Sealed in Steel: The Harrowing Story of the Kaiten, Japan's WWII Suicide Torpedoes

When we think of Japan's last-ditch efforts in World War II, the image of the Kamikaze pilot is indelible—a plane purposefully diving towards an enemy ship. But beneath the waves, an even more claustrophobic and terrifying weapon was deployed: the Kaiten, a manned suicide torpedo. This was not a vehicle you could bail out of; it was a coffin you steered to your death.

A Weapon Born of Desperation

By 1943, the tide of the Pacific War had turned decisively against Japan. With its naval fleet decimated after battles like Midway, the Imperial Japanese Navy sought radical solutions to counter the overwhelming industrial and military might of the Allied forces. Two young naval officers, Lieutenant Hiroshi Kuroki and Lieutenant Sekio Nishina, proposed the concept of a manned, steerable torpedo. Initially rejected due to its suicidal nature, the worsening war situation eventually led the naval high command to approve the weapon's development. They named it Kaiten, a word that ominously translates to "the heaven shaker" or "turner of the heavens."

Designing the "Heaven Shaker"

The Kaiten was essentially a modified Type 93 "Long Lance" torpedo, one of the most advanced naval torpedoes of its time. A small, cramped cockpit was inserted into the middle, large enough for one man, a simple periscope, and basic controls. In the nose sat a massive 3,420 lb (1,550 kg) warhead, more than triple the size of a standard torpedo's charge. The pilot, often a volunteer in his late teens or early twenties, would be launched from a mother submarine several miles from his target. His task was to navigate treacherous waters, avoid detection, and guide his human-guided missile directly into the hull of an enemy ship.

A One-Way Mission

The grim finality of the Kaiten mission is what sets it apart. Once the pilot entered the torpedo, the hatch was sealed from the outside. There was no way for him to open it again. Escape was not an option. This stark reality was understood by every volunteer, many of whom left behind letters and last testaments for their families.

I will be a shield for His Majesty and die. We are 100 million people with a single-minded devotion to the Emperor and the country. If all of us are ready to display our spirit of self-sacrifice, we are sure to be victorious.

This sentiment, common in the letters of special attack unit members, highlights the intense nationalistic fervor that drove these young men. The mission plan included a final, horrifying instruction: if the attack run failed or the torpedo malfunctioned, the pilot was to trigger a self-destruct mechanism. This ensured the weapon's technology would not fall into enemy hands and, more to the point, guaranteed the pilot's death. There was no coming back.

A Tragic and Ineffective Legacy

Despite the immense sacrifice of its pilots, the Kaiten program was largely a strategic failure. Training was perilous, and many pilots died in accidents. In combat, they proved to be wildly inaccurate. The high speeds and the limited view from a small periscope made targeting incredibly difficult. Over 100 Kaiten pilots perished, along with more than 800 sailors on the mother submarines that were sunk while trying to deploy them. In return, they are confirmed to have sunk only two American ships: the fleet oiler USS Mississinewa and the destroyer escort USS Underhill. The Kaiten remains a chilling testament to the extremes of wartime desperation, a story of brave young men sent to their deaths in a futile attempt to turn the heavens.

Sources

• Wikipedia: Kaiten
• U.S. Naval Institute: Japan's Suicide Submarines
• The National WWII Museum: Kaiten Human Torpedo