[3] The 20 cm naval rocket launcher was developed in the final stages of World War II by the Japanese Navy, as a low-cost, easy to produce weapon for use by naval troops as a last-ditch weapon for the defense of Japanese occupied islands.

Type 91 trinitroanisole explosive was poured into a lacquered shell body intended to stop the formation of picrate salts and the projectile was centrifugally armed by a nose fuze.

They were usually employed in groups of two or three covering landing beaches and although cheap and portable traverse and elevation were slow and the projectile range was short.

It has a barrel about 6 ft (1.8 m) long and was mounted on a steel split trail carriage with two spades.

When the desired angle was reached, the clamping handle at the left is rotated to lock the tube in position.