Military History

Historical Naval Mystery Solved

  Words by Cameron Dunn.

The Japanese I-400 submarine utilized during World War II has been discovered by researchers at the University of Hawaii and the national Oceanic and Atmospheric Administration on the bottom of the Pacific Ocean 2,300 feet below the surface off the Island of Oahu after over half a century of mystery surrounding its whereabouts.  The actual discovery took place in August but the announcement was made yesterday after the findings were finally confirmed with the U.S. state department and Japanese government officials.  The sub was thought to be further out to sea which made the discovery so surprising.


This boat holds great historical significance as being one of Japans major engineering accomplishments.  Designed to launch stealth airstrikes against the U.S., the I-400 was the first of three Japanese submarines equip with airstrike capabilities.  This boat was suited with sonar-damping technology and could house three Aichi M6A Seiran aircraft to deploy against enemy targets.  It also had the ability to travel one and a half times around the globe without having to refuel and could deploy three bombers within minutes of resurfacing.  The original plan to build a total of 18 of this type of boat was never accomplished.


The I-400 submarine was captured by a U.S. Navy destroyer at the end of the war and kept along with four other Japanese submarines at Pearl Harbor with the intention of inspecting in the future.  However, as the Cold War was just beginning and tensions mounted with the Soviet Union who were demanding to have the submarines made accessible to them under terms of a World War II treaty, the U.S. Navy scuttled the submarines.  They did not want that kind of technology in the hands of the Soviets. The Navy claimed ignorance and said they did not have any idea of the whereabouts of the submarines.


With the discovery of the I-400 submarine, the Hawaii Undersea Research laboratory has now located four of the five scuttled subs. 

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