Warships of the Imperial Japanese Navy: Midget Submarines and Submarine Tenders

Imperial Japanese Navy Midget submarines

This class includes the smallest of the Japanese submarines, from midget submarines to manned torpedoes often used for suicide attacks.

Kō-hyōteki Type A (甲標的, Target 'A') class of Japanese midget submarines had hull numbers but no names. For simplicity, they are most often referred to by the hull number of the mother submarine. Thus, the midget carried by I-16 was known as the I-16 midget. The midget submarine hull numbers beginning with the character "HA", which can only be seen on a builder's plate inside the hull. Fifty Ko-hyoteki were built. The "A Target" name was assigned as a ruse – if their design was prematurely discovered by Japan's foes, the Japanese Navy could insist that the vessels were battle practice targets. They were also called "tubes" and other slang names.

Kō-hyōteki-class submarine grounded after the Attack on Pearl Harbor, December 1941.

Kairyū Type (海龍, Sea Dragon) was a class of midget submarines designed in 1943–1944, and produced from the beginning of 1945. These submarines were meant to meet the invading American Naval forces upon their anticipated approach of Tokyo. Over 760 of these submarines were planned, and by Aug 1945, 250 had been manufactured, most of them at the Yokosuka shipyard. These submarines had a two-man crew and were fitted with an internal warhead for suicide missions.

Kaiten Type (回天) was a torpedo modified as a suicide weapon, and used by the Imperial Japanese Navy in the final stages of the Second World War. Kaiten means "return to the sky"; however, it is commonly translated as "turn toward heaven". Early designs allowed for the pilot to escape after the final acceleration towards the target, although whether this could have been done successfully is doubtful. There is no record of any pilot attempting to escape or intending to do so, and this provision was dropped from later production kaitens. Six models were designed, the types 1, 2, 4, 5 and 6 were based on the Long Lance type 93 torpedo (24 inch oxygen/kerosene), and the Type 10, based on the Type 92 torpedo (21 inch electric). Types 2, 4, 5, 6 and 10 were only manufactured as prototypes and never used in combat.

Kaiten manned torpedoes, stacked atop a departing submarine.

The Kaiten was a torpedo modified as a suicide weapon, and used by the Imperial Japanese Navy inthe final stages of the Second World War. Kaiten means "return to the sky"; however, it is commonly translated as "turn toward heaven".

Early designs allowed for the pilot to escape after the final acceleration towards the target, although whether this could have been done successfully is doubtful. There is no record of any pilot attempting to escape or intending to do so, and this provision was dropped from later production Kaitens.

Six models were designed, the types 1, 2, 4, 5 and 6 were based on the Long Lance type 93 torpedo (24 inch oxygen/kerosene), and the Type 10, based on the Type 92 torpedo (21 inch electric). Types 2, 4, 5, 6and 10 were only manufactured as prototypes and never used in combat.

US Navy Historical Center caption : "Japanese Type D ("Koryu") Midget Submarines In a drydock at Kure Naval Base, Japan, 19 October 1945. There are at least four different types of midget submarines in this group of about eighty-four boats, though the great majority are of the standard "Koryu" type. The two boats at right in the second row appear to have an enlarged conning tower and shortened hull superstructure. The two boats at left in that row are of the earlier Type A or Type C design, as are a few others further back in the group."

This class includes the smallest of the Japanese submarines, from midget submarines to manned torpedoes often used for suicide attacks.

(Library and Archives Canada Photo, MIKAN No. 3599747)

Canadian and American soldiers examine abandoned Imperial Japanese Navy Ko-hyoteki class midget submarines found at Kiska in the Aleutian Islands, Alaska, 1 Sep 1943.

(USN Photo)

A heavily damaged midget submarine base constructed by occupying Japanese forces on Kiska Island, photo taken sometime in 1943, after Allied forces retook the island.

(Author Photo)

Imperial Japanese Navy Ko-hyoteki class midget submarine used at Pearl Harbor on 7 Dec 1941.  National Museum of the Pacific War, Fredericksburg, Texas.

Type-C Japanese Midget Submarine War rests in front of The Pacific National Historical Park in Guam. It is the last Type-C Japanese midget submarine in existence.

The submarine was built in 1944 by Ourazaki at the Kure Naval Yard in Hiroshima prefecture. It was captured by the U.S. when it ran aground on Togcha Beach, near Ipan Talafofo, in August 1944, more than a week after the Battle of Guam ended. The Imperial Japanese sailors aboard held off American troops for three days before surrendering.After it was captured, the submarine was gutted and displayed at Camp Dealey on Toghca Bay. When Camp Dealey closed in 1952, the submarine was moved to Naval Base Guam. It was transferred to its current location in 2008.

The Imperial Japanese Navy developed the midget submarine (Kō-hyōteki in Japanese) in secret throughout the 1930s to counteract the strength of the U.S. Navy. Five midget submarines took part in the attack on Pearl Harbor. The original intent was to deploy the midget submarines in the path of enemy fleets but ultimately, they were used for harbor attacks and coastal defense. The Type-C midget submarine (Kō-hyōteki hei-gata in Japanese) was the second generation of midget submarine. Developed between 1942–1943, they were 81-feet long, weighed 49 tons, and were designed for a crew of three (two sailors and an engineer).

Unlike earlier Japanese midget submarines, Type-C subs were equipped with a 40hp/25kW diesel generator which could be used when running on the surface or to recharge the batteries. This allowed Type-C submarines to travel much further from their carrier than Type-A midget submarines. The Type-C midget submarines could travel up to 120 sea miles at four knots and had a top speed of nineteen knots when submerged. They were armed with two bow mounted 17.7-inch torpedoes. Crew accommodations were cramped; the only place sailors could stand upright was in the sub's control room. As many as forty-seven Type-C submarines were built, but only fifteen saw action during the war. Eight of them were sunk during battle. This is believed to be one of the seven not accounted for, and the only Type-C midget submarine still in existence. (National Park Service)

Kairyū-class submarine

(USN Photo)

Japanese "Kairyu" type midget submarines at the Yokosuka Naval Base, Japan, September 1945. Boats bearing numbers 4016 (at right) and 4018 (3rd from right) are training versions, with a second periscope mounted behind the main periscope's fairing, 1 Sep 1945.

The Kairyu-class of midget submarines were designed in 1943–1944, and produced from the beginning of 1945. These submarines were meant to meet the invading American Naval forces upon their anticipated approach of Tokyo. Over 760 of these submarines were planned, and by August 1945, 250 had been manufactured, most of them at the Yokosuka shipyard. These submarines had a two-man crew and were fitted with an internal warhead for suicide missions.

(At by At Photo)

Kairyu in the Yamato Museum, Japan.

(Yasuhiro Arakawa Photo)

Kairyu in the Yamato Museum, Japan.

(Official USN Photo, located at the US National Archives, 80-G-339841)

Japanese submarine under construction at Yokosuka Naval Base on 7 Sep 1945.

Submarine Tenders

Jingei-class

Submarine tender Jingei Chogei.

‍6,240 tonnes.

Taigei-class

Submarine tender Taigei.

‍16,700 tonnes. Later converted into a light aircraft carrier.