Data map: On August 22, 1945, Japanese aircraft carrier submarines received orders to destroy all weapons and surrender to the US military.

During World War II, Japan built a huge steel monster in the sea: it could cruise and attack in the deep sea, and it could also launch bombers to drop bombs in the air to destroy. Germany's "Der Spiegel" magazine recently disclosed this aircraft carrier submarine called the I-400 class.

On March 17, 2005, oceanographer Terry Kobe and his team tested a submarine in the waters near Hawaii. Suddenly, a huge monster appeared in front of us. At first, we thought it was a weird rock. But it was too big. What Kobe saw was the secret weapon aircraft carrier submarine developed by Japan.

The idea of developing this weapon came from Japanese naval commander Isoroku Yamamoto. In 1942, the Japanese army invaded China and Southeast Asian countries and regions. In addition to controlling the Asian backyard, Yamamoto's mission was to find ways to deal a devastating blow to the United States. Before that, the Japanese army had taken the first step and attacked Pearl Harbor. Yamamoto believed that if the United States continued to develop economically, Japan would lose the war in the medium term, so the war should be brought to the United States. Not long before that, Japanese submarines bombarded oil fields in California and a fort in Oregon. Although these military actions were insignificant, they greatly boosted the morale of the Japanese army. Yamamoto even planned to use submarines + aircraft to strike the heartland of the United States. Therefore, the Japanese Navy's shipbuilding plan added a total of 18 I-400-class aircraft carrier submarines. These aircraft carrier submarines can refuel more than once around the earth.

When building the I-400-class aircraft carrier submarine, the Japanese Navy encountered many problems. The first was how to launch the dive bomber type Seiran. Seiran is a model specially developed by the Japanese army for use on submarines, which can carry 800 kg of bombs or 17.71-inch diameter air-dropped torpedoes. To this end, the Japanese army built a hangar on the main deck that could accommodate three Seirans. There is also a catapult cable extending from the hangar mouth. During combat, the aircraft are dragged to the catapult in turn to unfold their wings, refuel and load ammunition, and then ejected. After completing the mission, they land on the water near the mother ship and are lifted back by a crane. Japan's catapult technology was assisted by Germany, and the periscope, special plastic coating, sonar and other technologies on the submarine also came from Germany.

The defect of this submarine is that the hangar is so heavy that the submarine is in danger of capsizing. Therefore, the designer adopted a transverse double-barrel structure. The crew compartment at the stern of the boat is restored to a single barrel, and there are two torpedo compartments at the bow. The submarine can accommodate 140 crew members and pilots. This aircraft carrier submarine is 293 feet long, with a displacement of 3,500 tons above water and 6,500 tons underwater. It is the largest submarine during World War II. Only the Benjamin Franklin-class nuclear submarine in 1959 reached a similar scale again.

The aircraft carrier submarine project was highly valued by the Japanese army. On January 13, 1942, Yamamoto decided to embark on this monster project. On April 18 of the same year, it had become a priority project for the Japanese Navy. It was also on this day that the US Air Force crossed the vast Pacific Ocean and directly bombed Tokyo. In January of the following year, the Japanese army officially started building aircraft carriers and submarines. The first operational plan formulated by Japan was to use aircraft carriers and submarines and bombings to carry out biological and chemical attacks on cities on the west coast of the United States. Considering the adverse effects of using biological and chemical weapons, Japan later changed the plan to bomb cities such as San Francisco, Washington or New York. As the United States' advantage became more and more obvious, Japan changed its plan again and aimed at the Panama Canal so that the US Navy would not be able to transport troops through the canal for several months. The Japanese army also learned from a Japanese engineer who participated in the design of the Panama Canal that year, and specially made a model of the Gatun Lock in Wugang to practice attack routines.

However, due to the frequent bombing of Wugang by US aircraft, the Japanese army's plan was disrupted. On the sea route to Panama, the US military also deployed heavy troops. The United States also took the initiative to mobilize more than 3,000 ships to prepare for an attack on the Japanese mainland. In view of the extreme lack of diesel fuel in the Japanese army, the Japanese military later ordered to cancel the bombing of the Panama Canal and instead attack the Ulithi Atoll, the U.S. military's forward base in the Western Pacific. In fact, the four aircraft carrier submarines that were commissioned in 1945 were no longer able to reverse the situation and could only watch in despair as the Americans continued to advance and dropped nuclear bombs on Hiroshima and Nagasaki. Moreover, in June of that year, the U.S. military had occupied Okinawa, and 14 aircraft carriers gathered at Ulithi Atoll, preparing to fight the Japanese army.

A week after Japan's unconditional surrender, the Japanese aircraft carrier submarines received the final order: destroy all weapons and important documents of the submarine formation. As a result, I-401 destroyed all charts, code groups, logs and important documents, and fired all torpedoes. I-400 also did a similar job. I-401 was then taken to Hawaii by the U.S. military. There, U.S. Navy experts conducted an inspection and were surprised by the advanced technology of the Japanese army. In order to prevent the Soviet Union and other communist countries from obtaining these secrets, the U.S. military destroyed these aircraft carrier submarines and sank them to the bottom of the sea in May 1946. (Aoki)

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