Class overview
Name	Type-A submarines
Builders	Kure Naval Arsenal Kawasaki Shipbuilding
Operators	Imperial Japanese Navy
Preceded by	Junsen Type
Succeeded by	Junsen Type B
Subclasses	Type-A (I-9-class) Type-A Modified 1 (I-12-class) Type-A Modified 2 (I-13-class)
Built	1938–1945
In commission	1941–1945

TheCruiser submarineType-A (巡潜甲型潜水艦,Junsen Kō-gata sensuikan) was a class of submarine in theImperial Japanese Navy (IJN), which served during theSecond World War. TheType-A submarines were built to take a role of the command ships for submarine squadrons. For this reason they had equipment for a headquarters, better radio facilities and a floatplane.

TheType-A submarines were divided into four classes:

• Type-A (甲型（伊九型）,Kō-gata,I-9-class)
• Type-A Mod.1 (甲型改一（伊十二型）,Kō-gata Kai-1,I-12-class)
• Type-A Mod.2 (甲型改二（伊十三型）,Kō-gata Kai-2,I-13-class)
• V21 Type (第5094号艦型,Dai-5094-Gō kan-gata,5094th vessel-class). The5094th vessel class boats were not built and remained only a design.

Project numberS35Ja. Their design was based on theJunsen III (I-7 class). Three boats were built in 1938-42 under theMaru 3 Programme (Boat # 35 - 36) andMaru 4 Programme (Boat # 138).

• Boats in class

Project numberS35B. Five boats were planned under theMaru Tsui Programme (Boat # 620 - 621) and theKai-Maru 5 Programme (Boat # 5091 - 5093). They were equipped with less powerful diesel engines which shortened the time needed to build them. Only one boat,I-12, was completed to the original design. TheI-13 and the later boats were converted to a new submarine class (I-13 class), because the number ofI-400 class boats was reduced.

• Boats in class

Project numberS35C. Four boats were planned under theMaru Tsui Programme (Boat # 621) and theKai-Maru 5 Programme (Boat # 5091 - 5093). However, four boats were converted to new submarine class (I-13 class), because a number of submarines of theI-400 class were cancelled. They had a large hangar and were equipped with bulges to be able to operate 2 × specialAichi M6A1Seiran attack bombers. The headquarters institutions were removed.

• Boats in class

Project numberS48. Three boats were planned under theKai-Maru 5 Programme. However, all boats were cancelled in late 1943, because the IJN turned its attention to the construction ofType E submarine [ja] (戊型潜水艦,Bo-gata sensuikan) in 1945.

• Boats in class

• "Rekishi Gunzō".,History of Pacific War Vol.17 "I-Gō Submarines",Gakken (Japan), January 1998,ISBN 4-05-601767-0
• Rekishi Gunzō,History of Pacific War Vol.63 "Documents of IJN submarines and USN submarines", Gakken (Japan), January 2008,ISBN 978-4-05-605004-2
• Rekishi Gunzō,History of Pacific War Extra, "Perfect guide, The submarines of the Imperial Japanese Forces", Gakken (Japan), March 2005,ISBN 4-05-603890-2
• Model Art Extra No.537,Drawings of Imperial Japanese Naval Vessels Part-3, Model Art Co. Ltd. (Japan), May 1999, Book code 08734-5
• The Maru Special,Japanese Naval Vessels No.13, "Japanese submarines I-13 class and I-400 class", Ushio Shobō (Japan), July 1977, Book code 8343-7
• The Maru Special,Japanese Naval Vessels No.31, "Japanese Submarines I", Ushio Shobō (Japan), September 1979, Book code 68343-31
• Senshi Sōsho Vol.88Naval armaments and war preparation (2), "And after the outbreak of war", Asagumo Simbun (Japan), October 1975

• Cruiser submarine

• Submarine classes
• Type A submarines
• Submarines of the Imperial Japanese Navy

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