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By late 1943 the war in the Pacific was going badly for Imperial Japan. Anticipating an attack on Japan itself, the Japanese undertook preparation for a number of desperation defences. One of them was the Shinyo (“Sea Quake”) class of suicide explosive boats.
The Shinyo were small, wooden, one man boats packing a 270kg charge in the bow. This was triggered either manually, or by an impact trigger (the wooden assembly protruding from the bow is part of this trigger). They were most definitely a suicide boat.
Sources vary on the speed of the Shinyos. Most of the ones I have found state that they achieved around 30 knots, whilst one that I have generally found trustworthy states that they were limited to a more sedate 18 knots whilst filled up with explosives, but that the rockets on board allowed them to accelerate to higher speeds during the attack.
Whatever the case, these otherwise unarmed boats were made in the thousands and intended to attack American invasion forces. In practice they don’t seem to have had a huge impact, possibly because most were being held in reserve for the invasion of Japan’s main islands, which never came. They did manage to sink a number of American boats and ships, mainly in and around the Philippines and Okinawa.
IJN Shinyo Explosive Boat High Speed – the boat with its bow lifted up, as if travelling at speed.
IJN Shinyo Explosive Boat Low Speed – lying flat, as for moving at lower speeds.
IJN Shinyo Explosive Boat Full Hull – the entire boat, not waterlined.