Japanese submarine I-401

The Sen Toku-class I-401 (伊号第四〇一潜水艦) was once the largest submarine in the world. It was commanded by Lieutenant Commander Nobukiyo Nambu of the Imperial Japanese Navy during World War II. Capable of carrying three two-seat Aichi M6A1 "Seiran" (Mountain Haze) float torpedo bombers, the Sen Tokus were built to launch a surprise air strike against the Panama Canal.

Service history
When the I-401 was completed and commissioned on 8 January 1945 in the Kure Naval District, the Second World War was almost over. This left the fate of I-401 uncertain. After several attempts to launch, the I-401 set course for its first target, but was stopped by Emperor Hirohito's broadcast, calling for an end to all hostilities on 15 August 1945.

On 26 August 1945, the I-401 hoisted a black flag of surrender. Its unmanned planes were catapulted into the sea, all 20 Type 95 torpedoes were destroyed, and all codes, logs, charts and secret documents were also destroyed.

Three days later, on 29 August 1945, the I-401 was picked up on USS Segundo (SS-398)'s radar. I-401 surrendered to the American ship. Lieutenant Commander Nobukiyo Nambu delivered two samurai swords, as a symbol of surrender, to Lieutenant J.E. Balson, the Segundo's Prize Crew officer.

The I-401 was finally sunk, when used as a target ship, off Pearl Harbor on 31 May 1946.

Rediscovery
On March 17 2005, the Hawaii Undersea Research Laboratory's (HURL) deep-diving submersibles Pisces IV & Pisces V located the I-401 off the coast of Kalaeloa. The I-401 lies about 820 meters (2665 feet) off the coast of Barbers Point. The bow is broken off just forward of the aircraft hangar. The two pieces are not far apart and are connected by a debris field. The main hull is sitting upright on the bottom, the numbers "I-401" are clearly visible on the sides of the conning tower. Her 25 mm antiaircraft guns seem in almost perfect condition.