What’s the difference between a long knife, a short sword, and a dagger?

From A Matter of Length
People often wonder when does x length of blade become y weapon. When does a knife become a sword become a greatsword?
Unfortunately, the taxonomy of weapons is difficult. People made whatever weapons they wanted, and then later other people came along to try to figure out just what category the weapons fit into.
However, I can off some general guidelines, based on historical European usage, and some of my own opinion. But do remember, these lengths are not absolute, but relative to the user, and you can always find exceptions.
So, when does X become Y? To my mind, it has much more to do with how a blade is used than anything else.

Knives & Daggers
Firstly, a knife is any shortish blade. It can be double or single edged. All daggers are knives, but not all knives are daggers. a dagger is specifically a type of fighting knife meant for stabbing or thrusting, with less ability to cut. It will have a defined point, and often but not always two edges. Daggers typically feature a guard of some sort. Knives may not.
These are rondel daggers.

The name comes from the rondels or rounds at both ends of the grip. Rondel daggers were typically but not always optimized for penetrating the gaps in armor. You can see the bottom one is highly optimized with a strong, narrow blade. Sometimes they even had triangular cross sections. The middle one is a more balanced design, with two cutting edges and a reinforced spine.
This is a baselard, another kind of dagger.

It has the classic double-edge, inline point design that most people think of when they think of daggers.
This is a kabar.

It is both a fighting knife and a field knife, but it is not a dagger. It is a style of bowie knife. It has a single edged blade with a clipped point. It is a more balanced design, able to cut and thrust, but will not thrust as well as a dagger.
This is a kukri.

It is a fighting knife optimized for
cutting
. It does not thrust well.
This is a carving knife.

It has a single-edged blade and an in-line tip, but it is not intended for fighting. It lacks a guard and the blade is typically not robust enough to fight with reliably.
In European martial arts, at least those studied in HEMA, knives and daggers are mostly used in a reverse grip.

Due to issues of balance, weight, and human body mechanics, swords cannot be used effectively in a reverse grip, as a general rule. There are weird exceptions, but they don’t matter for this.
Therefore, I believe a dagger/knife becomes a sword when it becomes too long to use in a reverse (ice pick) grip. A knife is short enough that you can revers grip it for close fighting, such as the methods taught in 14th century German manuals. A sword is too long and becomes cumbersome when used this way.
Where is that line drawn? It depends on the user. I have observed and tested, that the demarcation point is a blade approximately as long as your forearm.

Note, that is from your wrist to the
outside
of of your elbow, not inside. This yields a typical length of about 9 to 14 inches.
The distance between my wrist and elbow is apx 12 inches, so the longest blade that I can use like a knife/dagger is about 14 inches. Longer than that and I change technique and start using it forehand, like a very short sword. If you have longer or shorter arms, that will change the length for you.

If I were to distinguish between a long knife and a short knife, I would say that a blade longer than your hand is a long knife, and shorter is a short knife.
Shortswords
So a blade longer than 12ish inches, depending on the particular user, is a sword. But why distinguish shortswords? Isn’t that just a D&D thing?
Well…not exactly. Certainly there were fairly short swords, such as messers,

or katzbalgers,

or even cutlasses.

But what makes these “short”?
It is my opinion that the useful distinction is that a shortsword is more easily used in close quarters. That is, as
Don Church
describes in
Das Messer
, shortswords combine the limb-hewing lethality with the close contact and grappling of dagger fighting. Further, I opine that shortswords are more easily used in tight quarters such as indoors.
But just how long can a shortsword be? I know of no definitive historical definition, but I’ve tested a number of blade lengths, and I believe the upper limit can be determined for a particular person thus.
Hold the sword in your normal grip. Hold the sword along the side of your leg, pointing straight down. The tip should not touch the floor. That is your upper limit.

For myself, this means that a blade between 14 inches (fewer is a dagger) and 27 inches is a shortsword.

Original question- What’s the difference between a long knife, a short sword, and a dagger?

Wanbasion Black Stainless Steel Knife Set, Sharp Kitchen Knife

Reply