Why did the Japanese make curved swords?
Why did they move from straight blades to curved blades?
I gotta admit I had an answer to this question before diving into the research for this video,
and I’ve pretty much changed my mind.
Let me know if you agree with me later.
The first swords in Japan were straight swords, or chokutō 直刀.
The design originated from China.
Around the 300s or 400s we started seeing the first curved swords,
though the majority of swords were still straight.
Now that first bendy sword was probably not what you think.
It’s called the warabiteto 蕨手刀, and it’s beautiful.
At first you’re like, wait it’s not curved at all, it looks pretty straight.
You fool, look at the handle.
The blade was straight, but the curve was all in the handle.
So when you hold it, the straight blade points a little backwards.
This type of sword was a totally Japanese design, not derived from China.
One point for the Japan lovers, and nationalists.
It was created by the Emishi people in the north, who fought on horseback.
The Emishi were separate from the Yamato people in the southwest.
The Yamato would grow up to become the modern Japanese.
The Yamato got their first look at the warabiteto through that age-old cultural outreach program
called war.
They liked what they saw and started making swords like it.
Over time, it evolved longer and thinner, with the curve moving to the blade too.
At around the 900s, we started seeing the first tachi 太刀, which looks a lot like
the Japanese swords that we’re used to.
This brings us to the question...what previous swords evolved into the tachi?
Some historians say, “Well just look at it, you daft muppet.
It obviously evolved like this.”
And they do have a point, even if it is rude.
It does look obvious.
This would mean that the Japanese sword was an original Japanese invention.
But there is another argument that yeah these two swords look the same,
but they’re very different in construction.
This one has the blade and hilt in one piece, but the tachi blade is separate from the hilt.
It has a tang that you insert into a hilt.
That looks a lot like the straight swords we saw before, where the original design came
from China.
So it could have evolved from the straight blade and they just curved it.
So who’s right?
Well, in my opinion that no one asked for, I’m leaning towards these guys.
But, you know, the answer may be both.
I’m sure blacksmiths knew about all the different types of swords before the tachi.
It’s not hard to believe that they used their combined knowledge to create the tachi.
Whatever the case, after the curved tachi, the Japanese had a fever, and the only prescription
was more curved swords.
Like high school jocks after graduation, straight swords dramatically lost popularity.
And the nerds...still didn’t have friends, so this analogy falls apart.
But from then on, Japan almost exclusively made curved swords.
So why did they make this switch?
There are a few possible reasons.
The main competing arguments are because curved swords are better when fighting on horseback,
or because of differential hardening.
This is where I’ve changed my mind.
Let’s look at the first argument.
To help us, I’ve invited some experts to debate the issue.
William Anker: Well, you see, the samurai at the time were mainly mounted warriors.
While on a horse, it’s easier to slash with a sword than to stab.
Since curved swords are better at slashing, they became more popular with samurai.
David Weeb: Riiight... there are some problems with this dumb argument.
The main one is that at the time, a samurai’s main weapon on horseback was not a sword,
but a bow.
They were mounted archers like the Mongols.
Swords were a backup weapon, and hard to use on horseback.
They were mainly used when the samurai was thrown off his horse.
It makes no sense that mounted warfare led to the curved sword, when swords were rarely
used while mounted.
W. Anker: Well just because swords were not the main weapon, doesn’t mean they were
used so rarely on horseback that it didn’t warrant a change.
Battles are chaotic.
Sometimes you run out of arrows, sometimes it’s better to just hack at someone
rather than waste an arrow.
The point is, the sword is there to use on horseback when you need it.
The fact that horse riding cultures in other parts of the world usually wielded curved
swords tells us that there is something about curved swords
that makes it beneficial to warriors on horseback.
D. Weeb: Okay that is a good point, but my counter-argument is that my opponent
is a nincompoop.
W. Anker: Wha-what?? I’m not a nincompoop.
Linfamy: Alright, let’s move on to the other argument
for why the Japanese switched to curved swords.
Because of differential hardening.
D. Weeb: I propose that the curve actually began as almost an accident.
Blacksmiths wanted to make swords harder to break.
When you’re making a sword, as I do between Reddit debates,
you may think that you should make the metal as hard as possible.
But hard doesn’t necessarily mean resilient.
Really hard metal can cut deeper, but is brittle and can break more easily.
Softer metal is less prone to breaking, but won’t cut as sharp.
What you really want is a blade that is both hard and soft.
They achieved this using a process called differential hardening.
Linfamy: Let me cut in real quick and describe differential hardening.
It’s a way to make sure the edge of the blade is hard and sharp,
but the body is softer and more resilient.
This is done by heating up the blade, then letting the edge cool down faster than the body.
When metal cools down faster, it becomes harder, because that’s how metals work.
This makes the edge harder than the body.
So how do you make the edge cool faster?
By covering the blade with clay.
The blacksmith would cover the body with a thick layer of clay,
and only apply a thin layer to the edge.
He would then heat up the entire blade, then dip the whole thing in a hot liquid, like water.
It looks really cool when you see it.
So if you start with a straight blade, what happens is that since the edge has less clay
insulation, it cools down faster and contracts.
As it contracts, it bends the blade downwards.
But as the body gradually cools, it also contracts and curves the blade back up.
Since the edge cools faster, it keeps a lot of its heat expansion and becomes longer than
the body, causing the blade to stay up at a more erect position.
D. Weeb: Exactly, and this erection was why they had curved swords.
Differential hardening.
I want to be clear that this was only the original reason
why they started using curved swords.
It was a side effect of differential hardening at first, but then the Japanese really leaned
into it and started controlling the curve,
because there are real advantages to curved blades.
So what do you say to that?
W. Anker: I’d say poppycock! D. Weeb: You’re a poppycock.
W. Anker: The problem with that hypothesis is that they had already used differential
hardening to make earlier swords, straight swords.
The tachi was not the first weapon to be treated with differential hardening.
They already knew about the bending and compensated for it with earlier straight blades.
Therefore, differential hardening was not the reason
the Japanese switched to curved swords.
It was because they fought on horseback.
D. Weeb: …
You son of a turtle!
W. Anker: Wha-wha-what?
So I used to think that differential hardening was the reason the Japanese switched to curved swords.
Probably because God-Emperor Karl Friday believed it.
Look, just because I wanna snort his ashes after he dies, to gain his historical powers,
doesn’t make me a fanboy okay?
However, he has backed off of his position a bit.
The fact that differential hardening was already used before the tachi is pretty strong evidence
against this argument.
Curved swords probably do have advantages on horseback, and that’s why the samurai
switched to them.
Let me know in the comments if you agree with this.
I don’t buy the argument that they’re better for slashing on horseback though, because
Japanese swords are not curved enough to make a big difference.
Something like this would be good for slashing.
But even slightly curved blades do have this advantage: edge alignment.
Now any person obsessed with swords will tell you that edge alignment is really really important,
even if all you said to them was, “Hi, how are you?”
What does it mean?
When you want to cut something with a sword, you have to align the edge of the blade perpendicularly
to the thing you’re hitting.
If you’re a little off that 90 degree angle, the sword would twist and cause you to hit
with the flat of the sword and that’s just embarrassing.
The beauty of a curved sword is that it tends to align for you
so that you hit at the right angle. Because um physics.
The tip of the blade trails behind the main body and stabilizes it.
It has something to do with inertia, and Albert Einstein probably.
I wanna give a shoutout to a blog called Gunbai: Ancient Japanese Warfare.
He has a lot of articles on Japanese military history if you’re into that.
Link in the description.
Alright, check this out for another sword video.
Okay we have a new emperor patron this week, Wisdom of the Orient Cat
who is probably a bakeneko.
We also have a new patron, mate102102.
Thanks so much you guys.
Alright I love you, and spread the knowledge.