Of the various weapons used in war, the most sinister, at least to most Americans, is what Japan used against them in World War II. The kamikaze was a nightmare to many American servicemen and could decimate ships with just a few direct hits. This, though, was only one facet of the program of suicide missions that the Japanese used.
One of the other suicide machines used was a thing called a Kaiten. Kaiten in Japanese means turning of the Heavens and was designed to change the tide of the war. Some describe the Kaiten as a mini submarine, but the more correct way is to describe it as a guided torpedo with a seat. The Kaiten program was started in February 1944 and by November, 20 were operational. There were at least five models of Kaiten built based on the frames of at least two torpedoes. The type 1 was the only Kaiten to ever see action. Developed based on the type 93 torpedo that used compressed pure oxygen as an oxidizer instead of just air the type 1 was only a 1 seater craft. A two seat craft, the type 2, was also developed and is often confused with the Japanese mini-subs, Ko-hyoteki, but this was never meant to return. These were one fire munitions that detonated their massive war heads and killed its pilot. Early models were developed so that the pilot could escape, but it is unsure if these ever saw production.
The Kaitens were very finicky. Though based on the highly successful ‘Long Lance’ type 93 torpedo this did not translate into the Kaiten being successful. Kaitens were designed to be carried and fired from the outside of their mother submarines. This not only required that the submarine surface for the Kaiten pilot to enter the his mount but also restricted the diving ability of the sub itself. Once launched, as one of as many as six on the sub, the pilot would then run at periscope depth to attain a bearing on the target. Then the plan was to lock in the controls on the final run as it ran towards its target at just 13 feet usually about 550 yards from the target. If the torpedo missed then in theory the pilot could turn it around and have another run at the target. This only sometimes occurred. Kaitens were very difficult to control and had many technical problems associated with them. Many Kaiten pilots found themselves hopelessly lost in the middle of the ocean and self detonated other than face the consequences.
During the war only two ships were reported by the United States as sunk because of Kaiten attacks. This is in stark contrast who say that many more ships were sunk due to this activity. According to US records only the tanker Mississinewa and the destroyer the USS Underhill were sunk due to direct attacks on them by Kaiten guided torpedoes. This is in stark contrast to the at least eight Japanese submarines that were lost in action that carried Kaitens. In action the Kaitnes resulted in at least 162 American deaths while many more ships may have been damaged. This is in contrast to the 145 Kaiten pilots who lost their lives (15 died in training accidents). But in addition almost 600 Japanese sailors lost their lives due to carrying Kaitens aboard the eight submarines lost.