Throughout World War II, the U.S bombings gradually degraded the Japanese munition manufacturing base.

Contrary to the Russians or Germans, the heavy armour threat was not very present, thus explaining the late development of the hollow charge.

The explosive was cast around the cone and covered by a cloth bag made of either silk or hemp twine.

[2] The upper extremity was made of a very basic impact firing mechanism, that detonated the grenade if it struck a hard surface at a speed of around 40 feet per second (12 m/s).

[2] A tail made from hemp strands served to stabilize the grenade in flight,[2] and ensured the target was struck successfully.