OK, let me clarify, stab wounds are much more difficult to treat medically than cuts. Without medical treatment both stab wounds and deep cuts will generally be fatal through massive blood loss or punctured organs (liver, kidneys, intestines, stomach, heart, sub-clavian artery, etc...). This was a big argument historically when the rapier became a prominent weapon, eschewing the cut for the thrust only. It was basically discovered (or decided) that a good thrust was more likely to kill a man by virtue of internal damage and infection (pre-antibiotics) while the cut had more stopping power (you can't use tendons and muscles when they're sliced open).
Of course literally you wouldn't be trying to block cuts and thrusts with your arms, but as I said if you want to grapple unarmed against a knifer you need your hands ready to attempt to control his wrist or block a cut/thrust to a vital area. Your left hand is prepared to go inside his wrist (assuming the knife is in his right hand) if he cuts or thrusts to your left side (the most natural motion for a right hander). Your right hand is held low (can be high) to cover his left hand or any attacks made to your right side. Your arms are retracted so they aren't targets he can slice up at will. By forcing him to attack your center of mass you are making it easier to to get inside or outside his wrist and control the weapon hand. I am not saying it's easy or that you'll have much success without being seriously injured, but the best defense you have is to minimize his effective targets and keep as much distance as you can. If he is smart he will back you into a corner and go to town.
I think we're all agreeing that a knife at close quarters is a fearsome weapon and you would be lucky to survive an encounter with an experienced knifer. Running is something you do when you have the room, you see the guy go for his knife, and you have a clear path to get away. Plasma has a good point, the instant you see him go for the knife you should go for the wrist to keep him from drawing it. IF you see him go for it, if he doesn't already have it in his hand. But running isn't just about being faster, it's about making escape your primary goal. Maybe he comes at you, you try to grapple and you get cut or stabbed, but you should be thinking about getting away as your best chance of surviving. What if he had a gun? What if you got shot once in the arm, wouldn't you try to get away still? Even if he could shoot you in the back? It's better than being shot in the front at point blank range.
Historical knife stances, I am working on getting some links together. The Medieval stuff is a little different since it is dagger-based and predicated somewhat on armored combat (big thrusting icepick/batons) but there is some good material there. The Renaissance and later covers actual knife fighting better, the Navaja lessons I took were the most glaring examples in my mind of the hand over the throat stance. Joachim Meyer's messer and dussak are good ones too. I promise some good examples by the end of today.
There are some good examples of the left hand position here in the dussack fighting of Joachim Meyer (dussacks are like really big knives or cutlasses). You will see several plates where the left hand is covering the throat. Loko at paltes F and M, the figures on the left are a good example. This is dueling for sure, both parties have a weapon, but the idea is similar. I also know that Meyer likes to change between a more Saber stance (left hand out of way as a target on hip) and a more knife or Messer stance (left hand by throat and ready to employ with a grapple).
I see it the other way around. If I run, I have a chance at being faster than the other guy, plus I´m terrified. If I try to fight him unarmed...well, from training I know that I have almost no chance (luckily, I´ve never been in a knife fight).
Originally Posted by Heffy