By the time of World War 2 (1939-1945), many national powers had standardized on an anti-personnel fragmentation hand grenade. Originally, the Japanese military relied on the "Type 91" series of 1931 but this design found better use as a rifle-launched instrument over time. The Type 91 itself was intended as an improvement from earlier "Type 10" design of 1921. In 1937, an all-new, more effective design was unveiled as the "Type 97". This offering benefitted through use of a better TNT filling and a 4 to 5-second delay detonation mechanism. Like other hand grenades of the time, the Type 97 exhibited a cylindrical shape with a beveled grip pattern ("pineapple") and pull-pin safety feature. The operator was required to drive down the firing pin via threaded screw at the base of the striker to which the safety pin was then pulled. The grenade was activated by hitting it against a hard surface to allow the pin to strike the primer and begin the delay period. From this point forwards, the operator had a few seconds to throw the grenade at the intended target area.
In practice, the Type 97 was not a complete anti-personnel solution for it lacked the inherent "punch" when compared to contemporaries of the day - primarily British and American hand grenades it faced in the Asia-Pacific Theater. The fuse was not a wholly sound mechanism and proven to be generally unreliable (and in some instances quite dangerous for the operator). Nevertheless, it remained the standard-issue fragmentation hand grenade for Japanese Army and Marine forces for the period spanning 1937 to the end of the war in 1945 due to its widespread availability. It saw further service in the Soviet-Japanese Border War (1932-1945) as well as the Second Sino-Japanese War (1937-1945).
The Type 97 series was slightly improved in the upcoming "Type 99" model line which appeared in 1939 and was used until 1945. The Type 99 proved more versatile and did not require the operator to thread the firing pin into action. It became a standardized "rifle grenade" during the Second Sino-Japanese War and garnered the nickname of "Kiska Grenade" by the Allies.
Imperial Japan
