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It's a reasonably common trope for characters to use serrated axes, swords, scythes, or similar weapons. Aside from trying too hard to look cool, are there circumstances where a serrated blade would be more effective than a conventional blade?

Three main considerations come to mind, but I may be making false assumptions:

  1. A serrated edge will leave wider and more jagged wounds, causing additional pain, bleeding, and risk of infection.
  2. Serrations would be more difficult to manufacture.
  3. Serrations would be very difficult to sharpen.

I would expect this kind of blade to be ineffective against armor, but edged weapons generally aren't so hot under such circumstances anyway.

I'm thinking of forged weapons, not natural, though many animals have roughly serrated claws or bills, and teeth are more-or-less serrated by definition. Is this because it's difficult for a living thing to develop a very sharp edge like a human smith can with metal and a grindstone?

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I recommend having a double bladed weapon, so one edge serrated, and the other normal. Just in case... – XandarTheZenon Jan 15 at 14:32
Fighting creatures made of bread or wood – rogerdeuce Jan 15 at 17:15
Along the lines of your first consideration, my understanding is that a wound caused by a serrated weapon is likely to be more difficult to close, increasing the fatality rate. Even if the victim survives the fight, they may die afterwards. That is a benefit from a murderous perspective. – Dom Jan 15 at 18:49
Additionally, I'd like to add that serrations would get stuck in hair, clothes, etc very easily, actually impeding their ability to cut. – Hellreaver Jan 15 at 19:08
I'm pretty surprised noone mentioned blocking. When you use an edged weapon against an other edged weapon, half of the time you're blocking an attack. Now on a strait (as in "not serrated") weapon, the blade of the attacker can slice and get pretty close to those unprotected body areas, while on a serrated edge the blade will be held in place. A trained warrior can even benefit from this effect to disarm the oppone3. – mg30rg Jan 16 at 10:34

13 Answers 13

The Aztecs used Obsidian "Swords" which were effectively clubs with shards of sharpened obsidian embedded all down the sides to form a double-edged serrated blade. Given how sharp obsidian is, they made a very effective weapon! That said, like you have pointed out, such weapons are awful against armour — this is one of the things that led to the victory of the horribly outnumbered Conquistadores (that and smallpox).

The advantage here is that they could create a blade without having to use metallurgy (or indeed any knowledge of metal work) — the pieces of obsidian could be added individually without any forging process and could easily be replaced when a single "tooth" broke. Such a blade would be useful for someone who doesn't want to rely on the skills of a blacksmith to maintain or create a serviceable weapon.

P.S., technically, this doesn't meet your pre-requisite of "Forged", but I'm assuming from the context that you mean "man-made" as opposed to created using the forging process.

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You are quite correct, I really meant "man-made" as opposed to grown. Good point regarding the macuahuitl. Even if metalworking is an option, if there is some extraordinarily strong or sharp but difficult-to-machine material, sticking bits to a club may be worthwhile. In turn, this could become a cultural pattern which persists long after iron swords behind dominant. – user243 Jan 15 at 16:34
The Mesoamerican civilisations are a fantastic resource for "unusual" approaches to technology, because they had formed in a significantly different environment to Western Europe - the blades being a good example, the lack of a pack animal another. Because there was no "tainting" of ideas through communication with our ancestor civilisations, they seem to have developed completely different solutions to the same problems. Greece, Egypt, Rome etc. all borrowed from each other which negated the same effect in Europe. – I Stanley Jan 15 at 16:42

While this is slightly tangential to your question, a somewhat common real-world use of serrated edges on weapons is the back edge of many tactical / survival knives.

This serrated edge is not (generally) intended for combat, but rather to add functionality for non-combat uses - cutting wood for palisades, stakes, firewood; among other uses. While not necessarially more effective for combat, this does make the blade more effective as a tool.

This type of serrated back edge could also be usefull on something a bit bigger like a machete, designed as a tool for cutting through jungle, but perfectly servicable as a weapon.

To address your point about serrated vs straight edges on animals:

  • Many animals do evole fairly straight, sharp edges - see beaks.
  • Predatory animals have a slightly different use-case for their natural weapons then that which human weapons are designed for. Animals generally kill one thing, then eat it. This means that having your weapon (teeth / claws) get briefly stuck in your target is less dangerous then if you were a soldier on a battlefield. Serrated teeth are also better at cutting flesh when eating it.
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Very good points, thank you. One can imagine a society which uses serrated machete-like blades for cutting through tickets, and which retains the design in warfare because it's convenient or just because it's traditional. – user243 Jan 15 at 18:12

Pros - While Serrated blades are really hard to sharpen, but also very hard to dull, and having a chink knocked in it or a tooth knocked doesn't make the weapon any less threatening or dangerous. They're better against leather armor, cloth, rope and organics, like vines, wood and hide. They're better against straight-edged blades, which dull during impact swordplay, and depending on the style of serrations, could actually catch other blades.

Cons - Serrated blades can be more dangerous to the wielder simply because they're generally more dangerous. They require different sheaths than straight-edge blades. Once entering flesh or other organic material, they're hard to retrieve, so they're best if they're considered a consumable. This could be arrowheads, throwing daggers, one of many swords on hand, javelin points, et cetra

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I heavily doubt serrated blades will be more effective against leather and fibers. On the contrary, I would expect then to get tangled up easily, especially in rough fibrous materials like hemp. – Mike L. Jan 15 at 16:05
@MikeL. unless you have a strategy that revolves around hindering the opponent's limbs. Get the blade tangled in the sleeve and jank to pull the other guy off balance. – ratchet freak Jan 15 at 16:14
...leaving you disarmed. Not sure it's a good trade. – Charles Jan 15 at 22:32
@Charles Weapons designed to tangle in clothes were actually used. The use case was essentially non-lethal police work. Killing a drunken son of a powerful noble because he is disturbing the peace would have been pretty dangerous for a commoner paid to keep the peace. But they probably had had grips to keep sure you don't get disarmed. – Ville Niemi Jan 16 at 6:49
The question was, when serrated blades would be more effective, and in that instance, they are. It's like asking why anyone would need a staff with several pointed prongs on it outside of combat situations (because that's clearly something deadly)... then saying that response explaining pitchforks don't match the spirit of the question... That's exactly what the question was. – Vogie Jan 16 at 18:07

Most of the answers focus on sword or knife-like weapons, used to slash or stab. In those cases, a serrated blade does a lot of damage to skin; instead of a clean (or mostly clean) slice, a serrated blade would tear, rend, and shred any skin it passed by. If your sole goal is to make a ragged bleeding mess of anything you stabbed, and you are willing to take the extra cost of sharpening each serration, a serrated sword vs. a 'normal' sword probably wouldn't be much different, apart from the shape of the wounds caused.

However, more damage comes at a cost; stabbing someone with a thin, straight blade will take a lot less effort than stabbing someone with a serrated edge, doubly so if they are in any sort of armor. Even thick clothing would make a serrated edge less effective.

However, there are other uses for serrations; a special, very strong knife with (dull) serrations on one side, known as a sword-breaker, was used as an off-hand weapon, to catch and twist the sword of your attacker. These weapons could snap the blade of a sword that is caught by it. Occasionally serrated barbs were also added to shields, for much the same purpose.

Serrations on an axe or hammer may actually improve the weapon, though it would be easier to use a spike. The serrated edge would carry the force of the weapon strike through a much smaller surface area, possibly resulting in poking holes through the armor. Of course, sharpened serration would be quickly dulled, and prone to break off, which is why most hammers used a single sharp spike to pierce armor.

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A serrated blade will definitely cause much more damage than a straight blade. On a knife is one thing, but when you put this on a sword that you are using as your main weapon, the serration can actually be a deterrent.

All those serrations make it much more difficult to remove the blade once inserted. All those teeth are resisting removal and grabbing flesh and bone and armor and cloths. So once you stick someone you need to get the blade back out to fight the next person trying to remove your head. spending 5 minutes trying to get your weapon free is going to reduce your chances of survival.

Added: one justified use, might be some creature that has very tough skin and is difficult to kill. So you stick as many of the serrated blades into its body to kill it, if it pulls them out, it does even more damage to itself.

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Sawback Bayonet

The German army discontinued use of the sawback bayonet in 1917 after protests that the serrated blade caused unnecessarily severe wounds when used as a fixed bayonet.

The story goes that if anyone was captured with a serrated bayonet they would be killed on the spot, so they filed them down before going into combat.

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A soldier caught with a serrated bayonet wouldn't just be killed, he would be killed horribly. Probably the soldiers he was found with as well. If you had a serrated bayonet you had 0 chances of being taken prisoner, and 100% chances of dying, probably badly. – AndreiROM Jan 15 at 14:31
I couldn't find any specific references apart from that book which is officially fiction. Victors justice/history would probably hide the truth of it. For all that it's generally accepted to be so, I couldn't say as much without source. – Separatrix Jan 15 at 14:38
Serrated edges on utility knives, survival knives and even bayonets are common even today, with the understanding that even as far back as the American Civil War, only about 1% of battlefield wounds were caused by edged weapons. The reality is you are more likely to get killed with a serrated blade if you are the star of an ISIS video, rather than a soldier on a modern battlefield. – Thucydides Jan 15 at 20:33
So if possession of a serrated blade was considered such an evil thing that soldiers would be given no quarter if they had one, why did the AKM bayonet and M9 have them? – Random832 Jan 15 at 22:24

They could be used as weapons for intimidation that double as torture instruments. In this context, an evil soldier/secret policeman of some kind would press the serrated edge against a victim's face and then start rubbing it back and forth, or talking about doing it.

This would negate their ineffectiveness against armour - they're not intended for combat against somebody in full plate armour, but to scare people into obedience, which would exploit your first point.

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Does a flamberge count as serrated? Their blades were undulating which apparently had two applications; parrying an undulating blade causes vibrations in the parrying blade, slowing any counter attack. Secondly the flamberge was used to destroy halberds; the serrated blade was useful for dragging across the wooden shaft to saw through them.

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I wouldn't count that as serrated, personally, since it's a continuous cutting edge rather than cutting primarily with points. But it's certainly an interesting intermediate case. – user243 Jan 17 at 16:08

Realistically a continuous edge is better as weapon. Thus the starting point should be thinking about the drawbacks of a normal edge that a serrated edge doesn't have and under which circumstances they would be relevant.

Amount of metal

Before metal working people made weapons using microliths. This means attaching small pieces of stone worked to have a suitable edge to properly shaped piece of wood to form a weapon that is larger and more massive than can be directly made from the brittle stone and with sharper edge than wood can hold.

The stereotypical example is Aztec macautl, which used its large mass to make the edge effective in combat and allowed users to replace broken obsidian blades without replacing the whole weapon. This made sense since Aztecs didn't have a non-brittle material to make large weapons from. I expect they could have made copper maces, if they had wanted to, though.

So if your "cutting edge" material is expensive or brittle (or otherwise has limited endurance), you might want to use this construction and naturally end up with a serrated edge. Similar factors do apply to improvised weapons.

This is not sufficient to answer your question by itself, but should be added in as a factor to give some depth and historical background. Details like this make settings feel richer.

You don't need the weapon to be efficient

Armor penetration is not important if your expected opponents do not wear armor. Historically people had different weapons for use during wars against soldiers with armor and during peace against people wearing normal clothing. The latter category then further split to have different weapons to be carried for self-defense and for use in formal situations such as duels and sport.

So the first constraint would be that it probably isn't a military weapon. And more probably it isn't self-defense weapon either as such should be simple and efficient. A self-defense weapon that needs extra maintenance or fiddling so that you never quite keep it in top shape is a bad thing. That leaves formalized combat in duelling or sports. The line between the two is not always clear.

In such formalized combat leaving large messy cuts that are clearly visible to spectators, scar messily and hurt a lot would be beneficial. At the same time single hit kills or maiming is not really desired. A serrated edge can be built so that it cuts efficiently if messily to certain depth but then essentially becomes a blunt edge when cut depth exceeds the height of the teeth. Further you can easily cover the serrated edge with "antiseptic" material that ensures the cuts visibly scar and hurt enough to incapacitate recipient, but are unlikely to get infected.

This may seem unlikely, but the Aztecs mentioned earlier mostly warred to get captives to sacrifice to their god. Such wars were formalized enough for both sides to accept a less practical weapon that gets prisoners instead of casualties. Similarly Roman gladiators started as a religious ritual and gradually transformed to entertainment. They successfully used lots of "impractical" weapons. And not only was watching gladiators massively popular, people actually voluntarily participated in the training and even matches. In Germany they had an academic sport based on cutting each other in the face with a blade that makes shallow cuts. Such duelling scars were then a mark of honor to the bearer. A more full-body version could use a serrated blade.

In all cases you should include the historical connection to the microlithic weapon construction mentioned before to explain why this particular weapon is the proper traditional one that honors the gods and ancestors.

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Inuit used telluric iron to make knives by cold forging coin sized blades and attaching several of them to a bone handle so that they slightly overlap. So it has been done with metal not just obsidian and flint. – Ville Niemi Jan 17 at 15:30
+1 for stating different situations imply different weaponry. Outlandish weapons were largely ceremonial. Example: The Swiss Guard (the Pope's personal bodyguard) still carry halberds. – Tony Ennis Jan 17 at 17:00

In combat? Nothing, (though Bowls comment about causing damage from removing a weapon makes sense) there are no combat scenarios where a serrated blade is more useful than a non-serrated blade.

Serrations exist to give you more cutting edge so that you can keep an edge longer and were primarily developed for cutting wood.

To effectively use serrations in combat you would have to pull the weapon along your target. This would be completely useless against armor...even if that armor was wooden. Even against heavy fabric serrations would be less effective than a standard slashing blade (katana for example).

In short you would get more blade contacting the target using a standard edge when compared to a serrated edge.

Hold still I need to saw through your protective gear! -- unknown (He died)

Additional note: Having recently picked up forging as a hobby and having started on knives...I can tell you that the grinding/polishing/sharpening process is lengthy and time consuming.

Creating serrations would be even more difficult and the lack of benefit would lead to it being a style choice for the wealthy and not worth the time for mass produced army blades.

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Right, but against an opponent with bare skin or light cloth, no armor? – user243 Jan 15 at 16:58
The serrations still offer no improved combat effectiveness compared to a strait blade. – James Jan 15 at 16:59
You want to concentrate the force on as small an area as possible with a slash or thrust. A serrated blade distributes the force between multiple points, which is great for sawing, but not for thrusting or slashing. – Thucydides Jan 15 at 20:35
I suppose that if the serrations are sufficiently large and spikey, they would deal puncturing type wounds when the main weapon was swung. That's a bit more than serrated though. – Seeds Jan 15 at 21:31
A serrated edge on a curved weapon may offer some advantages, as a curved blade will slice along the attacked surface. On a straight edged weapon though, I'd agree, it would be of no benefit. – user1751825 Jan 17 at 3:45

Simple; more surface area on the blade. Minimum surface area when hit (increasing PSI), increasing surface area while "burying". Plus slice damage.

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Given this question already has nine other good answers, and a few of which had already gone into more detail on the ideas you suggest, you would do well to expand on your answer, either with more information on the science behind it, or perhaps some examples of designs that might be more or less effective, for example. You can edit your answer anytime. And, of course, Welcome to Worldbuilding SE! :-) – type_outcast Jan 16 at 12:16

Why does anyone use a serrated blade? I bought a serrated pocket knife for cutting up boxes and cutting paracord. For cardboard it lets you "saw" through the material.

I've seen serrated steak knives, not as cheap ever-sharp knives, but in a high quality design. The serrations are of a particular shape that have the effect of protecting the sharp part when it bottoms out on the hard plate, rather than mashing down the cutting edge.

So is any of this useful in combat? It might have to do with the type of defensive armor, uses of the blade other than against skin, and fighting techniques.

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I carried a serrated pocket knife for a while. Even though it was a CHinese knife of the lowest quality, it would cut anything. Finally the blade got loose in the handle and I retired it. My current pocketknife is not serrated - I didn't want to deal with sharpening it. – Tony Ennis Jan 18 at 23:09

This depends in part on what serrated really means. If we're talking about 'fantasy serrations' where the edge has enormous teeth,... I'll leave that to other posters. I'll add that knobs, fantasy spikes, protrusions, bumps, and similar doodads get hung on things.

As an alternative to fantasy serrations, consider "Damascus" steel. This is steel that is made by repeated folding and forging different metals until they weld and bond together. This gives an alloy that is intended to have positive attributes of the original metals. So, say we have a Damascus sword. When sharpened, you get a nice edge. Why not, at least one of the metals is iron. But the sword is still made of different metals and they will wear at different rates. The softer metals wears away during the final stropping. Now you have an edge that's serrated on the microscopic level. And this is the edge of legend. So against soft targets wearing cloth or leather, the sword is a meat saw - the serrations focus the energy of the blow and cause disproportionately severe wounds. And like a steak knife, the cuts are very clean. No energy is wasted. But against hard targets, the edge is retained due to the tougher steel. It is no wonder the ancients though such blades were magical.

To address your points:

  1. (leave wider and more jagged wounds...) Deeper but cleaner.
  2. (Serrations would be more difficult to manufacture) Yes, it takes a ton of know-how and effort to successfully create Damascus steel.
  3. Serrations would be very difficult to sharpen. No, normal sharpening would do.
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