On Killing by LtCol Dave Grossman, 2009, Excerpts
As we bring the physical distance spectrum down to its culminations point we must recognize that killing with a knife is significantly more difficult than killing with the bayonet affixed to the end of a rifle. Many knife kills appear to be of the commando nature, in which someone slips up on a victim and kills him from behind. These kills, like all kills from behind, are less traumatic than a kill from the front, since the face and all its messages and contortions are not seen. But what is felt are the bucking and shuddering of the victim’s body and the warm sticky blood gushing out, and what is heard is the final breath hissing out. Narratives of incidents in which individuals used a knife in modern combat are extremely rare, and knife kills other than the silencing of sentries from behind are almost unheard of.
The US Army, along with armies in many other nations, trains its Rangers and Green Berets to execute a knife kill from the rear by plunging the knife through the lower back and into the kidney. Such a blow is so remarkably painful that its effect is to completely paralyze the victim as he quickly dies, resulting in an extremely silent kill.
This kidney strike is contrary to the natural inclination of most soldiers, who would prefer to slit the throat while holding a hand over the victim’s mouth. This option has far less potential for silence, since an improperly slit throat is capable of making considerable noise and holding a hand over someone’s mouth is not always an easy thing to do. The victim also has the capacity to bite.