In mid-1944, with coastal defense requirements becoming urgent, the Japanese Navy developed an improved version of the Type A, B & C midget submarines. Designated "Type D" and nicknamed "Koryu", the new design was somewhat larger than the earlier types, featured a more powerful diesel engine and had improved operating endurance. The "Koryu" also had a five-man crew, two more than in the Type C, but the same armament of two 45cm (17.7") diameter torpedoes.
The Type D midgets displaced about 60 tons and were 86 feet long. Propelled by a 500 horsepower electric motor, maximum submerged speed was 16 knots. On the surface, with an 150 HP diesel charging the electric batteries, speed was 8 knots and range about 1000 nautical miles. As with the earlier types, individual boats had alpha-numeric names in the "HA" series.
The the first Type D boat, HA-77, was completed in January 1945. Some 115 units had been completed when Japan capitulated in August 1945. Nearly 500 more were under construction. Some of these submarines, intended for training pilots for "Kaiten" type manned torpedoes, had an enlarged conning tower and two periscopes.
This page features photographs and drawings of individual Japanese Type D ("Koryu" type) midget submarines, and provides links to additional views.
For additional images of Japanese Type D ("Koryu"
type) midget submarines, see:
If you want higher resolution reproductions than the digital images presented here, see: "How to Obtain Photographic Reproductions." |
Click on the small photograph to prompt a larger view of the same image.
Photo #: NH 78667 Japanese Midget Submarines: Type D ("Koryu") class -- at top and center -- and "Kairyu" class -- in lower left Sketch inboard profile plans, with hull section plans for the "Koryu" class. Copied from "Extracts from Small Battle Units of Foreign Powers, Appendix III: Japanese Midget Submarines and Explosive Motor Boats", page 38. U.S. Naval Historical Center Photograph. Online Image: 58KB; 740 x 500 pixels |
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Photo #: 80-G-339831 Japanese Type D ("Koryu") Midget Submarine On the ways at the Yokosuka Naval Base, Japan, 8 September 1945. Official U.S. Navy Photograph, now in the collections of the National Archives. Online Image: 131KB; 590 x 765 pixels Reproductions of this image may also be available through the National Archives photographic reproduction system. |
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Photo #: 80-G-339840 Japanese Type D ("Koryu") Midget Submarine On the ways at the Yokosuka Naval Base, Japan, 8 September 1945. Official U.S. Navy Photograph, now in the collections of the National Archives. Online Image: 134KB; 740 x 615 pixels Reproductions of this image may also be available through the National Archives photographic reproduction system. |
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Photo #: 80-G-339841 Japanese Type D ("Koryu") Midget Submarine On the ways at the Yokosuka Naval Base, Japan, 8 September 1945. This submarine's afterbody has not been attached. Official U.S. Navy Photograph, now in the collections of the National Archives. Online Image: 162KB; 740 x 615 pixels Reproductions of this image may also be available through the National Archives photographic reproduction system. |
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Photo #: 80-G-351877 Japanese Type D ("Koryu") Midget Submarine Midbody of an incomplete "Koryu" in the assembly factory at Kure Naval Base, Japan, 19 October 1945. Official U.S. Navy Photograph, now in the collections of the National Archives. Online Image: 115KB; 740 x 610 pixels Reproductions of this image may also be available through the National Archives photographic reproduction system. |
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For additional images of Japanese Type D ("Koryu"
type) midget submarines, see:
If you want higher resolution reproductions than the digital images presented here, see: "How to Obtain Photographic Reproductions." |
30 March 2000