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Sunken Japanese Supersub From World War II Located Off Hawaii

An aircraft-carrying Japanese supersubmarine built during World War II has been found on the bottom of the Pacific Ocean off Oahu, nearly 60 years after it was hastily scuttled by the U.S. Navy in an effort to keep its technology out of Soviet hands.

Reuters reports:

"The accidental discovery of the 1-400 ... on the rock- and debris-littered ocean floor, some 2,300 feet beneath the surface, has solved the mystery surrounding a ship long thought to be further afield.

" 'We came upon this as we were looking for other targets ... It is like watching a shark at rest,' said Jim Delgado, a researcher aboard the Pisces V deep-diving submersible which traveled to the wreckage."

The I-400, the first of three giant Japanese boats, was designed to launch stealthy airstrikes against American cities. Originally, 18 of them were planned, but only three were actually built. The prototype of the Sen-Toku class was captured by a U.S. Navy destroyer in the closing days of the war.

As part of a treaty with the Soviet Union, Moscow wanted to have a look at the boat — at 400 feet in length, the largest submarine built at the time. It sported sonar-damping technology and carried a watertight hangar on deck capable of housing three Aichi M6A Seiran aircraft, as well as other innovations that the U.S. was worried might find their way into Soviet boats.

The Telegraph says:

"The vast submarine was a legendary feat of Japan's wartime engineering prowess, capable of circumnavigating the globe one-and-a-half times without refueling and launching three folding-wing bombers within minutes of resurfacing."

After the sub was intentionally torpedoed in 1946, the U.S. claimed to have no information on its exact location, amid Soviet protests.

The I-400 was found in August, but the announcement was just made on Tuesday. A sister ship, the I-401, was located, also off Oahu, in 2005.

Copyright 2021 NPR. To see more, visit

Scott Neuman is a reporter and editor, working mainly on breaking news for NPR's digital and radio platforms.
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