Japanese Midget Submarine Operations 1942-45 I


“Ko-Hyoteki” midget submarines. One of the scuttled and abandoned kō-hyōteki in the shallows in the Solomons, 1942.

As the I-boats and midget submarines of the second special attack flotilla sortied to the Indian ocean and Australia, Japanese naval planners were hard at work assessing the next major fleet operation, a massive naval strike at Midway and the Aleutians, to seize the islands and establish an eastern defensive perimeter for japan, as well as provide a base for closer strikes at Hawaii. As part of the planning for Midway, both Chiyoda and Nisshin, each loaded with twelve kō-hyōteki, steamed behind the strike force to establish a midget submarine base at Kure Atoll (Parshall and Tully 2007:48–49, 453; Spennemann 2013). Defeat at Midway scuttled those plans, and the unscathed tenders returned to Japan with their midgets.

While Midway was an unmitigated failure, the feint to the north and the seizure of the western end of the Aleutian chain established garrisons on the islands of Attu and Kiska. Japanese troops waded ashore on Kiska on June 7, 1942, quickly capturing the island’s two-man radio station crew. Attu was also quickly taken with no resistance. In the aftermath of the Midway disaster, the Japanese decided to hold their tenuous position in these barren, windswept islands. It was not necessarily a tactical advantage, but it posed a psychologically strategic value. Thousands of troops, materiel, and additional weapons were shipped to Attu and Kiska, each respectively 650 and 800 miles from Japan’s northern shores. In the months that followed the seizure of the islands, the Japanese constructed coastal and antiaircraft defenses, a seaplane base, camps, roads, and an airfield (Chandonnet 2008; Garfield 1995).

As part of the fortification program, the navy sent Chiyoda to Kiska. The ship carried six kō-hyōteki and landed them on the island on July 4, 1942. The midgets augmented Kiska’s defenses, which now included a large garrison, five hundred civilian laborers, seacoast guns, and the support of twelve I-class submarines. Naval engineers built a 30-foot-wide, 200-foot-long submarine pen and launching facility for the midgets on the edge of Kiska harbor. It included several buildings—a machine shop, a battery repair shop, an acid storage building (for the batteries), an equipment storage building, and a powerhouse with a diesel generator. The sub pen was set inside a concrete-lined excavation cut into the shore, with two sets of 6-foot-wide narrow gauge track. Steel cradles held the subs, which were winched ashore. The pen was covered by a large wooden truss roof (Payne 1943:34). The first midget base outside of Japan, the new facility represented the navy’s return to the original concept of the midgets as shore-based, coastal defense weapons.

However, the kō-hyōteki were never used in Aleutian combat. The occupation of the islands resulted in a furious response from the United States, which began a year-long campaign to oust the Japanese. Aerial bombardment and harassment was followed by a naval campaign to interdict the flow of supplies by sea. The midget base was damaged in a September 14, 1942, air raid launched from Adak Island that sank vessels in the harbor and strafed the submarines. Later raids bombed the base, destroying the power plant, and one of the midgets was put out of commission by a fragmentation bomb that peppered and pierced the aft hull. Attu was taken by a joint American and Canadian invasion force in May 1943, and most of the occupation force died in the battle and a last-ditch suicidal banzai charge that saw nearly a thousand Japanese die. In the aftermath of the retaking of Attu, Japan gave the order to evacuate Kiska, and on July 28, under the cover of weather, ships loaded 5,183 men and headed home. The midget corps, before departing, set off the scuttling charges in their last three, relatively undamaged kō-hyōteki. When the allied invasion force landed on Kiska on August 15, they found a deserted island filled with abandoned buildings and destroyed equipment, including the wrecked midgets (Coyle 2014:101–10).


After the defeat at Midway and the ill-fated Aleutians venture, the Imperial Japanese Navy still hoped that the kō-hyōteki could play an important role in the war. In late 1942, the number of kō-hyōteki constructed stood at forty-four; of these, at least a third had been lost along with most of the original class of midget submariners. The corps was about to lose more.

In response to the ongoing struggle in the Solomon Islands, where Japanese and Allied forces continued to wage air, land, and sea battles, the navy decided to deploy some of the kō-hyōteki to that theater. Admiral Ugaki, while an early proponent of the midget program, was uneasy with the decision, noting in his diary on September 30, 1942, that Chiyoda had arrived at Truk from Kure with eleven submarines on board: “According to the skipper who came to report, training and readiness of the craft were still insufficient. I can’t help but feeling we called them down too soon, disregarding these points. We shouldn’t use them unless success is believed certain. Otherwise, judging from past experiences, sacrifices would only be increased for nothing. I warned the staff accordingly and told them to keep on with their training for the time being” (Chihaya 1991:220–21).

By October, the crews were apparently ready, and Chiyoda sailed to the Solomons with six kō-hyōteki designated as the Third Special Attack Unit. The commander of the Third Destroyer Squadron argued for placing the midgets at Lunga or Tulagi, while Combined Fleet staff argued for operating the subs between Guadalcanal and the Russell Islands. Ugaki decided to land the midgets at Guadalcanal, where a base was established for them at the island’s northwest tip, near Cape Esperance, at Kamimbo Bay.

A “Tokyo Express” run on October 11 brought the necessary materials for the base in the destroyer Shirayuki along with 1,100 soldiers (Frank 1990:321–22). Ugaki remained distressed, because although “consideration to giving them a chance to participate in a battle since they were brought down here can be appreciated, what I am afraid of most is that it will only result in belittling human lives and arms, and sending them to certain death, yet bringing no contribution to the outcome of the operation” (Chihaya 1991:234). Nonetheless, Chiyoda delivered eight more submarines in October to Shortland, Bougainville.

A document recovered from a sunken kō-hyōteki in June 1943 outlined the strategy for the midgets: “Plan of Attack against Anchored Enemy Warships for the Kō-hyōteki Based at Guadalcanal: The Time for Resolute Action.” Resolute action meant acting quickly and decisively: “Upon receiving a report that the enemy has been discovered, the attack will be carried out with the least possible delay. Do not lose your opportunity because you vainly delayed and thereby allowed the enemy to escape into a strongly defended harbor” (Plan of Attack 1943). The orders stressed that two midget submarines were to be deployed against a “powerful” enemy ship and that “four or more will not be ordinarily be used simultaneously at one spot,” perhaps because of the possibility of complete loss, as seen in Pearl Harbor, Diego Suarez, and Sydney.

The kō-hyōteki were ordered to remain submerged daily from 30 minutes before sunrise until dusk and then make evening attacks. While exhorted to pick out “the most powerful ship or transport” as a target, midget submariners were given the discretion to expend a torpedo on patrol craft. After attacking, commanders were to take a “suitably circuitous route.” If disabled or out of power, the subs were to be towed to Japanese-occupied islands; if this was impossible, the subs could be scuttled, but the crews were not to commit suicide. These orders saved the lives of five midget crews at Guadalcanal, who were the first members of the kō-hyōteki corps sent into combat who lived to fight another day.

The setting for midget submarine operations in the Solomon Islands was Indispensable Strait between Florida and Malaita islands and Savo Sound between Guadalcanal and Florida islands, with tiny Savo island between them. There, as part of a Japanese plan that deployed RO and I-class submarines to ambush American shipping going up the slot to Guadalcanal, the Imperial Japanese Navy sent I-16, I-20, and I-24, each with a kō-hyōteki, to attack American ships anchored off Guadalcanal in early November 1942.

From a position 5 miles off Cape Esperance, I-20 launched a midget commanded by Sublieutenant Nobuharu Kunihiro and crewed by Petty Officer First Class Goro Inoue at 02:22 on November 7. Two hours later, while patrolling the Lunga anchorage off the southern end of Savo island, Kunahiro avoided destroyers screening the area and continued to Lunga Point. Just before 09:30, Kunihiro and Inoue fired one of their torpedoes at the destroyer USS Lansdowne (DD-486), which was busy unloading mortar ammunition. The torpedo passed astern of Lansdowne, which went into action just as the torpedo struck the nearby transport Majaba (AG-43) “cleanly amidships on the starboard side” (Commanding Officer, USS Lansdowne 1942). Badly damaged, Majaba did not sink, as its crew beached it. Lansdowne, meanwhile, “slipped her chain and swing around with full rudder and emergency full ahead” and pursued an aggressive depth charge attack on the midget, dropping a total of twenty-two depth charges over the next half hour (Commanding Officer, USS Lansdowne 1942). I-20 tou, undamaged, retreated, but a faulty gyrocompass led Kunahiro to strand his sub in shallow water off the beach at Malvovo. After flooding their sub, the two midget submariners escaped—the first in the program to do so (Warner and Seno 1986:165).

Over the course of little more than a month, from November 11 to December 13, seven other sorties resulted in the loss of all seven of the midgets. The first was that launched from I-16 and commanded by Lieutenant (j.g.) Teiji Yamaki and crewed by Petty Officer First Class Ryoichi Hashimoto. Yamaki, a veteran of the first training class, had been scheduled to participate in the Sydney attack, but a battery explosion in his kō-hyōteki killed his crew member and badly burned him. Now recovered, he was back in action, but his mission was cut short when during the launch from the mother sub, his rudder struck the launch cradle and was disabled. Unable to steer, Yamaki surfaced and scuttled his craft but escaped alive, as did Hashimoto, by swimming ashore (Warner and Seno 1986:165). Another midget, launched from I-20 on November 19, developed an oil leak and was scuttled, but its crew, Sublieutenant Yoshiaki Miyoshi and Petty Officer Kiyoshi Umeda, escaped and swam ashore. Their craft may have been one later raised from some 10 meters (30 feet) of water off Cape Esperance on January 4, 1945, by the coast guard buoy tender Ironwood (WAGL-297), which raised and loaded the wreck onto a crane barge and beached it near Hutchinson Creek on Florida island for examination and disarmament by attempting to remove the torpedoes. After what was reported as a “thorough search,” with the torpedoes still stuck in their tubes, the sub was scuttled off to Gavutu island (Commanding Officer, USCG Ironwood 1945).

The next midget loss was commanded by Lieutenant Yasuki Mukai and crewed by Petty Officer First Class Kyugoro Sano. Launched by I-24 on November 22, 1942, 14 miles off Cape Esperance, it was never seen again. The fifth loss was I-16 tou, launched on November 28 from just 3,000 yards off Lunga Point. Sublieutenant Hiroshi Hoka and Petty Officer Shinsaku Inokuma managed a daring feat, firing through a screen of five destroyers to hit the 6,200 ton freighter USS Alchiba (AKA-6). The torpedo tore into the hold, igniting Alchiba’s cargo of aviation fuel, bombs, and ammunition. “The impact was followed immediately by an explosion throwing a column of flame and smoke approximately one hundred and fifty feet into the air. Fire immediately seemed to fill number two hold and to spread to number one hold” (Commanding Officer, USS Alchiba 1942). The crew managed to beach the burning ship at Lunga Point, where they hastily unloaded ammunition and fought the fire as small arms and ammunition overheated and exploded. The fire burned for days as the heroic crew of Alchiba, joined by volunteers from other ships, successfully fought to save the ship. After a month of resting half sunk as a “sitting duck,” Alchiba was refloated and moved to repair facilities (Tibbets 1996:49–50). Alchiba would live to fight another day, but I-16 tou and its crew did not return from the mission (Warner and Seno 1986:166).

On December 2, I-20 launched Lieutenant (j.g.) Chiaka Tanaka and Chief Petty Officer Mamoru Mitani. They attacked but missed the freighter SS Joseph Teal and then fled, pursued by depth charges. They nearly made it back to base but abandoned their craft and swam ashore. The attack was noted by Admiral Ugaki in his diary on December 3, who wrote that he had received a report that one of the midgets had “penetrated Lunga Roads and attacked an enemy transport between capes Lunga and Cori. After confirming two torpedoes [had] hit, it withdrew, submerging deep, and eventually came back to the base at Kamimbo, detouring Cape Esperance, after being attacked with depth charges for one and a half hours. Its crew was all safe, but the boat sank from leaking at 1430” (Chihaya 1991:292).

The seventh loss was crewed by Lieutenant (j.g.) Tomio Tsuji and Petty Officer First Class Daiseiki Tsubokura, who launched from I-24 on December 7. They torpedoed Alchiba, still stranded on the beach from the earlier attack, and flooded its engineering spaces. Two of the crew were killed and six injured, but as noted earlier, Alchiba survived (Commanding Officer, USS Alchiba 1942). The midget submarine crew did not. They were attacked by a SBD Dauntless dive bomber in an attack coordinated with PC-477 as they withdrew from Alchiba. The damaged sub and its crew sank in more than 2,000 feet of water. The last loss was on December 13, when I-16 launched Lieutenant (j.g.) Yoshimi Kado and Petty Officer Second Class Toshio Yahagi. They claimed to have engaged a destroyer before withdrawing and scuttling their sub near Kamimbo. Guadalcanal, like Diego Suarez, proved ultimately to be the finest hours for the kō-hyōteki corps, stirring feats of bravery and death at Pearl Harbor and Sydney notwithstanding. Two vessels had been damaged in each attack, although not taken out of the war. Ramillies, British Loyalty, Majaba, and Alchiba were all returned to service. The price was eight subs and six trained crew—and the gains purchased by their loss had no real effect. Despite their limited success, the midgets had failed to achieve even a tactical victory. The war had turned against Japan, which after Midway, now lost Guadalcanal.


Leave a Reply

Your email address will not be published. Required fields are marked *