Japan confronted the American fleet with human torpedoes in 1943

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During the final years of World War II, Germany devoted significant resources to developing what was known as the "Wunderwaffe", hoping to change the course of the war. These projects included jet aircraft and ballistic missiles, as well as designs for giant weapons, such as the Ratte tank, which was scheduled to weigh a thousand tons, but was not built.

Through these projects, the German leadership sought to enhance its military capabilities and raise the morale of the army and the people, as the Allies continued to advance.

On the other hand, Japan, at the end of the war, turned to developing suicide weapons, depleting part of its human and material resources. These programs were not limited to aircraft, but extended to boats and torpedoes piloted by humans, all the way to preparing divers to carry out underwater attacks.

The most prominent of these weapons is the Kaiten torpedo, which was designed to be led by a person towards an enemy ship, in an attack that ends with the death of its commander. According to the US Navy Historical Center, the idea of ​​human torpedoes was proposed in 1943 and received approval early the following year, before being turned into a suicide weapon as the Japanese military situation worsened.

The idea of ​​using human beings in attacks where they could not survive was initially met with objections within the Japanese Navy. But a succession of defeats and the increasing risk of the war reaching Japanese territory prompted the leadership to adopt these weapons, hoping to turn the tide of fighting.

The special attack programs included planes and boats loaded with explosives, the pilot of which directed them towards enemy ships and rammed them, trying to bypass defensive fire.

Among these weapons were the Ohka plane, equipped with about 1,200 kilograms of explosives, and the Shinyo boats, which carried more than 200 kilograms of high explosive materials.

The program also extended to developing human-driven torpedoes towards their targets, and preparing divers carrying explosive charges to attack enemy naval vessels.

Work on the Kaiten idea began in 1943, and the weapon entered service the following year. Its first version was based on the Japanese Type 93 torpedo, after it was modified by adding a commander's cabin, control tools, and a short periscope to follow the target.

The first version was about 14.75 meters long, weighed more than eight tons, and carried a warhead containing about 1.5 tons of explosives. Its maximum speed reached about 30 knots.

The torpedo pilot controlled its direction, speed, and depth, and used periscopes to correct its course toward the target ship. Japan equipped submarines and some ships to carry and launch these torpedoes.

Despite the production of hundreds of torpedoes, their combat successes remained limited. One of the most prominent documented attacks is the sinking of the American fuel tanker USS Mississinewa in Ulithi on November 20, 1944.

According to the US Naval History and Heritage Command, about 330 torpedoes of the first version were produced, and about 100 of them were used, with limited results compared to what Japanese reports and propaganda promoted at the time.

In preparation for defending the Japanese islands against a possible Allied landing, the Fukuryu program emerged, which relied on divers equipped with special suits and underwater breathing apparatus.

Their equipment included two oxygen cylinders, an air purification system, and the possibility of taking liquid food. The plans aimed to enable them to remain under water for long hours, perhaps up to ten hours.

The diver carried a mine attached to the end of a long stick, to be used to attack the bottom or side of the landing craft. The mine explosion would have killed the diver, in addition to causing damage to the target.

According to a study published by the US Naval Institute, the number of trainees in one of the program units reached about 1,200 people by the end of the war. But equipment shortages and production difficulties hampered preparations, and the effectiveness of the "Fukuryu" was not tested in actual combat before Japan's surrender.