“Most importantly, the Knee Mortar needs a direct fire option while deployed, it was historically infamous for being used as a suppressive grenade launcher just as much as it was a field mortar. It was to a point the IJA had dedicated Knee Mortar teams take the role of LMG teams suppressing US positions with barrages of direct fire from their mortars”.
The Type 89 grenade launcher is the same as other mortars and is placed on the ground. It cannot be used on the knee, as strong recoil can shake and break the thighs.
To ppl afraid: it cannot be used on the move… as it cannot be used standing really either. It’s a “knee” mortar in name only, soldiers have to set the tube on the ground.