Japanese Type 89 “Knee Mortar”
The Type 89 “Knee Mortar” was one of the more unorthodox weapons of WWII, but nevertheless a lethal addition to Imperial Japan’s wartime arsenal. Part mortar and part grenade launcher, the Hachikyū-Shiki jū-tekidantō was patterned after similar devices of the period. This unconventional delivery system consisted of a long rifled tube mounted atop a curved butt plate (giving the appearance that one could brace the weapon against a bent knee). While the weapon could be fired by an individual soldier, it was more often handled by a pair of men, who typically steadied the launcher against a nearby tree stump or rock.
The Japanese recognized the inherent value of hand grenades during the late 1920s, but were unsatisfied with the relatively short range of the weapons. The “knee mortar” was intended to be held at a 45-degree angle, thus propelling a specially-designed 50 mm explosive in a high arc, reaching distances of over 700 yards. Ammunition types included HE (high explosive), fragmentation, smoke, and incendiary shells. The knee mortar proved particularly effective in the jungles of the Southern Pacific, where it claimed thousands of Chinese and Allied lives over the course of the war.
Coincidentally, the Type 89 could not, in all reality, be safely fired from the knee. While instances of the weapon being used as a direct-fire weapon were reported, a heavy recoil dictated that the device be braced against a solid object, such as a wall or tree.
In his book, Infantry Mortars of World War II, author John Norris recounts the fact that several soldiers and Marines suffered bruised thighs or broken femurs from firing the Type 89 off a cocked knee. Despite this, the “knee mortar” was still a devastating weapon that sent enemy troops diving for cover at the sound of its distinctive and foreboding “pop.”