The Type 4 40cm rocket was developed in the final stages of World War II by the Imperial Japanese Army Technical Bureau, as a relatively low-cost, easy to produce weapon, which had an advantage of greater accuracy over conventional mortars in that it fired a spin-stabilized projectile.

Due to its ease of construction, it was produced in limited numbers and distributed to hidden arsenals for use as last-ditch weapons during the projected Allied invasion of the Japanese home islands.

[4] The Type 4 40cm rocket was restricted to launch via standardized fixed wooden troughs which were largely constructed by Japanese Army garrison toops, and not steel tubes like the Type 4 20cm rocket mortar.

During 1945 construction of the fixed wooden launchers outpaced actual production of the Type 4 40cm rocket.

Range of the Type 4 40cm rocket was controlled via variable bleeding of the propellant gases.