Many submarines were modified to carry and launch three to six kaitens. The pilots entered the weapons while submerged through a connecting hatch. The ideal scenario would be for the mother sub to launch the weapons 7-8,000 meters from target. He would be on compass heading only and would risk use of the periscope only to acquire the target about 1-1,500 meters out.

The few successful contacts resulted in thunderous destruction but the vast majority of missions led to nothing at all. Kaitens must have missed entirely and ran out of power or were sunk by either enemy or mechanical failures. At any rate the successes did not justify the expenditure of lives.

Regarding the Kaiten carried by I-58 during the patrol, which resulted in the loss of the USS Indianapolis, the following details emerge. I-58 departed Kure on July 16, 1945 and immediately returned to repair Kaiten periscopes. On July 18, Hashimoto once again departed for his station east of the Philippines.

At 1400 hours, on July 28, I-58 sighted what Hashimoto identified as a tanker and destroyer escort. He launched two Kaiten at this time and claimed two hits. In fact, the cargo ship Wild Hunter, and destroyer Lowry were the targets. Lowry sustained moderate damage from an explosion; the submarine was reported to authorities. Apparently, USS Indianapolis was not informed of this incident (she had departed Guam several hours prior to the attack) although Captain McVay was informed of IJN submarine activity in the area east of the Philippines. After the sinking of USS Indianapolis, Hashimoto proceeded to patrol for targets between Okinawa and Leyte. On the morning of August 10 Hashimoto launched a Kaiten against destroyer escort Johnnie Hutchins and a second against four of her sisters. He escaped upon the surface and claimed to have sunk two destroyers.

In what would prove to be Hashimoto’s last Kaiten launch during the war the USS Oak Hill — a landing ship, dock — and destroyer escort Thomas F. Nickel were sighted late in the afternoon of August 12, some 350 miles southeast of Okinawa. Identifying the vessels as a seaplane carrier and destroyer escort, Hashimoto launched his last operational Kaiten. At about 1830 hours Oak Hill sighted a periscope close aboard and maneuvered to evade. Nickel charged in to attack, heard the Kaiten scrape along her port side and watched the craft explode some 2,500 yards away. Hashimoto recorded the explosion and subsequent depth charging which the Nickel had commenced when Oak Hill reported a second periscope in the vicinity. Recording an apparent hit, Hashimoto returned to Japan immediately thereafter.”

My source is “Suicide Squads,” by Richard O’Neill (published in 1981).

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Movie Deguchi no Nai Umi

Used by the IJN in the final stages of WWII, the Kaiten Type 1 was a Type 93 torpedo modified as a one-man suicide weapon, although provisions were made for the pilot to escape before impact. In practice, however, none attempted to escape. With over 400 Kaitens built, only 100 were ever sent on missions, and out of those 100 missions only two succeeded in sinking enemy ships. In the end, the unmodified, unmanned Type 93 torpedo used conventionally was a much more effective weapon.