I-400 class
I-401 on September 15, 1945
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The I-400 - or Sen-Toku class ( Jap. 伊四〇〇型潜水艦 , I-yonhyaku-gata sensuikan , German Submarine I-400 ) was a class of U-cruisers of the Imperial Japanese Navy from the Second World War . The boats in the class were the largest conventionally propelled submarines ever built. In addition to the AM class , the Sen Toku class was the only one that could bring multiple dive combat aircraft into service.
history
planning
Submarines as underwater aircraft carriers that could carry aircraft have been built in Japan since 1937. In order to be able to attack the American mainland effectively, the Japanese Admiralty decided in 1942 to build a fleet of large underwater aircraft mother ships. The specification included the ability to transport three aircraft with the appropriate bomb equipment and the most necessary spare parts (or another dismantled aircraft) and a range of 70,000 km. This meant that operations anywhere in the world would have been possible from Japan. Bomb attacks were planned on the coastal cities of the United States (including New York City and Washington, DC ) and on the locks of the Panama Canal . The destruction of these locks would have caused the Gatunsee to leak at least in part and thus interrupt the American connection between the Atlantic and Pacific for months, which would have given the Japanese a significant strategic advantage. The first planning was based on 18 units to be built. The first boat in this series was named I-400 and thus established the class named after him.
Conception
The 100 m long pressure hull consisted of two 2/3 pipes which were welded together and which tapered towards the ends into one-piece conical stumps. The bulkheads were sealed off with round passages. The superstructures were then arranged around the pressure hull , the hull , the hangar and the tower , all of which were somewhat asymmetrical. With this design enough space was available without making the boat too long and too deep, which would have adversely affected maneuverability. In the bow there were two torpedo rooms, one above the other, each with four torpedo discharge tubes and ten torpedoes , in the stern two engine rooms with two diesel and one electric motors each for driving the propellers. In the middle of the fuselage were the command center , the galley , a room with auxiliary equipment and a workshop for the maintenance of the aircraft engines, behind which the crew quarters. The food supplies should allow four-month missions.
The tower was connected to the pressure hull with a 7.6 m deep shaft. In the event of a diving alarm, the lookout team then had to vacate the tower and close the hatch within 56 seconds . A 90 cm thick pillow was laid out in the control room under the shaft to intercept the falling sailors . A 25 mm anti-aircraft gun was installed on the tower . In addition, there were the usual optical equipment ( periscopes made in Germany) and a snorkel for permanent diving. The radar equipment was state-of-the-art from the Japanese Navy and consisted of the submarine version of the air search radar type 13 with a reduced antenna, the sea search radar type 22 with a common transmitter and receiver horn and the passive system E-27 including direction finder.
The hangar was an autonomous cylindrical pressure hull built on the deck , 35 m long, 3.6 m diameter. Four air torpedoes and 15 bombs could be carried. Three anti-aircraft triplets caliber 25 mm were attached to the hangar. In front of the hangar was a catapult operated with compressed air for starting the aircraft and an erectable crane . On the quarterdeck behind the hangar was a 140mm cannon . The superstructure and parts of the fuselage were covered with an elastic rubber layer, which was apparently intended to dampen the reflections of noises.
The main armament was three Aichi M6A1 Seiran bombers with removable wings that could carry up to 900 kg bombs or an 800 kg air torpedo caliber 450 mm and land on the water after the mission was over. All three aircraft could be assembled, refueled, ammunitioned, and airborne within 45 minutes of surfacing.
The nominal crew was 144 to 157 men, but it could be more than 200 during operations. Since there were not enough berths , many sailors slept on mats where there was space. The sanitary facilities were extremely simple.
A maximum speed of 24 knots was achieved during test drives . The behavior of the boats that appeared in the storm was expressly praised.
construction
A total of five boats were laid on the keel. I-400 and I-404 on the Kure Kaigun Kosho ( Kure Naval Shipyard ), I-401 and I-402 on the Sasebo Kaigun Kosho ( Sasebo Naval Shipyard ) and I-405 in Kobe at the Mitsubishi Shipyard . The construction work was delayed by attacks by American planes, in which the boats were damaged several times. In the end, only I-400 , I-401 and I-402 were put into service , which was last converted to a tanker , but was no longer used.
On December 30, 1944, I-400 was assigned to the first submarine division of the 6th Fleet, consisting of I-401 and the smaller submarines I-13 and I-14 (KAI-Ko-Gata class) that could each carry two planes. The squadron then began combat exercises west of the Japanese islands.
Fuel was needed to continue, but was in short supply in Japan in early 1945. That is why the first long voyage from I-400 led to the Japanese naval base in Dalian in China ( Port Arthur ) in mid-April 1945 to stash fuel for further operations.
assignment
By the early summer of 1945 the war was so advanced that the Panama Plan was abandoned. On June 12, 1945, the Admiralty decided to attack the large American base on the Ulithi Atoll with the existing squadron .
The corresponding plan ARASHI (mountain storm ) was drawn up on June 25, 1945 (four days after the fall of Okinawa ): According to it, I-13 and I-14 were supposed to transport four dismantled long-range reconnaissance aircraft of the type Nakajima C6N1 Saiun to Truk, where they were should be mounted. Launched from Truk, these machines were supposed to explore the main targets ( aircraft carriers , meeting places) and transmit the information to I-400 and I-401 , which would then attack with their six Seiran. The attack should take place on the night of the full moon on August 17th (or later, until August 25th) and the squadron should then go to Singapore for new supplies . All boats would take a route via Hong Kong , where I-13 and I-14 would take their four Seirans, and there were six reserve machines for I-400 and I-401 , as kamikaze suicide attacks were primarily planned with the loss of the original aircraft . In mid-July 1945, the boats received the necessary equipment, provisions for three months, the aircraft received American emblems and the aircraft crews received the gifts of honor customary for kamikaze pilots.
On July 23, 1945 ran I-400 and I-401 from Ominato from. They were supposed to establish radio communication with each other on August 14th and meet on August 16th at the island of Pohnpei ( Karolinen ). However, the radio transmission of the meeting point coordinates went wrong and the contact was not established, so that the date of the attack passed. It was not until August 18 that the boats received the news that Japan had surrendered on August 15 and the order to break off the operation and return to Kure.
Surrender and surrender
On August 26, 1945, the boats were ordered to fly black flags of surrender. All aircraft, ammunition and other weapons and important documents were thrown overboard. The next day, I-400 was taken over by a 44-man American prize squad on the open sea off Tokyo . The same fate befell the other three boats. On I-401 , the squadron's commander, Captain Ariizumi, shot himself in his cabin. The official handover to the US Navy took place on September 2, and it was removed from the Japanese warship register on September 15 . At the end of September, the boats were transferred to Sasebo by American crews . From there, on December 11, 1945, they started the journey to Pearl Harbor . I-401 and I-14 were under the command of sons of merited American admirals.
After stops on Guam , Eniwetok- Atoll and Kwajalein- Atoll, the boats arrived in Pearl Harbor on January 6, 1946. In February the boats were drained and examined. In March it was decided in Washington to sink the boats; they did not want to have them examined by the Soviet Union , which was formally still allied. The boats were used as targets for novel electric torpedoes. I-402 was sunk on April 1, 1946 in the Goto Islands , I-401 and I-400 on May 31 and June 4 in Hawaii . I-405 and the 95% finished I-404 were scrapped.
Only on November 10, 1959, the USS Triton was a larger submarine put into service by the US Navy. Even the George Washington class , which was commissioned from December 30, 1959 and equipped with 16 ballistic missiles , had a lower underwater displacement.
On March 17, 2005, the wreck of I-401 was found near Hawaii. I-14 was found in 2009 by a search expedition from the Hawaii Undersea Research Laboratory and the National Oceanic and Atmospheric Administration .
The wreck of the Class I-400 boat was found accidentally off the island of Oahu in August 2013 by an expedition of marine researchers from the Daily Mail while searching for other sunken ships. Also close to the coast of Hawaii like its sister ship I-401 .
Literature (selection)
- Henry Sakaida, Gary Nila, Koji Takaki: I-400 - Japan's Secret Aircraft Carrying Strike Submarine. Hikoki, Crowborough 2006, ISBN 1-902109-45-7 .
- Maru Special: Japanese Naval Vessels. Vol. 13: Submarines Type Sen-Toko (I-400 Class and I-13 Class). Tokyo 1977.
- Maruzen (Ed.): The Imperial Japanese Navy. Vol. 12: Submarines. 2nd Edition. Tokyo 1995, ISBN 4-7698-0462-8 .
- Tadeusz Januszewski: Japanese Submarine Aircraft. Mushroom Publications, Redbourn 2002, ISBN 83-916327-2-5 .
Web links
- Sen Toku Type . combinedfleet.com (English) Description and specification with pictures and further links
- The Pacific travel of I-400 (English)
- mediencenter.n24.de Documentation about searching and finding the I-401 near Oahu (search term "Japan")
- Arno Frank: Japan's aircraft carrier submarines. Downfall of the deadly giants. one day (articles and historical photos), published and accessed January 3, 2013
- With these underwater carriers, Japan wanted to attack the United States
Individual evidence
- ↑ see sketch
- ↑ USTMJ S-01-7. Characteristics of Japanese Naval Vessels , Article 7, Submarines, Supplement II, p. 40
- ^ 2 Sunken Japanese Subs Are Found Off Hawaii . New York Times
- ^ N24 news
