Japanese Midget Submarine Operations 1942-45 II

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HA69 “Hei-Hyoteki C” midget submarine on board of landing ship 5-go 8/1944.


By the end of 1942, the Imperial Japanese Navy worked to redesign and redeploy the kō-hyōteki. Unfortunately for Japan, this effort focused on the technical deficiencies of the submarines instead of focusing on the misuse of the craft and crews on ill-suited missions. Private doubts plagued naval leaders and doubtless some of the veterans of the corps, but the program pushed on. As the last group of Type A submarines was completed, a new sub, numbered HA-53, was designed and laid down in October 1942 and completed in February 1943 with a major difference. Less than a third of a meter (1 foot longer than the Type A boats), its extra space accommodated a 40 hp, 25 kilowatt diesel generator to recharge the sub’s batteries, thus correcting the major design inefficiency of the earlier midgets. From this prototype, called an otsu-gata (Type B), a new group of hei-gata (Type C) boats emerged (Itani et al. 1993:127). These 81-foot-long, 49 ton craft carried a crew of three, the third man serving as the engineer. More complex than their predecessors, the hei-gata began to emerge from the factory in the summer of 1943, with five modified kō-hyōteki, HA-49, HA-50, HA-51, HA-52, and HA-53 rebuilt as Type C boats.

The Imperial Japanese Navy decided to ship these five submarines to the Bismarck Archipelago (now in Papua New Guinea) to be based at the former Australian base at Rabaul, which was now a heavily built up and fortified Japanese bastion after its January 1942 capture. As supply convoys ferried supplies and personnel and towed a supply and support vessel for the midget submarines, the submarines were readied for towing across the Pacific. Only two of the five would arrive, the first being HA-53, which reached Rabaul on December 16, 1943, under tow of the merchant ship Hidaka Maru. HA-52 arrived under tow of the support ship Sanko Maru, which steamed from Palau with the sub on February 12, 1944. Diverted to Kavieng, New Ireland, Sanko Maru and HA-52 arrived at Three Islands Harbor, New Hanover, in time for a US aerial assault on February 16 that sent the ship to the bottom. Strafed and straddled by near misses from bombs, HA-52 was scuttled by the crew after the second day of attacks on February 17. The other midgets fared no better. The submarine USS Seawolf sank the tanker Yamazuru Maru, towing HA-50, on January 14, 1944. The submarine USS Whale sank Tarushima Maru, towing HA-51, on January 17, 1944. Finally, the ship Neikai Maru, towing HA-49, was sunk by aircraft January 28, 1944 (Cressman 2000:205, 208). With only HA-53 at Rabaul, there was to be no effective midget submarine force in the Bismarcks. The base itself, heavily bombed and strafed throughout the first months of 1944, was left cutoff and mauled until the end of the war. When surviving Japanese forces surrendered on September 6, 1945, they scuttled HA-53 in shallow water.

Japan was withdrawing from the South Pacific. A lack of fuel led the Sixth Submarine Fleet to withdraw from Truk in the spring of 1944. The navy sent the beleaguered garrison at Saipan some of the new kō-hyōteki. Again, they made no appreciable difference. Two boats out of five towed there were lost at sea, and the other three and their crews vanished in the destruction of Japanese forces who massed for one last banzai charge during the island’s invasion. In the aftermath of the battle for Saipan, one of the submarines was discovered in 60 feet of water, raised for inspection, and then scuttled (Commander Surface Squadron Twelve 1944:12). The sad legacy of the midget submariners, begun at Pearl Harbor, continued to be one of needless sacrifice.

Ten of the new Type C boats were sent to the Philippines on D-type destroyer transports in 1944. Based in the southern Visayas at Davao, Cebu, and Zamboanga, the midgets were commanded by Captain Kaku Harada, one-time skipper of Chiyoda and the “father” of the program. Hammered by American attacks, the bases were abandoned in favor of Cebu, where Harada was located at the end of the war at the 33rd Naval Special Base (Smith 1991:609). There the last of the midgets fought to the close of the Philippine campaign from an advance base at Dumaguete at the southern side of Negros Island, where they sortied to ambush US forces coming through Surigao Strait into the Mindanao Sea.

While the Japanese claimed to have sunk a destroyer with a midget attack on December 8 and two transports on December 18 in Ormoc Bay, the reports were false. Another Japanese claim that a later, newly developed Type D sub sank a cruiser and four cargo ships in early 1945 likewise is not supported by either Japanese or US records. The United States, however, did sink a submarine in Ormoc Bay on November 28, 1944, and while the target was listed as a possible I-boat, it may well have been a midget. Another of the Cebu-based midgets was definitely lost when it was stranded in December (Holmes 1966:398). The Cebu midgets were the last Japanese submarine forces left in the Philippines by February 1945. A plan to send the larger submarine RO-43 to Cebu with torpedoes and supplies for the midgets was called off by naval headquarters; the midgets, as always, were expendable.

An attack on USS Boise (CL-47) on January 5, 1945, as it approached Luzon by three midgets was met by the destroyers USS Nicholas (DD-449) and Taylor (DD-468). Boise executed an emergency turn and evaded a torpedo by maneuvering “radically at high speeds” (Commanding Officer, USS Boise 1945). An escorting TBF aircraft from a nearby carrier spotted one sub, and a well-placed bomb drove it to the surface, where Taylor rammed and depth charged it, sending the kō-hyōteki and its crew to the bottom (Commanding Officer, USS Boise 1945). The other two midgets escaped, reporting back in Cebu they had sunk an American destroyer and one other warship (Rohwer 1983:287). The midgets based at Dumaguete waged a bitter war against the US Navy through March, reporting various unverified successes and one successful attack. In what was likely an attack by a Dama-guete-based midget on February 21, the destroyer USS Renshaw (DD-499) was hit with a single torpedo while escorting landing ships and craft through Surigao Strait. The torpedo tore into the destroyer, killing nineteen of the crew. The ship’s log reported: “Ship is dead in the water. Examination shows that forward engine room and the after fire room are completely flooded and open to the sea. The bulkhead between the after fire room and after engine room is intact but bulging aft about one foot. There are numerous leaks from bulkhead ruptures where cable pass through the bulkhead that are slowly leaking and flooding the after engine room” (Renshaw Log, February 21, 1945).

Drifting without power, Renshaw engaged the midget with a 40 mm antiaircraft gun. The midget escaped, and after starting an emergency generator, and with assistance of other ships, Renshaw survived.

In March, as troops landed at Cebu, the destroyers USS Conyngham (DD-371) and Flusser (DD-368) encountered another midget and bracketed it with shells, but it escaped. The next morning, however, the destroyer Newman (DE-205) spotted a midget some 7 miles south of the previous day’s encounter. Approaching the sub, Newman’s crew opened fire with automatic weapons, reporting they had struck the conning tower and possibly sank it (Morison 1963:236). It was the end of the kō-hyōteki force at Cebu; the remaining three subs were scuttled, and the base and sub crews joined land forces defending Cebu (Willoughby and Prange 1994:548, n. 72; Vego 2006:298). When the battle ended, the Japanese lost 5,500 men, and another 8,500 troops surrendered (Smith 1991:617).

The summer of 1944 also saw the Japanese send a force of eleven Type C boats to Okinawa. A base at Unten Ko, a small village on the north shore of the Motubu Peninsula, on the northwest shore of the island, housed them in a tiny harbor in the lee of two small offshore islets, Kouri and Yaguchi (Appleman et al. 1948:142–43). The base also housed a torpedo depot and four squadrons of explosive-packed Shinyo suicide boats. The base’s presence was known to US forces, and an aircraft carrier strike on October 10, 1944, hit it and sank at least two midgets and the depot ship, the 5,160 ton Jingei. A later report claimed that four midgets were sunk in the attack (Appleman et al. 1948:45). This may be true, for by March 1945, only six operational midgets remained, three of which sortied on March 25 to attack TF 54, the Okinawa bombardment force. Only one of the kō-hyōteki, HA-67, returned, its crew claiming their torpedoes hit an “enemy battleship.” The attack may have been on the destroyer USS Halligan (DD-584). On March 26, while patrolling off Okinawa, the bow of the destroyer exploded, with the forward half of the ship literally disintegrating, killing 160 of the 327-man crew. The badly damaged ship drifted ashore and was a total loss. US Navy accounts state Halligan struck a mine, but the commander of HA-67 reported he fired two torpedoes at a ship that exploded on that date. If true, it was the only midget submarine success at that stage of the war (Stille 2014:44). On the same day, however, the minesweeper USS Strength (AM-309) reported it came under attack from a partially submerged midget submarine, which fired its torpedoes but missed. In the confusion of the battle and the loss of most of the Japanese contingent and records, the reality of the role of the midget submarines in the battle for Okinawa will likely never be known.

On that same day, the cruisers USS Wichita (CA-45), Biloxi (CL-80), and St. Louis (CL-49) reported spotting torpedo tracks in the morning. USS Callaghan (DD-792) definitely accounted for one of the midgets that day. While screening the battleship USS New Mexico (BB-40), the destroyer’s crew noticed “a small periscope . . . about 35 yards to port and abreast the bridge” (Commanding Officer, USS Callaghan 1945). The destroyer went hard to port and depth charged the area, blowing the sub to the surface. Rolling on its side, the sub sank. Callaghan kept depth charging until an oil slick and pieces of wood from the midget’s interior rewarded their efforts (Commanding Officer, USS Callaghan 1945).

Another midget attacked the transport USS Catron (APA-71) on April 5, but the torpedo missed the ship and exploded on the reef. The following day, the last operational submarine at Okinawa was scuttled, and the base and sub crews joined the naval forces of Rear Admiral Minoru Ota and the land forces of General Mitsuri Ushijima’s 32nd Army for a last-ditch fight to the death with the invading US forces. The base at Unten Ko was cut off and isolated on April 7, when the 29th Marines reached Nago and isolated the Motobo Peninsula. The Marines discovered twenty-one sub pens and six destroyed midgets when they reached the base, another tangible reminder of the failure of a once-vaunted program and its craft (Dyer 1972:1100).

After the fall of the island, and the death of most of its defenders, a small group of seven of the kō-hyōteki corps joined fifteen infantry soldiers in an attempt to escape to Japan. Pushing off from Okinawa in a small barge in early August, they drifted through the islands without food and water for 3 weeks, strafed on occasion by American planes. Eight survivors were reportedly rescued on August 18 by an unnamed US submarine (Warner and Seno 1986:194–95).

Forschungsmitarbeiter Mitch Williamson is a technical writer with an interest in military and naval affairs. He has published articles in Cross & Cockade International and Wartime magazines. He was research associate for the Bio-history Cross in the Sky, a book about Charles ‘Moth’ Eaton’s career, in collaboration with the flier’s son, Dr Charles S. Eaton. He also assisted in picture research for John Burton’s Fortnight of Infamy. Mitch is now publishing on the WWW various specialist websites combined with custom website design work. He enjoys working and supporting his local C3 Church. “Curate and Compile“
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