The Type 4 70 mm AT Rocket Launcher was a Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

ese rocket launcher

Shoulder-launched missile weapon

A shoulder-fired missile, shoulder-launched missile or man-portable missile is a projectile fired at a target, small enough to be carried by a single person, and fired while held on one's shoulder...

 used during the last year of World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. It was to be used in the Japanese mainland in case of an invasion by the Allies

Allies of World War II

The Allies of World War II were the countries that opposed the Axis powers during the Second World War . Former Axis states contributing to the Allied victory are not considered Allied states...

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It is comparable to the German Panzerschreck

Panzerschreck

Panzerschreck was the popular name for the Raketenpanzerbüchse , an 88 mm calibre reusable anti-tank rocket launcher developed by Nazi Germany in World War II. Another popular nickname was Ofenrohr ....

 and the American Bazooka

Bazooka

Bazooka is the common name for a man-portable recoilless rocket antitank weapon, widely fielded by the U.S. Army. Also referred to as the "Stovepipe", the innovative bazooka was amongst the first-generation of rocket propelled anti-tank weapons used in infantry combat...

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History

By 1944 the Americans were using M1 Bazooka anti tank rocket launchers in the Pacific Theater against the Japanese. Japanese military commanders decided that they needed a similar weapon. In 1944 they adopted the Type 4 70mm rocket launcher. Unlike the US rocket that used fins to stabilize it in flight, the Japanese rocket had angled venturis in the base to spin the rocket for stability. The 20 cm (8”) HE rocket used by the Japanese was also spin-stabilized so they were familiar with the production of this type of rocket.

Development

The launcher was made in two parts that were joined in the middle, similar to the US 3.5” Rocket Launcher. It was designed to be fired by a soldier while prone. The weapon itself had a bipod similar to the one on the Type 99 LMG (Light Machine Gun). The gunner lay with his body at approximately a 45 degree angle to the bore on the left side while the loader was similarly positioned on the other side. The pistol grip and trigger mechanism were attached to the rear half of the launcher. A cable ran from the trigger to the rear of the launcher where the hammer was located. The hammer and firing pin was mounted on an arm that looks like a mouse trap mechanism. The arm was above the bore and out of the way of loading the rocket when it was in the cocked position. Pulling the trigger pulled the pin holding the arm in position and the arm swung around under spring pressure, striking the primer and igniting the rocket.

The 70mm rocket, like the 20 cm model, used a mortar fuze. There would be no set back when the rocket was fired to arm an artillery fuze. The Japanese mortar fuse for the 81mm and 90mm used a simple shear wire to make it bore safe. The wire went through the brass body and aluminum firing pin plunger. Upon impact the plunger was forced back, shearing the wire and freeing the plunger to strike the firing pin and detonate the round. This system would work well with a rocket and was already available in the Japanese supply system.