Originally developed in 1928, the Type 89 Mortar was a mainstay of Imperial Japanese forces through World War II. Lightweight, compact, and easily transportable by a single operator, the Type 89 was nicknamed the "Knee Mortar" by Allied troops due to an unfortunate misunderstanding of the design of the baseplate. Intended for use with a downed tree or similar rugged material, the smooth curvature made it a good fit for a human thigh or knee; any American attempting to use their leg as a firing platform was destined for a painful lesson in Newtonian physics (specifically regarding equal and opposite reactions) and a trip to a field hospital. Designed to be fired at a fixed angle, range control is accomplished via a threaded bolt assembly that extends through the breech, effectively reducing the barrel length as needed. A double-action style firing mechanism is integrated into the bolt, and a spring loaded canvas cover protects the bolt slot. Matching numbers are present overall.