I-38 was an Imperial Japanese Navy B1 type submarine. Completed and commissioned in 1943, she served in World War II, operating on supply missions in the New Guinea campaign and the Solomon Islands campaign, and conducting war patrols in the Solomons, off the Mariana Islands, and in the Philippine Sea before she was sunk in November 1944.
Construction and commissioning
I-38 was laid down on 19 June 1941 in the Sasebo Navy Yard at Sasebo, Japan, with the name Submarine No. 151. Renamed I-38, she was launched on 15 April 1942 and provisionally attached to the Kure Naval District. She was completed and commissioned on 31 January 1943.
Service history January–May 1943 Upon commissioning, I-38 was attached formally to the Kure Naval District and assigned to the Kure Submarine Squadron. The same day, she got underway to participate in tests of a new type of shallow-depth torpedo in the Seto Inland Sea. After that, she conducted tests of the new Unpoto gun sled, a sled that could carry up to 15 tons of cargo, usually in the form of three Type 96 howitzers and ammunition for them. She became the first Japanese submarine equipped with fittings to carry an Unpoto. She participated in torpedo practice with the submarines , , and on 26 March 1943. On 1 April 1943 she was assigned to Submarine Squadron 11 for work-ups.
With her work-ups completed, I-38 was reassigned to Submarine Division 15 in Submarine Squadron 1 on 30 April 1943. On 8 May 1943, she got underway from Kure with an Unpoto on her afterdeck, paused at Osako, then continued to Saeki, where she spent the night of 8–9 May 1943. She departed Saeki on 9 May with the Unpoto in tow bound for Truk, which she reached on 14 May 1943. During her stay at Truk, the commander-in-chief of the 6th Fleet, Vice Admiral Teruhisa Komatsu, inspected I-38 and her Unpoto installation on 15 May, after which I-38 unloaded her provisions and a repair ship moored alongside her to repair the Unpoto. She was assigned to the Southeast Area Fleet that day. departed for Rabaul on New Britain on 16 May 1943.
New Guinea campaign, May–June 1943
Assigned to supply runs to New Guinea in support of Japanese forces fighting in the New Guinea campaign, I-38 arrived at Rabaul on 18 May 1943. There she detached her Unpoto and transferred some of her provisions to the submarine tender , and her commanding officer boarded Chōgei to receive a briefing on the supply operations from the commander of Submarine Squadron 7. On 19 May, she conducted an Unpoto test with the commanders-in-chief of the Southeast Area Fleet, Vice Admiral Jinichi Kusaka, and Eighth Area Army, General Hitoshi Imamura, looking on. She then transferred all remaining provisions in her after storeroom and all but four of her torpedoes to Chōgei.
On 21 May 1943 I-38 set out from Rabaul on her first supply run, bound for Lae on the coast of New Guinea carrying 12 naval officers as passengers and a cargo of 48.6 tons of ammunition and provisions. She arrived at Lae on 23 May, quickly discharged her passengers and cargo, embarked 17 sick and wounded Imperial Japanese Army soldiers, and got back underway for Rabaul. Soon after she departed Lae, a United States Navy PT boat sighted her and fired six torpedoes at her, but they all missed, and I-38 arrived safely at Rabaul on 25 May 1943.
I-38 got underway from Rabaul on 27 May 1943 for her second supply run, carrying 29 Special Naval Landing Forces personnel and a cargo of 48.6 tons of food and medicine. As she approached Lae on 28 May, her lookouts sighted a U.S. Navy PT boat, and she dived to avoid it. That night she dropped off her passengers and cargo, brought aboard six soldiers, and headed back for Rabaul, where she arrived on 31 May 1943. After taking aboard cargo from Goshu Maru, she left Rabaul on her third supply run on 2 June and met a Daihatsu-class landing craft off Lae on 4 June, transferred her cargo to it, embarked General Imamura and three members of his staff for transportation to Eighth Area Army headquarters at Rabaul, and headed back to Rabaul, arriving there on 6 June 1943.
At Rabaul, I-38 loaded cargo from Taisei Maru and an Unpoto sled was mounted on her afterdeck. She departed on 9 June 1943 and headed for New Guinea, discharging some of her cargo at Salamaua on 11 June 1943, then proceeding to Lae, where on 12 June she unloaded the rest of it and disembarked her Unpoto, the first successful delivery of artillery using an Unpoto. She embarked six soldiers, and soon after she left Lae on her return voyage to Rabaul, an Allied plane spotted her and dropped three bombs after she crash-dived. She avoided damage, but another Allied plane forced her to crash-dive again at around midnight. She arrived safely at Rabaul on 13 June 1943.
I-38 refueled from the oiler at Rabaul on 15 June 1943 and received a new Unpoto sled from Taisei Maru on 17 June. She began her fifth supply run on 19 June, departing Rabaul with 48.5 tons of provisions aboard, calling at Lae to unload them on 21 June, and returning to Rabaul on 23 June 1943. After receiving another new Unpoto from Taisei Maru on 24 June and undergoing maintenance work and having her upper deck repainted on 25 June 1943, I-38 departed on her sixth supply run on 26 June 1943, calling at Lae after dark on 28 June to unload 48.5 tons of provisions and embark 15 soldiers, and then made for Rabaul, which she reached on 30 June 1943.
First war patrol
After taking aboard supplies from Chōgei on 1 July 1943, I-38 departed Rabaul on 2 July on her first war patrol, ordered to attack Allied shipping in the Solomon Islands, where Japanese forces were fighting in the Solomon Islands campaign, and conduct a reconnaissance of Kula Gulf. She arrived in her patrol area on 4 July, and on 5 July sighted two Allied transports, but was unable to attack them. On 6 July, she fired a torpedo at a U.S. Navy destroyer, but it missed.
I-38 was on the surface in darkness in New Georgia Sound on 7 July 1943, when an Allied warship — probably the destroyer at — surprised her, suddenly opening fire with her main gains and machine guns. I-38 crash-dived, and 10 minutes later the warship dropped a pattern of depth charges. I-38 descended to a depth of and finally broke contact with the warship after 90 minutes.
I-38 conducted her reconnaissance of Kula Gulf on 8 July, again after dark on 9 July, and a final time on 10 July 1943, when she received orders to return to Rabaul to resume her New Guinea supply runs. During her voyage to Rabaul, Allied aircraft attacked her repeatedly on 11 July 1943, forcing her to crash-dive each time, but she arrived safely at Rabaul on 12 July 1943.
New Guinea campaign July–August 1943
On 17 July 1943, I-38 began her seventh New Guinea supply run from Rabaul, calling at Lae on 19 July and reaching Rabaul safely on 21 July despite coming under frequent attack by Allied bombers during her return voyage. She received a new Unpoto sled and cargo on 23 July and made her next round trip between Rabaul and New Guinea from 24 to 28 July 1943, discharging cargo at Lae on 26 July. On her ninth trip, conducted between 30 July and 3 August 1943, she lost five or six supply drums overboard while outbound from Rabaul, but she dropped off the rest of her cargo at Lae on 2 August 1943. On her tenth run, she departed Rabaul on 6 August 1943, called at Lae on 8 August, and crash-dived during her return trip after her lookouts sighted an Allied plane on 9 August, but returned safely to Rabaul on 10 August 1943.
New Guinea and Solomon Islands
After taking aboard cargo from Nagoya Maru on 12 August 1943, I-38 departed Rabaul on 14 August on her eleventh supply run and first to the Solomon Islands, carrying cargo to Kolombangara. She was only about into her voyage that day when an Allied plane bombed and strafed her. On 15 August, six Allied aircraft attacked her in darkness and depth-charged her. She nonetheless unloaded her cargo at Kolombangara on 17 August. During her return voyage to Rabaul, her lookouts sighted six United States Army Air Forces B-24 Liberator bombers on 19 August and she crash-dived, but she made it back to Rabaul on 20 August 1943.
I-38 received a new Unpoto from Toyo Maru on 26 August 1943. For her twelfth supply trip, she returned to the New Guinea run, departing Rabaul on 28 August, calling at Lae on 30 August, and then making for Rabaul. En route, she had to crash-dive several times on 1 September 1943 when Allied aircraft sighted her, but she reached Rabaul that day.
After receiving another new Unpoto from Toyo Maru on 2 September, I-38 set out for her second trip to Kolombangara on 7 September 1943. While she was entering the Kolombangara Gulf, an Allied aircraft attacked her with a bomb but missed. Rather than unload her cargo at Kolombangara, she proceeded to Shortland Island, where she unloaded it on 12 September 1943 and got back underway for Rabaul. Only 30 minutes into her return voyage, her lookouts sighted an Allied plane, and she crash-dived. She was back on the surface again at 23:00 when an Allied plane surprised her — I-38′s crew reporting that the plane had switched off its engine to approach I-38 silently — and dropped three bombs, all of which missed. I-38 arrived at Rabaul on 13 September 1943.
New Guinea campaign, September–December 1943
I-38 resumed her focus on supplying the New Guinea campaign. After taking aboard a cargo of provisions from Toyo Maru on 17 September 1943, she got underway with the commander of Submarine Division 15 embarked on her fourteenth supply run to deliver supplies at Finschhafen on the Huon Peninsula. She arrived off Finschhafen on 22 September but could not make contact with the Imperial Japanese Army garrison ashore and moved back out to sea. She again approached Finschhafen after dark on 23 September and again failed to contact the soldiers on the coast, and later that night she sighted an Allied convoy but was unable to attack it because of the cargo she still had aboard. She made a third and final attempt to contact the Japanese forces ashore on 24 September, and when that failed as well she received orders to patrol in the area until 27 September and then deliver her cargo at Sarmi, New Guinea. After dropping off half her cargo at Sarmi on 27 September, she returned to Rabaul on 28 September 1943.
On 3 October 1943, I-38 began her fifteenth supply run, departing Rabaul bound for Sarmi. While she was unloading at Sarmi on 5 October, an Allied plane attacked her, forcing her to submerge with two-thirds of her cargo still on her deck. She soon surfaced, completed unloading, and began her return trip to Rabaul, where she arrived on 8 October 1943.
While at Rabaul, I-38 began tests of the Unkato supply container — a submersible cargo container that could carry up to 377 tons of supplies, designed for a one-way trip in which the cargo′s recipients released, recovered, and unloaded it — on 10 October 1943. On 12 October 1943, the U.S. Army Air Forces Fifth Air Force and the Royal Australian Air Force combined to stage the largest Allied air raid of the Pacific War up to that time, with 349 aircraft based in New Guinea and Australia hitting Japanese airfields around Rabaul and shipping in Simpson Harbour at Rabaul. I-38 and the submarines , , , Ro-105, and were in the harbor during the air raid and most of them submerged to avoid attack. I-38 concluded her unsuccessful Unkato tests on 13 October 1943.