The mere physicality of an edged-weapon encounter is dramatically different than that of a firefight. You will be up close, probably face to face with the bad guy. You will smell his breath, feel his sweat, see his face, and hear the groan when your knife is twisted out of his body. Putting a blade into someone's throat, twisting it, and then tugging it out is not a pretty sight.

Slashing attacks, while devastating in appearance, are usually superficial in nature and are not usually life threatening. Stabbing attacks, on the other hand, do not look bad on the surface, but the internal bleeding and damage can be extensive. Keep in mind that heavy clothing may provide protection from both slashing and thrusting attacks.

When using a thrusting attack, the blade should be twisted when withdrawing it for two reasons: to break the naturally occurring suction and to make a larger wound channel. The twist doesn't need to be a half turn, just a slight twist will do. Stab a piece of cardboard without twisting and then try again with a twist. You will see a much larger hole on the twisted one and the blade will come out easier.

Remember, the bad guy may not know he is being stabbed or cut. Most individuals who are attacked with an edged weapon say they thought they were being punched and had no idea that they were stabbed.

A while back, the History Channel interviewed a convicted felon who said he studied anatomy to discover the body's greatest vulnerabilities to an edged-weapon attack; you might consider following his lead.

Keep in mind that the body is a hydraulic system with 12 pints of blood, and it may take a 15- to 30-percent blood loss (two to four pints) to effect change in vital signs. Most of the areas will be familiar from your first-aid and CPR classes in which you learned the pressure points to stop bleeding.

Now, let's discuss where to attack a person with a knife.

Head and Shoulders

The head has multiple vital areas vulnerable to an edged-weapon attack. Horizontal slashes to the forehead will cause blood to flow into your opponent's eyes as long as he is standing up. Slashes to the eyes will result in loss of vision, thus reducing his ability to fight effectively. A hard thrust into the eyes may penetrate into the brain if the blade is long enough. Military training manuals detail a forceful attack into the ear canal with a slim, double-edged knife that may penetrate into the brain, as well.

Cuts to the neck and throat can cause rapid, high-volume blood loss. Deep horizontal slashes or multiple thrusts to the right side of the neck can sever the right common carotid artery or internal jugular vein. Cuts to the left side can sever the left common carotid artery. Be aware that both carotid arteries are well protected by several layers of muscle in the neck and are set deeper in the neck than the jugular. Creating an effective laceration in this area requires decisive force. Severing the carotid artery can cause unconsciousness, just like when using the carotid restraint. Thrusts or slashes to the front of the throat may damage the trachea (windpipe) or larynx (voicebox). Injuries to these areas are painful and will cause difficulty in breathing.

The subclavian arteries are located under the natural depression to the rear of the clavicle (collar bone) and in front of the trapezius muscle. These arteries supply blood to the arms and are not well protected by muscle. Plunging an edged weapon downward in this area may sever these arteries. A laceration in this area will cause rapid blood loss, and the pressure may cause a significant amount of blood to become airborne. Severing these arteries may cause unconsciousness in as little as 15 to 30 seconds if unchecked.

Arm Attacks

The muscles of the arms are smaller and demand less blood than most of the body. The inner arms and the outer arms have different types of skin on them. The outer skin is tougher while the inner arm skin is more delicate. There are very few visible blood vessels on the outside but several visible ones on the inside.

Your brachial artery runs under the bicep but is closest to the surface near the elbow. A forceful horizontal slash across the inner elbow may sever the brachial artery. Severing the brachial artery before the division into the radial and ulnar arteries will cause unconsciousness within 45 to 60 seconds, if the loss of blood is not slowed. A thrusting attack to the bicep and then a pulling/sawing motion toward the elbow may sever the artery and the distal bicep tendon. Injury to the distal bicep tendon will cause a loss of strength in the arm and reduce the ability to bend the elbow or twist the forearm.

Torso Targets

Injury to the heart will definitely diminish the ability of your attacker to fight effectively. But reaching the heart with an edged weapon may be harder than expected. It is protected by several layers of bone, muscle, and connective tissue. There have been many documented cases of knives becoming stuck between a person's  ribs, preventing the user from being able to  withdraw the weapon.

Thrusting into the heart is easiest using a double-edged knife with the blade held horizontally and aiming to the left of the target's sternum. One additional benefit of an attack to the heart is that you are likely to also injure the target's lung. A collapsed lung (pneumothorax) will diminish his ability to breath and in turn diminish his fighting ability. A tension pneumothorax (when air pressure builds up between the lung and the wall of the chest cavity) will slow or stop the return of blood to the heart from the veins. This will cause severe dysfunction of the cardiovascular system.

Injury to the kidneys will cause intense pain and rapid blood loss. The kidneys are located on both sides of the back, above the lumbar area, near the spine. They receive some protection from the lowermost ribs, but are painful if injured. Thrusting into the kidneys from behind while covering the mouth was taught as a silent enemy sentry killing technique in WWII.

Below the Waist

You are in the fight for your life, so forget that stuff about not hitting your opponent below the belt.

The pelvis area contains large blood vessels that supply blood to the legs, as well as the genitals. Thrusting attacks to the area where the inner thigh connects to the pelvis may sever the iliac arteries and veins. Slashing up or down in this area is also very effective. Cuts to the genitals are…well…cuts to the genitals. Enough said.

Then there's the big target in the legs: the femoral artery. This is the artery that supplies blood to the leg, and severing it will cause you to lose consciousness in as little as 15 to 30 seconds. The femoral artery is closest to the skin on the inside of the upper thigh. A vertical thrusting attack to the inner thigh can be very effective.

Horizontal slashing attacks above and below the knee can cause injury to the quadriceps (above knee) and patellar (below knee) tendons. Damage to these tendons will reduce overall leg strength, limit the ability to straighten the legs, and prevent the suspect from standing.

Finally, there are the feet. Edged weapon attacks on the feet can be very painful. The bones of the feet are delicate and numerous nerves are concentrated in this area. Attacks to the foot and tendons may be prevented by wearing high top shoes or boots. Vertical stabbing to the top of the foot will cause pain, but little blood loss. If the suspect is wearing low shoes or is barefoot, the Achilles tendon—the strongest and thickest tendon in the body—is easily accessible. Severing this tendon will prevent the suspect from standing on the toes, walking, running, or jumping.

This article is based on human anatomy and shows you how to disrupt some of the basic inner workings of that system. These techniques are brutal and may cause permanent damage, disfigurement, or death to your opponent. The potential results of your actions must be considered by the individual officer prior to using any of these techniques.

With all deadly force encounter training, use extreme caution when practicing the methods and techniques addressed in this article. Prior to implementing these techniques, check to make sure your local laws, department policies, and use-of-force protocols allow for such techniques. 

Douglas Iketani is a deputy sheriff with 18 years of law enforcement experience. A department use-of-force instructor, he is currently assigned to the Office of Homeland Security as a Technical Schools Instructor.