⚓ Kaiten: Japan’s Human Torpedoes of World War II — A Complete Story

Kaiten: Japan’s Human Torpedoes  

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The Kaiten were a class of manned suicide torpedoes used by the Imperial Japanese Navy during the desperate final stages of World War II. Conceived as a naval version of the Kamikaze (Divine Wind) suicide aircraft, they represented the ultimate expression of the Japanese military's willingness for self-sacrifice to stem the tide of the Allied advance.

1. Origins: Desperation in a Losing War

By 1943–1944, Japan’s strategic situation had deteriorated badly. The U.S. Navy’s island‑hopping campaign was advancing rapidly, submarine blockades strangled supply lines, and Japan’s surface fleet was suffering catastrophic losses.

Amid this crisis, some naval officers proposed extreme measures to counter the overwhelming American naval forces.  

💡 Conception and Design

The idea for a human-guided torpedo originated in 1943 with two young Japanese naval officers, Lieutenant Hiroshi Kuroki and Ensign Sekio Nishina.

• Motivation: Following Japan's devastating naval losses, particularly at the Battle of Midway, they sought a weapon with the accuracy of a human pilot and the destructive power of a torpedo.

• Initial Reception: The proposal was initially rejected as too extreme. However, Kuroki and Nishina's persistence, including submitting a petition written in their own blood (a traditional Japanese show of sincerity, or makoto), eventually gained attention.

• Approval: After the catastrophic loss of the Marianas in June 1944, the desperate military leadership approved the project, dropping the initial requirement for the pilot to have an escape mechanism.

💡A manned torpedo, piloted directly into an enemy ship.

The concept promised:

• Precision guidance from a human pilot

• Greater chance of hitting fast-moving U.S. vessels

• Psychological and symbolic effect, similar to kamikaze aircraft

The name chosen was Kaiten (回天), meaning “Return to Heaven,” but also implying “change the world.”

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2. Design & Engineering of the Kaiten

The schematic of Kaiten

⚙️ The Type 1 Kaiten: A Modified "Long Lance"

The Kaiten's primary operational model, the Type 1, was a conversion of the formidable Type 93 Torpedo, famously known to the Allies as the "Long Lance." oxygen torpedo—the most powerful torpedo of the war—extended to include a cockpit, control system, and a self-destruct warhead.

Feature	Description
Warhead	~1,550–1,550 kg of explosives—massively destructive
Diameter	~1 meter
Length	~14–15 meters
Speed	30–40 knots depending on variant
Range	23–42 km
Guidance	Fully manual by pilot
Escape hatch	installed but nearly useless in practice

The semi-realistic cross section of Kaiten with pilot inside.

⚙️ Pilot Compartment

The pilot sat in a tiny space with:

• Periscope

• Gyro controls

• Rudder and depth controls

• Simple gauges for oxygen and fuel

• A trigger to detonate on impact

Officially, escape mechanisms existed, but no known pilot survived a mission—either due to design flaws or due to the mission’s suicide nature.

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3. Recruitment & Training: Volunteers in a Culture of Sacrifice

The Kaiten program specifically sought “volunteers,” though strong social pressure made refusal nearly impossible.

The young trainee soldier of Kaiten Pilot

 

⚙️ Training Bases

• Ōtsushima (near Hiroshima) — primary base

• Hikari Naval Base

• Tokuyama

⚙️ Pilots were typically:

• Young naval officers or cadets (often in their teens or early twenties)

• Highly trained and physically fit

• Ideologically motivated or compelled by duty

         Training was dangerous—multiple fatal accidents occurred during practice dives.

⚙️ Psychology of Kaiten Pilots

      A mix of factors motivated them:

• Bushido warrior culture

• Fear of shame if they refused

• Belief that sacrifice might save their country

• Propaganda promising honor and spiritual transcendence

    Many left farewell letters expressing both patriotism and sorrow for their families.

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4. Deployment: Submarine Platforms and Mission Challenges

The Kaiten were too slow and limited to launch independently, so they were carried by submarines, usually strapped externally to the deck. A typical submarine could carry 2–6 Kaiten.

⚙️ Operational Procedure

1. Submarine approaches enemy fleet silently.

2. Kaiten pilots enter their craft through underwater access tubes.

3. Torpedoes are released, and pilots begin their attack run.

4. Pilot uses periscope and manual controls to ram the target.

5. Explosion destroys both the Kaiten and (hopefully) the target ship.

⚙️ Danger was immense:

• Submarines carrying Kaiten were at risk of detection

• Rough seas often made launch impossible

• Kaiten engines often malfunctioned

• U.S. ships had strong anti-submarine defenses

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5. First Combat Success: USS Mississinewa (November 1944)

The first major success was the sinking of the American oiler USS Mississinewa at Ulithi Atoll on 20 November 1944.

A soldier inside the Kaiten is pointing a periscope at the battleship that is the target of the attack

A Kaiten from submarine I‑47 slipped into the lagoon. Witnesses saw:

• A sudden white spray

• A massive explosion

• Flames engulfing the tanker

• Over 60 U.S. sailors killed

This confirmed the weapon’s potential—but such successes were rare.

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6. Later Operations and Declining Effectiveness

Japan continued to deploy Kaiten in 1945 from several submarines including I‑36, I‑47, I‑56, I‑58, I‑361, and I‑370.

The Chief of Staff's Kaiten Battle Planning

⚙️ Notable Missions

February–March 1945: Off Ulithi Again

Multiple attempts were made, but U.S. patrols and defensive nets made infiltration nearly impossible.

I‑58 and the Sinking of USS Indianapolis (30 July 1945)

There is debate, but the consensus is that I‑58 sank Indianapolis with conventional torpedoes, not Kaiten.
(Some Japanese wartime records claimed Kaiten use, but the sub commander later clarified otherwise.)

High Failure Rate

Of all Kaiten launched:

• Many malfunctioned

• Many missed their targets

• Most pilots died with no damage inflicted

• Submarines carrying Kaiten were frequently sunk

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7. Human Cost

⚙️ Pilot Deaths

Approximately 100–125 Kaiten pilots died:

• In combat operations

• In training accidents

• In submarine losses

⚙️ Submarine Crews

Entire crews of several submarines perished while carrying Kaiten:

• I‑361

• I‑370

• I‑368

• I‑44

• Others damaged or lost

These losses alone surpassed any strategic gains.

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8. End of the Kaiten Program

By mid‑1945, Japan faced defeat, fuel shortages, and collapsing infrastructure. Air kamikaze attacks were far more destructive and easier to deploy. The Kaiten program continued training pilots until August 1945 but saw limited combat.

After Japan’s surrender, many Kaiten facilities were destroyed or abandoned. Surviving pilots (some cracked psychologically) lived with a lifetime of guilt and questions about their almost-used lives.

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9. Impact, Legacy and Historical Interpretation

Despite the ultimate sacrifice of the pilots, the operational record of the Kaiten was militarily insignificant.

• First Attack: On November 20, 1944, the first mission, involving submarines I-47 and I-36, successfully breached the heavily guarded Ulithi Atoll anchorage.

  • The single major confirmed success was the sinking of the fleet oiler USS Mississinewa, which sank after a massive secondary explosion from its cargo of aviation gasoline, killing 63 crewmen. Lieutenant (j.g.) Sekio Nishina, the co-inventor, is believed to have piloted the Kaiten that sank the ship.

• Only Other Sinking: The only other verified ship sunk by a Kaiten was the destroyer escort USS Underhill on July 24, 1945, which was blown in half by the blast, killing 113 sailors. An infantry landing craft (LCI(L)-600) was also sunk.

• High Losses: The program resulted in the deaths of:

  • 104 Kaiten pilots (in training and combat).

  • 846 Japanese submariners when eight of their carrier submarines were sunk by Allied forces, which often located them due to the difficulties and vulnerabilities of launching the Kaiten.

The Kaiten was a technically flawed and often unreliable weapon, frequently suffering from water leakage, engine malfunctions, or simply missing its target. Its true significance lies not in its military success, but in its profound reflection of the cultural and strategic desperation of Imperial Japan in the final year of the war.

Today the Kaiten are remembered as:

• One of the most extreme forms of wartime sacrifice

• A symbol of Japan’s desperation

• A tragic exploitation of young volunteers

• A reminder of the destructive force of ideological warfare

Memorials exist at:

• Ōtsushima Kaiten Museum (the main Kaiten training base)

• Graves and cenotaphs honoring the pilots

Interpretations vary:

• Some see them as brave warriors

• Others view them as victims of militaristic coercion

• Historians generally classify Kaiten as militarily ineffective but psychologically intense weapons 

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