Did Japan Have A Submarine Aircraft Carrier?

Did Japan Have A Submarine Aircraft Carrier?

World War 2

The largest submarines of their time, and designed to carry three Aichi M6A Seiran aircraft used for bombing attacks on the United States. The Imperial Japanese Navy I-400 class submarines were behemoths of World War II.

The I-400 class submarines became developed as part of Japan’s attempt to counter the overwhelming naval power of the United States. Japan’s naval strategy during the war emphasized the use of submarines. And the I-400 class submarines became seen as a way to strike at the American mainland from the sea. The submarines were also designed to be used in conjunction with Japan’s midget submarines. Which were to infiltrate American harbors and launch surprise attacks on ships and other targets.

For futher reading see our piece: Attacks on the United States during World War II

The first I-400 class submarine, the I-400, was launched in December 1942, and was followed by the I-401 and I-402. However, due to the war situation and the shortage of resources, only 3 of these massive submarines were ever built.

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Members of the US Navy inspecting the plane hangar of I 400.

Moreover, the IJN equipped the submarines with a wide range of weapons. Including torpedoes, deck guns, and anti-aircraft guns. Also equipped with a snorkel, which allowed them to run their diesel engines while submerged, and a radar system, which was unusual for submarines at the time.

US Navy personnel inspecting the gun of I-400.
The I-400 class submarines were first used in combat in July 1945. When sailed on a mission to to attack the Panama Canal.
The Japanese submarine I-402 Japanese submarine I-402 2 at Kure, Japan

However, the attack became called off due to the atomic bombing of Hiroshima and Nagasaki. Furthermore, the subsequent surrender of Japan. Following the surrender, the I-400 class submarines were scuttled by their crews to prevent them from falling into American hands.

The Aichi M6A Seiran

In recent years, the remains of the I-400 class submarines became discovered in the Pacific Ocean, and have been studied by historians and naval experts. The I-400 class submarines represent an important chapter in the history of naval warfare, and they continue to be a subject of fascination and interest today.

Officers of I-400 in front of the plane hangar. Photographed by the US Navy following the surrender of the submarine at sea, one week after the end of hostilities.
Overall, the I-400 class submarines were a unique and ambitious project by the Imperial Japanese Navy.
Japanese Submarine I-400 with Japanese crew aboard after the Surrender in 1945
Sinking of a Japanese “I-boat” submarine, during mass scuttling of Japanese subs off Sasebo, 1 April 1946. Another submarine is awaiting sinking, as a PBM flies overhead

One that unfortunately, due to the war situation and the shortage of resources, never had the chance to prove their worth in battle.

ex-Japanse submarine aircraft-carrier I-400 in US possesion
The U.S. Navy submarine tender USS Euryale (AS-22) at Sasebo, Japan, in November 1945. She has three large Japanese submarines alongside. They are (from inboard to outboard): I-401, I-14 and I-400.
The United States Navy submarine tender USS Proteus (AS-19) (left). And Imperial Japanese Navy submarines Japanese submarine I-14 2 (center). In addition, Japanese submarine I-400 2 (right) in port in Japan after the end of World War II.

In conclusion, their advanced technology and large size made them one of the most advanced submarines of their time. And, lastly, their legacy still holds significance in the history of naval warfare.

Did Japan Have A Submarine Aircraft Carrier?