Type A Kō-hyōteki-class

Type A Kō-hyōteki-class. The Type A Kō-hyōteki-class was a class of Imperial Japanese Navy midget submarines used during the Pacific War. Designed for stealthy attacks on enemy anchorages, these two-man vessels were launched from larger submarines and saw their most famous deployment during the attack on Pearl Harbor. Despite their limited tactical successes, they represented a significant investment in special attack unit doctrine and influenced subsequent Japanese suicide weapon development.

Development and design

The development of the Type A Kō-hyōteki-class was spearheaded by the First Naval Technical Department at the Kure Naval Arsenal, with Captain Korechika Anami playing a key advisory role. The design prioritized minimal size and stealth for penetrating defended harbors, drawing conceptual inspiration from earlier Royal Navy X-class submarine experiments. Each vessel was powered by a single electric motor driving a single propeller, with electricity supplied by batteries stored beneath the decking. The primary armament consisted of two 450 mm Type 97 torpedoes, mounted externally in forward-facing tubes. Navigation and attack were conducted via a simple periscope, and the hull was constructed for a maximum test depth of approximately 100 meters. The program was highly secretive, with training conducted at a dedicated base on Ōurazaki peninsula near the Kamegakubi Naval Proving Ground.

Operational history

The operational debut of the Type A Kō-hyōteki-class occurred during the attack on Pearl Harbor on December 7 1941, where five vessels were launched from I-class submarines including the I-16 and I-18. One, commanded by Ensign Kazuo Sakamaki, became the first Japanese prisoner of war after washing ashore on Waimanalo. Subsequent deployments included an unsuccessful sortie against Sydney Harbour in May 1942, resulting in the Sydney Harbour raid, and attacks during the Battle of Madagascar at Diego-Suarez. They were also used in the Guadalcanal campaign, notably in a failed attempt to attack shipping in Ironbottom Sound. Later in the war, many were deployed for harbor defense around the Japanese archipelago, including at Okinawa and Yokosuka Naval District, often as static coastal artillery batteries or in planned kamikaze roles.

Specifications

The Type A Kō-hyōteki-class had a submerged displacement of 46 tons and measured 23.9 meters in length with a beam of 1.8 meters. Propulsion was provided by a 600 shaft horsepower electric motor, yielding a top speed of 23 knots submerged, though endurance was limited to roughly 55 nautical miles at 2 knots. The vessels operated with a crew of two: a pilot and a navigator/executive officer. Armament was strictly two 450 mm torpedoes. Operational range was entirely dependent on the endurance of the launch submarine, typically an I-class submarine or later a modified Type D transport submarine.

Variants

The basic Type A design led to several variants. The Type B was a slightly improved model with a wave-resistant conning tower and better habitability, used in the Attack on Sydney Harbour. The Type C variant was optimized for attacking anchored vessels, sometimes carrying a diver for attaching limpet mines. The most significant derivative was the Type D (Kōryū), a larger, mass-produced class intended for coastal defense, hundreds of which were constructed as the war situation deteriorated. Additionally, the Kairyū was a smaller, cheaper suicide torpedo boat developed from the midget submarine concept, and the secret Yamato-class battleships were once considered as potential launch platforms for these craft.

Surviving examples

Several Type A Kō-hyōteki-class hulls survive as museum pieces and war memorials. The most intact is the Ha-19, recovered after the attack on Pearl Harbor, which is displayed at the National Museum of the Pacific War in Fredericksburg, Texas. Another, recovered from Kiska in the Aleutian Islands Campaign, is exhibited at the USS Bowfin Submarine Museum & Park in Pearl Harbor. Wreckage from the submarines involved in the Sydney Harbour raid is held by the Australian War Memorial in Canberra, and a conning tower is displayed at the Japanese Naval Academy in Etajima. Additional relics, including a salvaged vessel, are part of the collection at the Yamato Museum in Kure.

Category:Midget submarine classes Category:Imperial Japanese Navy submarines Category:World War II submarines of Japan