The I-400-class submarine Imperial Japanese Navy (IJN) submarines were the largest submarines of World War II and remained the largest ever built until the construction of nuclear ballistic missile submarines in the 1960s. They were submarine aircraft carriers able to carry three Aichi M6A Seiran aircraft underwater to their destinations. They were designed to surface, launch their planes, then quickly dive again before they were discovered. They also carried torpedoes for close-range combat.
The I-400 class was designed with the range to travel anywhere in the world and return. A fleet of 18 boats was planned in 1942, and work started on the first in January 1943 at the Kure, Hiroshima arsenal. Within a year the plan was scaled back to five, of which only three (I-400 at Kure, and I-401 and I-402 at Sasebo) were completed. None were used operationally. I-400 and I-401 were evaluated by the US Navy in Hawaii and then sunk in deep water.
Photographs of scale models of the I-400 can be found here.
I-400 Class Photographs
Officers of submarine I-400, circa late Aug 1945 ww2dbaseJapanese Crew on deck ready to leave the Japanese Submarine I-400I-400 with Japanese crew aboard after the Surrender in 1945I-400 Men pass cargo down the lineJapanese crew mustered on deck after surrender. Note US sailors with gunsOutermost sub, is the I-14 She carried two aircraft the two inner side boats are I-400 ClassUSS Euryale (AS-22)Sasebo, Japan, in November 1945. She has three large Japanese submarines alongside. They are (from inboard to outboard) I-401, I-14 and I-400Two I-400-class submarines and I-14 (right)I-401 and I-14 alongside of USS Proteus (far left), Yokosuka, Japan, 29 Aug 1945I-400 and another aircraft carrying submarine, alongside the USS Proteus at YokosukaI-401 alongside of USS Proteus, Yokosuka, Japan, 29 Aug 1945I-400 Class SubmarineI-401I-401 I 400 at Pearl Harbor2 captured I-400 class submarines and I-14 in Tokyo Bay, 1945I-400 Class Submarine with numerous other subs and shipsAt right are the ex-Japanese submarines I-14, I-401, and I-400Ex-Japanese subs I-14, I-401, and I-400 are in lower left. At right centre is USS Bowditch 27 February 1946I-400 class submarine sinking after being used as target
External Detail
I-400 Class after 5.5″ deck gunI-400 Class 25mm Guns on Deck
Hanger Detail
I-400, or I-401 Interior of the aircraft hangar, showing tracks for rolling planes outI-400 Inside of HangarHangar Watertight Door I-400 Class Submarine
Internal Detail
Main Control Room on the I-400Main Control Room on the I-400Main Control Room on the I-400I-400 inside Manoeuvring RoomI-400 Main Starboard EnginesPort Engine room I-400I-400 Man stands with Radar GearOfficer’s Quarters Amidship Port I-400I-400 Class Forward Upper Torpedo RoomI-400 Class Crew’s Living Quarters aft
