| Type 4 20 cm rocket launcher | |
| Origin: | Empire of Japan |
| Type: | Rocket artillery |
| Is Ranged: | yes |
| Is Artillery: | yes |
| Service: | 1944–1945[1] |
| Used By: | Imperial Japanese Army |
| Wars: | World War II |
| Design Date: | 1943 |
| Production Date: | 1944-1945[2] |
| Number: | 9,800 rockets and 1,800 launchers[3] |
| Weight: | 227.6kg (501.8lb) |
| Part Length: | 1.923abbr=onNaNabbr=on |
| Cartridge: | Total: 83.7kg (184.5lb) Explosive: 34.4abbr=onNaNabbr=on Propellant 18.6abbr=onNaNabbr=on |
| Caliber: | 203abbr=onNaNabbr=on |
| Velocity: | 175m/s |
| Max Range: | 2400m (7,900feet) |
| Elevation: | 40° to +65° |
| Traverse: | 300° |
The was a 203 mm rocket mortar used by the Imperial Japanese Army in the final stages of World War II.
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.[4]
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 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.” [5]
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.[6]