( 薬莢 yakkyo ) salvaged from the number 3 turret ( 三番砲塔 sanban hoto ) of the IJN battleship Mutsu ( 陸奥 ). The Mutsu sunk with the loss of 1121 lives after suffering a mysterious internal explosion in the very same turret while moored at the Hashirajima fleet anchorage in June 1943. The anchorage lies within the Inland Sea about 60km east of the Kaiten museum as the crow flies. The bell has a diameter of 90cm, weighs 850kg and is crafted after the famous Uji Byodoin Bell of Kyoto, with embossed designs of celestial figures, lions and Chinese-styled words. On 15th August every year, the anniversary of Japan's surrender during World War II, the bell would be struck by visitors with the hope that the sounds would bring peace to the world and appeasement to the lost souls in the southern seas.



Bell of Peace Prayer with Kaiten monument and Kaiten replica
 in background and ginko leaves.

100kg of gunmetal : The link with Battleship Mutsu

The Kaiten Monument

Behind the Bell of Peace Prayer lies the Kaiten Monument, a monolithic greyish granite structure of about 2 meters in height with an altar in front of it and flanked on both sides by stone slabs carved full with words. The plaque on the left lists the submarines lost or sunk during Kaiten operations giving details such as vessel name, operating base, departure date, wreckage site, captain's name and numbers of sailors who perished with the submarine. For example the last entry read : I-165 Submarine, departed Hikari Base 15th June 1945, lost east of the Marianas, captain Ono Yasushi with 104 crew members. Of the 32 submarines involved in Kaiten operations, 8 were lost. The plaque on the right bears the names of all the Kaiten operators who had lost their lives during training or actual combat.

Kaiten Monument



Kaiten Monument overlooking the Seto Inland Sea.

List of submarines and submariners lost during Kaiten operations 

 

List of 145 Kaiten operators and maintenance personnel
 killed during operations or training.

The location of the monument is almost at the edge of a cliff overlooking the Shin Ozushima Ferry Terminal, its breakwaters and the Seto Inland Sea beyond. By this time of the year the trees have mostly shed their leaves leaving bare branches pointing forlornly skywards. The cloudy and rainy weather helps make an already bleak atmosphere even more depressing. I wonder if this despondent feeling was how the Kaiten operators felt before their final departure from Ozushima.

View of the bleak Inland Sea and leafless sakura tree
on a cold winter's day from behind the Kaiten Monument.



Kaiten Type 1 Replica

A life-sized Kaiten Type 1 replica can be seen next to the Kaiten Monument in front of the museum building. Just like the replica at Tokushima Ferry Terminal, it features the emblem of the Kikusui strike group on its flow deflectors. The fact that the Kaiten Museum does not even have a real Kaiten specimen and has to rely on a replica for display is telling of the very small numbers that were preserved after the War. Then the priority was the de-establishment of the armed services, disarming, demobilization and repatriation. Probably very little thought or room was left for the preservation of war relics and anything that could be scrapped would be scrapped. After all, much raw materials were required for the reconstruction and rehabilitation of a war torn nation. By the time the Japanese society has again prospered and the trauma of war has somewhat faded to the extend that the general populace can embrace the idea of commemorating the war dead, most of the artifacts are already lost or forgotten.

As far as I am aware, the only complete Kaiten specimens in Japan can be found in the Yushukan War Museum of the Yasukuni Shrine ( Type 1 ) and the Kure Maritime Museum a.k.a. Yamato Museum (  Type 10 ). In addition, Yushukan has the hull of a Type 4 and the History and Folklore Museum of Yamaguchi has the hull of a Type 2.




Kaiten replica and sakura tree next to monument



Kaiten replica with museum courtyard behind



Kaiten replica with museum behind

The Kaiten Memorial Museum

The idea of a memorial museum was first mooted in 1962 during a kaiten interest group meet in Tokyo. The intended purpose of the museum was to collect, preserve and display artifacts belonging to the deceased kaiten operators. Funding campaign for the construction of the museum began in 1965 and a total of 19.62 million yen was collected. The museum opened its doors in Nov 1968.

Among its collections were more than a thousand items including letters, last wills, photographs and uniforms. One of the most remarkable exhibit was a replica of Kuroki and Higuchi's last testament written on the inner wall of their sunken kaiten before they died of asphyxiation from oxygen depletion. It was a routine training mission on the evening of 6th Sep 1944 that went terribly wrong with the Kaiten stuck in the muddy seabed after an unexpected dive. Trapped under 18 meters of water without much hope of being rescued, the two officers were giving a detailed account of what went wrong and were even suggesting improvements for subsequent models. The sunken kaiten was only located the next day by which time both officers were dead. Kuroki was four days from his 23rd birthday.

Replica of Kuroki and Higuchi's last testament.
Source : Kaiten Memorial Museum

After 30 years in operation, the museum underwent a major renovation in 1998 at a cost of 47.33 million yen. A section of the Kaiten hull used to film the 2006 Kaiten movie Deguchi no nai Umi is displayed in front of a wall full of photographs of deceased Kaiten pilots. Because the museum has a no photography policy, I did not take any photographs when I was inside the museum.

The normal entrance fee is JPY300 ( about US$3 ) for adults but the museum will waive admission fee on two occasions every year. The 15th of August is the anniversary of the surrender of Japan during WWII and on this day visitors will strike the Bell of Peace in the museum's courtyard. Also on the second Sunday of  every November where a memorial ceremony is held in front of the Kaiten Monument. In recent years the number of visitors to the museum hover between 12000 to 16000 annually.

Admission ticket to Kaiten Museum dated 2018 Dec 7th.

Kaiten Tunnels And Launching Pier

Apart from the Kaiten Memorial Museum, the other major attractions of Ozushima are the ruins of the torpedo testing and kaiten launching pier as well as the tunnels that connect it to the main base.

By 1937, weapons engineers producing the Type 93 Long Lance torpedo at the Kure Arsenal had wanted better test facilities to replace the existing one at Dainyu. Ozushima was selected because it could provide a wider and longer test range. The pier to launch the torpedoes was made of steel reinforced concrete and was completed in 1939 at a cost of 830000 yen. It has 2 levels with cranes and 2 launch bays. Construction of its foundations required the use of 8 caissons and another 5 for the foundations of the passageway. The main structure has a height of 10m, length of 12m, width of 7.5m and a draft of 7.5m. Its estimated weight was 700 tons. Before the tunnels were built, portions of the coastal cliffs were hacked away to build a path over rocky outcrops so that the torpedoes could be hauled to the pier from the maintenance workshops. Construction of the tunnels with rail tracks made the transfer much easier.

The tunnel measure about 250 meters and the entrance is not far from the Ozushima Elementary School. At present the rail tracks have been paved over and even the walls of the tunnel looks coated very neatly with fresh concrete. At the mid-point the tunnel widens and has a side opening to the sea where the Kaiten launching pier could be seen not far away. This section of the tunnel also has old photographs of the Kaiten and its operators and audio explanations of the Kaiten's history. The tunnel ends in front of the Kaiten launching pier and a concrete connecting path brings the visitor to the pier.

The tunnel entrance.

Rail tracks are paved over. Wall have been replastered.

Side opening to the sea

Seaward view of tunnel side opening

Mid-portion of tunnel with photo gallery

Tunnel exit and link way to the Torpedo Launching Pier.

The Kaiten base at Ozushima was officially opened on 1st Sep 1944 and training commenced just 4 days later. The torpedo launching pier was then used to launch Kaitens for their training practice in the sea. The internal torpedo launching bays within the structure were designed to accommodate the Type 93 torpedo with a diameter of 61cm. They were too narrow to launch the kaiten which had a diameter of 1 meter. Instead, the kaitens were hoisted into the water from the side of the concrete pier by cranes. The rusted remnants of such a crane can still be seen at the edge of the pier to this day. Note that embarkation for combat operations do not take place at this pier. Instead, other piers over at the main base were used.

Currently, the torpedo launching bays and the upper level of the pier are out of bounds and fenced up. A signboard explains about the Type 93 torpedo. A granite marker stands near the beginning of the link way to the pier and proclaims it the ruins of the torpedo launch site.

Because it is the only surviving structure for Kaiten training built during World War II in the whole of Japan, it is deemed a war heritage and it was conferred the Heritage Award by the Japan Society of Civil Engineers ( JSCE ) in 2006. Here is the JSCE explanatory note to its selection in Japanese.

Sign at exit of tunnel proclaims the area
the Torpedo Launching Facility Relic

The Type 93 Torpedo Launching Facility and Kaiten Training Relic

The two storey concrete structure with two launch bays behind the fence.

Signboard explains the origins of the torpedo test site

These bays are for launching the 610mm Type 93 torpedoes.
The Kaiten has a 1000mm diameter and would not fit.

Remnants of the foundation of the Kaiten hoist at the side of the pier

Torpedo Observation Station

On a hilltop overlooking the sea to the west lies the ruins of the torpedo observation post ( 魚雷見張所 gyorai miharisho  ). A fairly strenuous climb through a bamboo forest is required before reaching this site. It is a single storey building by the cliff with large windows to observe torpedo firing during the War. All its windows are now gone and only the window frames remained. The walls are bare and a few wires dangle from the ceilings, with the electric devices they power long gone. This ruin is generally quite free from graffiti and relatively clean.

Signboard explains about the torpedo observation station

Rear view of the dilapidated building 

The building has a commanding view of the surrounding seas

Bare, doorless and windowless but still standing after 8 decades.

An anti-aircraft gun placement site is located to the north of the museum but I did not have time to explore. It was supposed to have consisted of a 150cm search light, one single barreled 13mm anti-aircraft gun and 3 twin-barreled 12.7mm guns to provide the Kaiten base with some protection against air attack. It will have to wait for another visit to the island in the future.






I-58 with Kaiten Human Torpedoes on deck.
Box art from Tamiya.

The Legacy

The Human Torpedo Kaiten was a suicide weapon system unlike any other and unique to the Imperial Japanese Navy. It never quite achieved the success and notoriety of its aerial counterpart, the Kamikaze Special Attack. The only reason that it did not result in more deaths apart from the several hundred operators and submariners who died during combat operations was because the end of the War came swiftly. All Kaiten operations ceased by 15th Aug 1945 with the unconditioned surrender of Japan. Though they did not manage to turn the tide of war and save their country, the sacrifices of these young men may not have been entirely in vain so long as the message of peace is passed on to the future generations.

Today, 75 years on, the world might have forgotten about the Kaiten. However, in the quiet backwaters of the Seto Inland Sea, Ozushima continues to bear silent witness to this tragic legacy which happened so many years ago. Its schools might be closed, its population might be greying and dying, its industries might be gone, but here at Ozushima the Kaiten endures ...


* The day after my visit to Alley Karasukojima in Kure.
* 7th December is also the eve of the anniversary of the Pacific War to the Japanese because of time zone differences.

** In 2017 the population of Ozushima was 275. Of these 78.9% were above the age of 65.