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| IJN I-400-class submarine Sentoku Type 5,223 Tons (surfaced) 6,560 Tons (submerged) 122m x 12m x 7m 8 x torpedo tubes 14cm/40 deck gun 3 x 3x25mm AA guns 3 x M6A1 Seiran  USN 1945    HURL March 17, 2005 |
Sub History Built by Sasebo Naval Arsenal at Sasebo. Laid down April 26, 1943 as as I-400-class submarine Sentoku Type. The submarine included radar, radar detectors and watertight hangar for three Aichi M6A1 Serian seaplanes. Launched March 11, 1944 as I-401 with LtCdr Nobukiyo Nambu as Chief Equipping Officer (CEO). On December 15, 1944 the 631 Kokutai (631 Air Group) is formed for a special attack mission by ten submarine launched Aichi M6A1 Serians that would attack the Panama Canal. Completed and commissioned January 8, 1945 in the Imperial Japanese Navy (IJN) under the command of Captain Tatsunosuke Ariizumi with Commanding Officer (C.O.) LtCdr Nobukiyo Nambu. Registered in the Kure Naval District. Assigned to the Sixth Fleet, SubDiv 1 as the flagship with I-13, I-14 and I-400. Wartime History The Japanese Navy planned to use the I-400 along with the I-401, I-13 and I-14 to participate in a daring plan to attack the Panama Canal and disable its locks. During June 1945 the decision was made to switch targets to hit USN anchorage at Ulithi Atoll. The operation was code named Arashi (storm) for the I-400 and I-401 to use their Serians painted in U.S. markings and armed with bombs for a kamikaze attack against any aircraft carriers at Ulithi Atoll. On July 23, 1945 at 4:00pm departs Ominato following I-400 the left two hours earlier. At 8:15pm while negotiating Tsugaru Strait, mistaken for an Allied submarine and fired on by Japanese 150mm guns on Shiokubi Cape on Hokkaido but escapes without damage. The two submarines proceed on separate tracks to the east and plant to rendezvous on August 16, 1945. On July 24, 1945 at 6:30am exits Tsugaru Strait and surfaces. On July 28, 1945 enters heavy storms and typhoon conditions at sea. During the storm, spots an unescorted U.S. tanker but deos not attack to endanger the operation. On July 31, 1945 off Marcus Island, surfaced and speeds to 19 knots to make up lost time due to the weather. On August 14, 1945, observes U.S. aircraft and screw noise near Marcus Island and sends a coded message to I-400 to change to a new rendezvous point 100 miles south of Ponape, but I-400 fails to receive the message. When I-401 surfaces at the new point and unable to find the other submarine, it departs for the next rendezvous point scheduled for August 17, 1945 south of Ulithi Atoll. On August 15, 1945 the submarine learns that Japan has surrendered but the senior leadership decide to ignore the news believing it lacks credibility. On August 18, 1945 the operation Arashi is canceled by Vice Admiral Daigo and I-400 and I-401 are ordered to Kure. Aboard I-401, the crew want to proceed to Truk and keep fighting while ComSubDiv 1 suggests returning to either Ominato or Nanao to be scuttled off Japan. On August 26, 1945 the submarine is ordered to host a black surrender flag and surfaces. The three Aichi M6A1 Serian are assembled without ordnance run up and catapulted unmanned into the sea. The derrick drops all aerial bombs overboard and all twenty of the submarine's Type 95 torpedoes are fired. Aboard, code books, logs, charts and documents are destroyed. On August 29, 1945 around midngight off Sanriku Bight east of Honshu spots a vessel and avoids at full speed. At dawn, the port engine fails and is spotted on radar by USS Segundo (SS-398) and using international signals orders her to halt. Aboard I-401, Navigation Officer, Lt Bando Muneo was sent aboad the submarine and after he returns, Cdr Nambu contacts Tokyo for instructions and is ordered to surrender and a prize crew led by Lt J. E. Balson plus five sailors boards. They are given a bottle of Suntory whiskey but do not go below deck and her deck hatches are secured with chains open to prevent the submarine from diving and believe the Americans want them to proceed to Yokosuka while ComSubDiv 1 orders them to Ominato and Captain Ariizumi suggested they should scuttle the submarine. Now in command, Lt Balson orders I-401 to Tokyo. On August 30, 1945 in the early morning, off Izu Oshima Captain Ariizumi commits suicide with his pistol in his cabin. His body is wrapped in a Japanese flag and release overboard without the Americans observing. On August 31, 1945 at 5:00am enter Sagami Bay with USS Segundo (SS-398) and the U.S. flag is raised while LtCdr Nambu surrenders two sword to Lt Balson and the prize crew. Later that day, Cdr Arthur C. Smith and a prize crew arrive from USS Proteus (AS-19) to relieve the initial prize crew and proceeds to Yokosuka where it is moored with I-400 and I-14. On September 1, 1945 the Japanese Navy flag is lowered ahead of the official surrender. On September 15, 1945 officially removed from the Navy list. On September 29, 1945 inspected by Vice Admiral John H. Towers, Commander of Task Force 38 (TF 38). On October 29, 1945 under the command of Cdr Edward D. Spruance and a crew of forty Americans departs Yokosuka for Sasebo with I-400 and I-14 escorted by USS Greenlet (ASR-10). Afterwards, steamed across the Pacific to Hawaii. On January 6, 1946 arrives at Pearl Harbor at the submarine base and welcomed by a Navy band and celebrities. Sinking History On May 31, 1946 at 10:59am off Barber's Point on Oahu sunk by two torpedoes fired by USS Cabezon (SS-334), to test the Mark 10-3 exploder in deep water. Over the course of several days four captured subs were sunk including I-201, I-14, and I-400. Shipwreck On March 17, 2005, University of Hawaii's Hawaii Undersea Research Laboratory's (HURL) Pisces submersible discovered the submarine lying flat on the sea floor at 2,665' / 820m. It was identified from the "I-401" painted in white on the left side of the coning tower. Pisces recorded video and photographs of the wreckage. Artifacts Prior to the sinking, some items were taken by U.S. Navy personnel and later sold or traded to collectors. The Yokohama WWII Japanese Military Radio Museum has two items from the I-401 on display: gun sight and M6A1 Serian bomb site. References Combined Fleet - IJN Submarine I-401: Tabular Record of Movement Air & Space Magazine "All and Nothing" November 2001 Issue, pages 22 - 31 HURL: I-401 Found off Barber's Point I-400: Japan's Secret Aircraft-Carrying Strike Submarine: Objective Panama Canal by Henry Sakaida, Gary Nila and Koji Takaki National Geographic "Hunt for Samurai Subs" November 17, 2009 Contribute
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