was the seventh Type C cruiser submarines built for the Imperial Japanese Navy. Commissioned in July 1944, she operated as a kaiten manned suicide attack torpedo carrier during the final year of World War II. Surrendered at the end of the war, she was scuttled by the United States Navy in 1946. It is sometimes considered as part of a sub-class the Type C due to the various designs variations of the latter batch.
Design and description The Type C submarines were derived from the earlier Kaidai-type VI with a heavier torpedo armament for long-range attacks. They displaced surfaced and submerged. The submarines were long, had a beam of and a draft of . They had a diving depth of .Bagnasco, p. 192
For surface running, the boats were powered by two diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a electric motor. They could reach on the surface and underwater.Chesneau, p. 201 On the surface, the C1s had a range of at ; submerged, they had a range of at .
The boats were armed with eight internal bow torpedo tubes and carried a total of 20 torpedoes. They were also armed with a single /40 deck gun and two single or twin mounts for Type 96 anti-aircraft guns. They were equipped to carry one Type A midget submarine aft of the conning tower.Carpenter & Dorr, p. 104
Construction and commissioning
Ordered under the Rapid Naval Armaments Supplement Programme and built by the Sasebo Naval Arsenal at Sasebo, Japan, I-47 was laid down on 21 November 1942 with the name Submarine No. 377. She was numbered I-47 and provisionally attached to the Yokosuka Naval District on 31 July 1943. Launched on 29 September 1943, she was completed and commissioned on 10 July 1944.
Service history
Upon commissioning, I-47 was attached formally to the Yokosuka Naval District. From July through September 1944, she was assigned to Submarine Squadron 11 in the 6th Fleet for work-ups in the Iyo-nada. On 8 October 1944, she was reassigned to Submarine Division 15 in the 6th Fleet, and during October she was configured to carry four kaiten manned suicide attack torpedoes on her after deck, two of them with access tubes that allowed their pilots to enter them while she was submerged. She conducted kaiten launch exercises in Tokuyama Bay from 29 to 31 October 1944, and on 6 November 1944 embarked four kaitens at Otsujima Naval Base.
First kaiten mission On 7 November 1944, the commander-in-chief of the Combined Fleet, Admiral Soemu Toyoda, and the commander of the 6th Fleet, Vice Admiral Shigeyoshi Miwa, visited Otsujima to see off the kaiten pilots. On 8 November 1944, the Kikusui-tai Kaiten Group — made up of I-47 and the submarines and — got underway from Otsujima to conduct the first kaiten operation. Plans called for I-37 to target an American fleet anchorage at Palau with kaitens, while I-36 and I-47 were to carry out a kaiten attack on the U.S. anchorage at Ulithi Atoll in the Caroline Islands, then proceed to Leyte Gulf to attack Allied ships with conventional torpedoes. On 16 November 1944, the submarines received a report from a Nakajima C6N1 Saiun ("Iridescent Cloud"; Allied reporting name "Myrt") reconnaissance aircraft which made a high-altitude flight over Ulithi Atoll and sighted four fleet aircraft carriers and three battleships as well as cruisers and destroyers in the north central part of the lagoon and transports, oilers, and other ships in the south-central part.
By the evening of 18 November 1944, I-47 was west of Ulithi, and she began her approach to the atoll from the southwest. She surfaced off Ulithi at dawn on 19 November and moved in at to only off the atoll, observing over 200 ships in the anchorage. She surfaced again at 00:30 on 20 November 1944, and between 03:28 and 03:42 launched all four of her kaitens. At 05:47, one of them hit the U.S. Navy fleet oiler , which caught fire, capsized, and sank at 09:28. I-47 then withdrew on the surface at to head for her patrol area in Leyte Gulf. After she transmitted a report of the sinking of Mississinewa on 22 November, however, she and I-36 received orders on 24 November to return to Japan rather than proceed to Leyte Gulf. After stopping at Otsujima, the two submarines arrived at Kure, Japan, on 30 November 1944.
On 2 December 1944, over 200 staff officers and specialists convened aboard the 6th Fleet flagship Tsukushi Maru to evaluate the results of the kaiten attack on Ulithi Atoll. After examining after-action reports and post-attack reconnaissance photographs, they credited the attack with sinking three aircraft carriers and two battleships. In fact, the attack had sunk only Mississinewa.
Second kaiten mission
On 8 December 1944, I-47 was assigned to the Kongo ("Steel") Kaiten Group along with the submarines I-36, , , , and for an attack scheduled for dawn 11 January 1945 on five different U.S. anchorages in widely separated locations; the date of the attack later was postponed to 12 January 1945. She got underway on 25 December 1944 bound for her target, Hollandia on the coast of New Guinea. On 30 December 1944, during her voyage, she rescued eight starving Imperial Japanese Army soldiers from a raft in the Philippine Sea west of Guam; the soldiers had participated in a failed attempt to storm the U.S. airfield on Guam and then escaped the island aboard the raft, drifting at sea for 32 days before I-47 found them.
On 8 January 1945, an Imperial Japanese Army Air Force reconnaissance aircraft flew over the Hollandia area and sighted 40 large transports anchored in Humboldt Bay () and 10 smaller vessels outside the anchorage, and the Japanese passed this report to I-47. I-47 sighted Cape Soeadja on the north coast of New Guinea at 10:30 on 11 January 1945, then proceeded north. After dark, she surfaced off New Guinea to recharge her batteries. She sighted a U.S. hospital ship, which passed without noticing I-47, then headed south at 23:30 to reach her launch position off Humboldt Bay.
Submerged, I-47 reached the launch area north of Cape Soeadja by 03:00 on 12 January 1945. She launched all four kaitens between 04:14 and 04:30, then surfaced and departed the area at flank speed. In Humboldt Bay, one kaiten grazed the port side of the anchored Liberty ship below the waterline, causing a small leak in her No. 3 hold. The kaiten then exploded about off Pontus H. Ross′s port bow at 05:21, causing additional minor damage to her hull. A few seconds later another explosion took place off Cape Soeadja. At sea, I-47 noted a column of red fire rising from the direction of Humboldt Bay after 05:20. She reached Kure on 1 February 1945. During a conference aboard Tsukushi Maru on 7 February 1945, the 6th Fleet's staff credited I-47′s kaitens with sinking four transports at Humboldt Bay.
February–March 1945
During I-47′s stay at Kure, her deck gun was removed and she was equipped to accommodate two more kaitens in its place, raising her kaiten-carrying capability to six. She suffered an accident on 16 March 1945 in which a member of her crew died of carbon monoxide poisoning while she was carrying out kaiten launch exercises in the Seto Inland Sea off Hikari. On 20 March 1945 she conducted combat exercises in the Seto Inland Sea with the submarines I-36, , I-53, I-56, and I-58.
On 27 March 1945, I-47 was selected to lead the Tatara Kaiten Group in an attack on American ships off Okinawa. After loading provisions for two months and 20 torpedoes at Kure, she departed on the morning of 28 March 1945 and moved to Hikari, where she embarked six kaitens. She conducted diving tests with the six kaitens aboard on 29 March 1945, then returned to Hikari and embarked the kaiten pilots.
Third kaiten mission
I-47 got underway from Hikari on the afternoon of 29 March 1945, heading through the Bungo Strait on the surface at under the escort of the submarine chaser . About two hours after she rendezvoused with CHA-200, American carrier aircraft attacked the two ships in the Sea of Hyūga off Kyushu at around 16:00, forcing I-47 to crash-dive and sinking CHA-200. I-47 surfaced after dark, but two American aircraft illuminated the area with flares and attacked her with several depth charges. She survived the attack with only minor damage.
While I-47 was on the surface recharging her batteries south of Kyushu east of Tanegashima at 02:30 on 30 March, she sighted two Allied patrol vessels directly ahead of her and crash-dived. A main ballast tank vent malfunctioned, and she assumed a 50-degree down angle, reaching a depth of before her crew could stop her descent. Her crew finally stabilized her at a depth of . Allied vessels pursued her for the next 11 hours, during which one of her periscopes and one of her fuel tanks developed leaks and her internal temperature rose to .
After finally breaking contact, I-47 surfaced south of Tanegashima and headed south, but two Allied patrol aircraft sighted her and attacked her, dropping 20 depth charges. I-47 submerged and escaped with only minor additional damage, but her crew found it impossible to stop the leak in her fuel tank. She entered Uchinoura Bay on the coast of Kyushu before daybreak on 31 March 1945 so that her crew could inspect her damage. Her crew found an unexploded depth charge on her bridge and damage to her outer hull above her ballast tanks and to her anti-sonar coating. After reporting the damage to 6th Fleet Headquarters she received orders to abandon her mission and return to Hikari, which she reached on 1 April 1945. After disembarking her kaitens there, she proceeded to Kure for repairs. Arriving there on 2 April, she was drydocked until 15 April 1945.
Fourth kaiten mission
With her repairs complete, I-47 departed Kure on 17 April 1945 bound for Hikari. There on 20 April 1945 she and I-36 formed the Tenmu ("Heavenly Warriors") Kaiten Group, each carrying six kaitens, with orders to attack Allied sea lines of communication between Okinawa, Ulithi Atoll, and the Mariana Islands. Bound for the waters east of Okinawa, I-47 got underway from Hirao on 22 April 1945. During her voyage, she was on the surface recharging her batteries on 23 April 1945 when her radar detector picked up a radar signal and she submerged. She avoided attack, but when she surfaced she sighted a sonobuoy apparently dropped by an American patrol plane that had been searching for her.
I-47 arrived in her patrol area southeast of Okinawa on 26 April 1945. Her starboard diesel engine immediately broke down, and her crew began repairs. She received a radio message from I-36 on 27 April 1945 in which I-36 reported a successful kaiten attack on an Allied convoy. I-47′s crew completed repairs to her engine on 28 April 1945.
On 1 May 1945, I-47 was south-southwest of Okidaitōjima when she detected an Allied convoy on radar at a range of . She closed the range and launched three kaitens at a range of , subsequently hearing large explosions. On 2 May, she was south-southwest of Okidaitōjima when she sighted a 10,000-ton tanker heading northwest at escorted by two destroyers. She launched a kaiten five minutes later, and subsequently heard two heavy explosions. Her sound operator then heard the propeller noises of two destroyers, and at 11:20 I-47 launched another kaiten. I-47 temporarily lost sound contact with the kaiten, but then heard high-speed propellers, followed by a heavy explosion. I-47 then departed the area at flank speed, heading southeast.
On 7 May 1945, I-47 detected what she identified as a British Leander-class light cruiser south-southwest of Okidaitōjima on radar. She launched a kaiten and reported a hit on the cruiser. She could not launch her two remaining kaitens because of malfunctioning torpedoes, and the 6th Fleet ordered her to return to Hikari, which she reached on 12 May 1945. After disembarking her two kaitens and their pilots, she got back underway and arrived at Kure on 13 May 1945.
May–July 1945