Japanese submarine I-351

Upon commissioning, I-351 was assigned to Submarine Squadron 11 for workups.[1] Between late January and early April 1945, she conducted workups in the Iyo-nada in the Seto Inland Sea.[1] Originally equipped with a Type 22 surface search radar and an E27 Type 3 radar detector, she also had a Type 13 air search radar installed after testing.[1] She was assigned to Submarine Division 15 in the 6th Fleet on 4 April 1945, and continued training in the Seto Inland Sea until mid-April.[1]

On 1 May 1945, I-351 departed Kure bound for Singapore on her first transport mission, carrying a cargo of aircraft parts, ammunition, and clothing.[1] She arrived at Singapore on 15 May 1945.[1]

On 18 May 1945, Fleet Radio Unit, Melbourne (FRUMEL), an Allied signals intelligence unit in Melbourne, Australia, reported that it had decrypted a message reporting I-351′s arrival at Singapore, that she had entered drydock on 17 May 1945, and that she planned to change ballast, leave drydock on 20 May, load a cargo of aviation gasoline, and depart Singapore on 21 May.[1] She actually departed Singapore on 20 May, carrying 132,000 US gallons (500,000 L; 110,000 imp gal) of aviation gasoline.[1] FRUMEL reported on 31 May that she planned to be at position 31°00′N 126°00′E on 2 June and arrive at Sasebo, Japan, on 3 June 1945.[1] Despite this Allied awareness of her activities, she arrived safely at Sasebo on 3 June.[1] Most of the aviation gasoline she delivered was used for kamikaze operations, and 6th Fleet commander Vice Admiral Tadashige Daigo received a special commendation for her successful mission from the Commander-in-Chief of the Combined Fleet, Vice Admiral Jisaburo Ozawa.[1]

While I-351 was at Sasebo, FRUMEL reported on 14 June 1945 that she was scheduled to depart on or about 19 June for another voyage to Singapore, carrying a cargo of ammunition and cryptographic publications.[1] She actually got underway for Singapore at 14:00 on 22 June, carrying 60 boxes of code books for the 10th Area Fleet and personnel slated to command the submarines I-501 and I-502.[1] Allied Ultra intelligence accurately reported her departure that day, adding that she might be off the coast of China at 28 degrees 20 minutes North at 12:00 on 25 June 1945.[1] At 17:45 on 26 June, the United States Navy submarine USS Dentuda (SS-335), under the command of Lieutenant Commander John S. McCain Jr., detected high-speed screws at the northern end of the Formosa Strait[2] and at 17:27 identified the vessel by periscope observation as an "I-class submarine" proceeding on the surface at an estimated speed of 16 knots (30 km/h; 18 mph).[3] Dentuda fired four Mark 18 torpedoes at the submarine from her stern torpedo tubes at 17:30 at 24°54′N 119°50′E, but all four missed, and Dentuda noted that the submarine showed no sign of her crew realizing that she was under attack.[3][4] Dentuda pursued the submarine,[3] but lost contact with it in the Formosa Strait at 23:30 at 25°53′N 120°22′E.[4][5] Commander-in-Chief, United States Pacific Fleet analysts concluded that the submarine Dentuda attacked was I-351.[4]

Later in her voyage to Singapore, I-351′s air search radar broke down on 5 July 1945, but she arrived at Singapore without further incident on 6 July.[1] At Singapore, I-351 loaded 132,000 US gallons (500,000 L; 110,000 imp gal) of aviation gasoline and was drydocked from 7 to 10 July 1945.[1] After embarking 42 aviators from the 936th Kōkūtai — an Imperial Japanese Navy Air Service antisubmarine warfare and convoy escort unit of the 13th Air Fleet — for transportation to Japan, she departed Singapore bound for Sasebo on 11 July 1945.[1]

On 14 July 1945, I-351 was proceeding northeast on the surface in the South China Sea east-northeast of Natuna Besar and northwest of Borneo, zig-zagging on base course 035 at 14 knots (26 km/h; 16 mph), when the U.S. Navy submarine USS Blower (SS-325), also on the surface, detected her on radar at 23:56.[1] Blower detected pulses from I-351′s radar at 00:30 on 15 July 1945 and submerged to attempt an attack.[1] At 02:15, Blower fired four Mark 18-2 torpedoes in two spreads at 05°36′N 109°37′E.[1] The first two torpedoes hit I-351 but did not explode, and the second spread of two missed.[1] I-351 submerged and broke contact with Blower, but Blower radioed the nearby submarine USS Bluefish (SS-222) to alert her to I-351′s presence.[1]

I-351 surfaced to continue her voyage.[1] At 03:14 on 15 July 1945, Bluefish detected her on radar 100 nautical miles (190 km; 120 mi) east-northeast of Natuna Besar.[1] At 04:11, Bluefish fired four Mark 14-3 torpedoes at I-351 at a range of 1,850 yards (1,690 m).[1] Two of them hit, and I-351 exploded, broke in two, and sank by the stern at 04°30′N 110°00′E.[1] On the morning of 15 July 1945, Bluefish picked up three survivors from the water, all lookouts from I-351.[1] They identified their submarine as I-351 to Bluefish′s crew and reported that I-351 had been making 10 knots (19 km/h; 12 mph) when they sighted Bluefish′s torpedoes.[1] One of the torpedoes passed ahead, one missed astern, one hit I-351 amidships, and one hit her in the stern.[1] They said that one of the torpedoes struck I-351 in her aviation gasoline tank, causing a huge explosion which knocked them unconscious and blew them overboard.[1] They said they had regained consciousness in the water and been in the water for about four hours when Bluefish rescued them.[1]

The three lookouts were I-351′s only survivors, and a total of 110 men — the other 68 members of her crew and all 42 aviators aboard as passengers — died in her sinking.[1] On 31 July 1945, the Imperial Japanese Navy declared I-351 to be presumed lost with all hands in the South China Sea.[1] She was stricken from the Navy list on 15 September 1945.[1]

• US Dentuda (SS335), Report of War Patrol Number ONE, SS335A9, 29 July 1945.