Type 4 20 cm rocket launcher

Type 4 20 cm rocket launcher
Type 4 20 cm rocket mortar. The baseplate is incorrectly positioned, extending backwards. It should face forward in order not to get damaged during firing.
Type	Rocket artillery
Place of origin	Empire of Japan
Service history
In service	1944–1945
Used by	see Users
Wars	World War II
Production history
Designed	1943
Produced	1944-1945
No. built	9,800 rockets and about 1,800 launchers
Specifications
Mass	227.6 kg (502 lb)
Barrel length	1.923 m (6 ft 4 in)
Shell	Total: 83.7 kg (185 lb) Explosive: 15.6 kg (34.4 lb) Propellant 8.4 kg (18.6 lb)
Caliber	203 mm (8 in)
Elevation	40° to +65°
Traverse	300°
Muzzle velocity	175 m/s (570 ft/s)
Maximum firing range	2,400 m (2,600 yd)

The Type 4 20 cm rocket mortar (四式二十糎噴進砲, Yonshiki nijū-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

During World War II there was considerable infighting between the Imperial Japanese Army and the Imperial Japanese Navy as both competed for scarce resources. A consequence of this competition is that each produced similar but different weapons. An example of this competition was the Army Type 4 20 cm rocket launcher and the 20 cm Naval Rocket Launcher.

The Type 4 20cm 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. The Type 4 20cm rocket used a double base solid-propellant whose exhaust gasses were forced through six venturis drilled in the base of the rocket which spin-stabilized the projectile. The rocket used trinitroanisole explosives and was nose fuzed. The fuzes were the same used on the Type 100 mortar round and could be either be set for instantaneous or time-delay action.

The first units were deployed in 1944, and were used successfully in combat during the Battle of Luzon, Battle of Iwo Jima, and the 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.

According to U.S. Army reports, Type 4 20cm rockets were captured by U.S. Army troops during the 1945 Battle of Luzon and were subsequently utilized to a limited degree against Japanese forces. The U.S. Army intelligence assessment of the system stated that the Type 4 20cm rocket mortar was a “simple, sturdy, mobile device, capable of fine adjustment for accurate fire.”

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.

Users

• Japan − Used by the Imperial Japanese Army
• United States − Limited use of captured rockets in the Battle of Luzon

Photo Gallery

• 
  A schematic of rocket components.
• 
  A Type 4 rocket launcher in the Yasukuni Shrine.
• 
  A Type 4 launcher opened for loading.
• 
  A Type 4 rocket on a launch ramp.

References

• 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.
• Ness, Leland (2014). Rikugun: Volume 2 - Weapons of the Imperial Japanese Army & Navy Ground Forces. Helion. ISBN 978-1-912174-58-4.
• US Department of War, TM 30-480, Handbook on Japanese Military Forces, Louisiana State University Press, 1994. ISBN 0-8071-2013-8

External links

• Type 4 on Taki's Imperial Japanese Army page