Cut and thrust: the mechanics of the sword [Guest Post]

Cut and Thrust European Swords and Swordsmanship - Martin J. DoughertyBy: Martin J. Dougherty.

There are many possible weapons that can be put in the hand of a warrior. Some are better suited to certain tasks than others, yet all of them are designed to do the same thing – to incapacitate or kill an opponent.

In an environment where armed combat was a life-or-death matter, lethality was actually not always the foremost concern of the weapon designer. What was critically important was the ability to incapacitate an opponent without being hit by a return blow. Death was a secondary concern; what mattered was putting the opponent out of the fight. If he fell to the ground and stayed there for the duration of a battle, that was a better result than an opponent who struck a few more blows and then fell.

The lethality of the sword as a weapon, and its unsuitability to ‘less lethal’ situations, is mainly due to the mechanisms by which weapons cause harm. There are four broadly defined mechanisms; three of them cause the target’s skin to be broken by a sharp blade or point. This will, at the very least, cause bleeding and the risk of infection, and may cause trauma to muscles and other tissues that will never properly heal without surgery – assuming of course that the target is not killed by his injuries.

The fourth mechanism, blunt force, can sometimes be used to inflict a knockout blow by striking the head. However, a slight misjudgement can result in the blow either failing to do more than annoy the target, or causing a skull fracture and probably death. Blows to other parts of the body, such as the legs or shoulder area, with a blunt implement like a baton or the flat of a sword can subdue the target through pain and muscle trauma. However, this can take several blows and still risks inflicting an unintentional but nevertheless serious injury.

The mechanisms by which weapons cause harm can be loosely defined as:

  • Impaling
  • Slashing
  • Hacking
  • Impact

These mechanisms are defined by the concepts of force, impact and pressure, all of which are interrelated. The weight of a moving weapon, and how fast it is travelling, defines the amount of kinetic energy it has. When it strikes home, this energy is transferred to the target and may cause tissues, bone and the like to deform.

When force is concentrated at a sharp point, the amount of pressure exerted is greatly increased. This is why it is possible to push a drawing pin into a wall with your thumb, provided it is the right way round. An amount of force that can drive a pin into the wall would penetrate flesh easily, but if it is spread out over a large area then it cannot do so.

A point or edge on a weapon concentrates force in this manner. The moving mass of the weapon defines how much force it can deliver, and the sharpness of the point or edge translates that into pressure at a given spot. Pressure allows the weapon to punch deep into flesh with relative ease, seeking internal organs that can be punctured. The torso is especially vulnerable to such stabbing wounds; a penetration of just 5 cm can find a vital organ or artery, and 15 cm of penetration is likely to, especially in the chest cavity.

What, then, of the edge? The edge of a weapon can be considered much like an infinite series of sharp points, and can cause injury in two primary ways. If the weapon is swung hard, much like a blunt instrument, then the effects of its impact will be magnified by the sharp edge, which concentrates the force of the weapon into extreme pressure along the line of impact. A ‘hacking’ (also termed ‘shearing’ or ‘percussive’) blow of this sort will bite deep into flesh, benefiting from both the heavy impact and the sharp edge.

A lighter blade, lacking the mass to deliver a powerful blow, will not penetrate very deeply if used in this manner. It will rapidly be brought to a stop by the resilience of the target’s flesh. In order to cause serious injury, the weapon must move in contact with flesh, using a slicing motion to cause the blade to cut. A longer blade allows a deeper cut, as the blade slices the whole time it is moving in contact with the target. ‘Slashing’ blows of this type are delivered with the intent of making the blade slide across flesh rather than smashing into it.

Most edged weapons use a combination of slashing and hacking. An axe can be considered a pure hacking weapon, more or less, as its design is totally focused on delivering maximum force behind a sharp edge, punching the blade into flesh rather than slicing it open.

Swords, on the other hand, tend to be able to both hack and slash, sometimes in the same blow. An unskilled user will tend to deliver a hacking blow no matter what the weapon is designed for, and this may not be all that effective. A more skilled swordsman learns to push or draw a cut, using the impact of the weapon to bite into flesh and then drawing as much blade as possible through the wound to deepen and lengthen it.

As a general rule, the sharper a weapon is, the less kinetic energy it needs to cause damage; a very sharp point or edge can kill or disable an opponent with little effort, whereas a blunt weapon requires either more mass or more force, or both. It is not a coincidence that the sword-making art has produced weapons capable of taking and holding a sharp edge or point rather than nicely shaped but blunt metal clubs.

Martin J. DoughertyReproduced from Cut And Thrust: European Swords and Swordsmanship by Martin J Dougherty.

Martin J. Dougherty is a prolific historical and technical author, fencing coach, and the current president of the British Federation of Historical swordplay.