Japanese submarine images
The I-400 subs were the largest ever built until the Ethan Allen-class of nuclear subs in 1961. The I-400 subs not only could travel one and a half times around the world without refueling, they carried three Aichi M6A1 attack planes, which they launched off their bow when surfaced, effectively making them underwater aircraft carriers.
This is the only known photograph of a Sen-toku sub taken by the Japanese during World War II. It shows two Aichi M6A1 attack planes on deck waiting to be launched. Nicknamed Seiran, the aircraft were intended to appear over New York City and Washington, DC just as their name suggested: "like a storm from a clear sky." Only two classes of subs were purpose built to carry Seiran: the I-400 class, and the Type A modified subs (I-13 and I-14), which were based on the I-9. The I-400s carried three planes each while the I-13 and I-14 could only fit two in part because they were 28 feet shorter than the I-400's total length of 401 feet.
These five diagrams show the I-400 subs' remarkable design configuration. The largest subs in the world at the time each underwater aircraft carrier could travel one a half times around the world without refueling.
The I-14 (pictured here) and I-13 were members of Japan's Sen-toku squadron along with the I-400 and I-401. The I-14 was 370 long (60 feet longer than the USS Segundo), which was still 30 feet less than the I-400 class. As a result, she carried only two Aichi M6A1 attack planes in her water-tight deck hangar.
August 28, 1945: I-14 crewmen being off loaded as a security precaution to ensure a last minute rebellion does not break out aboard the sub.
Forty I-14 crewmen were held prisoner aboard the USS Bangust (DE-739) as American captors looked on.
Handwritten notes taken by U.S. Prize Crew member, Paul W. Wittmer, while he learned how to operate the I-401 from the sub's chief petty officers.
Logo made by the I-401's U.S. Prize crew commemorating their trip aboard the sub from Tokyo to Pearl Harbor.
November 1945: The I-400, I-401, and I-14 tied up to the USS Euryale (AS-22) in Sasebo, Japan just prior to their transit to Pearl Harbor.
The I-400, I-401, and I-14 are shown tied up to a pier at Pearl Harbor.
The U.S. Navy's unilateral decision to keep the I-400 subs out of Russian hands drew a strong protest from the Soviet Union as shown in this June 3, 1946 article from the New York Times.
The I-400 was put into dry dock at Pearl Harbor in February 1946, so U.S. Naval intelligence could conduct a thorough investigation of their technology. When the Russians asked to examine the subs, the U.S. Navy sailed them off the coast of Oahu where they were torpedoed and sunk. The Russians filed a protest but it was too late. The Cold War was already underway.
The bridge of the I-401 as she appears today at the bottom of the Pacific Ocean.