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Type 4 20 cm Rocket launcher
Japanese Type 4 20 cm Rocket Mortar with a 20 cm shell.jpg
Type 4 20 cm Rocket Mortar at the Yasukuni Shrine
Type Rocket artillery
Place of origin  Empire of Japan
Service history
In service 1943-1945
Used by War flag of the Imperial Japanese Army.svgImperial Japanese Army
Wars World War II
Weight 227.6 kg (502 lb)
Barrel length 1.923 m (6 ft 4 in)

Shell 83.7 kg (185 lb)
Caliber 203 mm (8 in)
Elevation 40° to +65°
Traverse 300°
Muzzle velocity 175 m/s (570 ft/s)
Maximum range 2,400 m (2,600 yd)

The Type 4 20 cm Rocket Mortar (四式二十糎噴進 Yonshiki nijyū-senchi funshinhō?) was a 203 mm rocket mortar used by the Imperial Japanese Army in the final stages of World War II.

Development and design[]

The Type 4 rocket mortar was developed in the final stages of World War II by the Japanese Army Technical Bureau, as a low-cost, easy to produce weapon, which had an advantage of greater accuracy over conventional mortars in that it fired spin-stabilized projectiles. The first units were deployed in 1943, and were used successfully in combat during the Battle of Iwo Jima and Battle of Okinawa. Due to its ease of construction and portability, the Type 4 was produced in large numbers and distributed to hidden arsenals for use as last-ditch weapons during the projected Allied invasion of the Japanese home islands.

Although the weapon came with a standard mortar tube with tripod mounting, if necessary, the rocket-propelled round could be launched from an ordinary pipe or culvert with sufficient diameter, wooden rails, or even directly from a slope in the ground.[1]


  • Bishop, Chris (eds) The Encyclopedia of Weapons of World War II. Barnes & Nobel. 1998. ISBN 0-7607-1022-8
  • Chamberlain, Peter and Gander, Terry. Heavy Field Artillery. Macdonald and Jane's (1975). ISBN 0-356-08215-6
  • Chant, Chris. Artillery of World War II, Zenith Press, 2001, ISBN 0-7603-1172-2
  • McLean, Donald B. Japanese Artillery; Weapons and Tactics. Wickenburg, Ariz.: Normount Technical Publications 1973. ISBN 0-87947-157-3.
  • US Department of War, TM 30-480, Handbook on Japanese Military Forces, Louisiana State University Press, 1994. ISBN 0-8071-2013-8

External links[]


  1. [1] Taki's Imperial Japanese Army home page

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