u/GunsenHistory

Based on several interactions I had over the years, I wanted to share a bit of a rambling post on Japanese swords, and their use in historical battles.

This topic was brought up again in a recent Matt Easton video. As for the subject of the video, which discussed which swords will be useless against plate armor, and to some extent armor in general, I find the choice of including "all Japanese swords" odd, and the arguments presented very lacking. The main reason for this post is to address once again the eternal, everlasting misconceptions people have on Japanese swords, their use and their durability.

Matt's argument rests on two main points. One, is the "material" issue. He claims Japanese swords are brittle at the edge, and soft at the spine which translates as the tip, and edges more likely to break off, and the sword to bend when used to attempt bypassing armor gaps. This implies that Japanese swords overall were unsuitable to sustain clashes with armor, or any other hard surface (including other swords).

This is a recurring idea that shows up systematically every time Japanese swords are discussed, despite the amount of literature, scientific and historical, to dismiss it.

The claim originates from the hardness level of Japanese swords. In material science, high hardness, in modern steel, correlates with brittle mode of failure. It also correlates with high strength, and low toughness. In layman terms, a very high hardness, high strength but low toughness material will resist to wear of the surface, localized plastic deformation, does require a lot of force (for a given cross section) to deform, and when it does it absorbs little energy and cracks (low elongation).

Now, the hardness value alone is not sufficient to prove all of the above, especially considering the pre-modern context of historical steels.

There are some interesting findings from a Japanese sword made 500 years ago. In the paper published by Kwak et al, they performed hardness, micro-tensile and micro fracture tests on two different antique swords. In the oldest of the two, they found that even with high hardness, the micromechanical testing study indicates that in the sharp-edge regions, strength and fracture toughness are simultaneously enhanced by the presence of fine pearlite.

Further, none of these settings are considering the effect of geometry. Edge geometry plays a fundamental role in terms of failure, and reinforced tips/edges with appleseed geometry are much more resilient against impact compared to finer ones. Here is a video showing impact testing on a modern, 1084 knife blade, hardened and tempered at 64HRc vs one hardened and tempered at 57 HRc-62 HRC. Using different practical impact tests, despite the anecdotal evidence, you can see that the harder edge performs much better than the softer one. And that is mostly governed by edge geometry and high strength, in fact at more acute edge angles, the aforementioned relationship is valid: the harder edge cracks while the softer one rolls.

As for the softer spine, we are again not considering the effect of geometry. Most Japanese swords, as a matter of fact, are very thick and rigid. Ignoring the fact that with pre-modern steel, you will not have a completely through hardened sword, and that most historical blades have ductile cores of wrought iron/low carbon steel, Japanese swords are much stiffer on average than many European blades such as rapiers or longsword designs. This alone should reframe the whole argument because no, Japanese swords are not easier to bend, quite the opposite, and when it happens they deform rather than break. I struggle to see how this can be a bad design for dealing with armor.

Finally, the second point rests on blade geometry and the shape of the tip. Ironically, in his video he is showing an elongated, slender tip geometry known as ōkissaki. With a regular, short Japanese style tip, I would agree that it will be very hard to successfully bypass mail. However, this is an entirely different geometry. We know some of those tips were reinforced, and the slender acute point definitely gives them a good chance to burst into mail rings. I think discarding their effectiveness without testing is not a great argument, especially since those tips were used against armor in various other contexts.

Overall, while Japanese swords did not transition into estocs, there was a change in blade designs from the 14th century which accounted for dealing with armor. Leaving aside the topic of the video, and extending the context as a general "swords use against armor", there is a text known as Kenpō Ryakki which talks about fighting in armor with swords.

It talks about striking with full force with a sword against hands and limbs to break bones. In a Chinese text written by Chen Zongyou, Exposition of the Original Shaolin Staff Method, it is written that

>Japanese swords, and the tie bian, they are the same

the tie bian being a mace. And the main strategy suggested is to aim for the gap and to thrust with your blade. That is also found in other later period manuals; from the Kōdōkan Jūdō Official Bulletin "Yūkō no Katsudō," Volume 6, Number 6: Jūdō Anecdotes from the Atsukaishin-ryū, based on the Noda Family Documents, we can read that:

>When the body is firmly protected by armor, it cannot be cut, so thrusting is preferable.

Most of the gaps identified in the Japanese armor system are also quite universal: the armpit, the face, through the gap in the skirt armor to the lower abdomen, the feet, the hands.

Some of these places, such as the groin and the armpit, could be shielded by mail patches, and other flexible armor elements. The tip of these swords was in a sense expected to deal with such armor. There is definitely a correlation between extension of flexible armor to cover the gaps, and ōkissaki/shobu zukuri geometries.

To conclude, I do not think that Japanese katana and Japanese swords in general are completely useless against heavy armor. The arguments on steel durability are exaggerated and overly emphasised on Japanese swords, while the development of dedicated geometries is often ignored.

For this post, I wanted to compile a brief essay on a highly misunderstood item: the so-called Nanban dō gusoku (南蛮胴具足), or European-inspired Japanese armour. This is defined as an armour featuring a peascod cuirass, with a prominent median ridge, often paired with a European morion or cabasette. Most importantly, these armours showcased a hybrid process in which the foreign European elements were integrated with Japanese ones, usually in the limbs' defence and in fittings of the helmet bowl and cuirass.

The major misconceptions around these items are twofold: their role in shaping Japanese armour development, and their popularity as extremely important, sought after item.

The first contact between European traders and Japan happened in 1543, and already by 1548, we read of the first military description by Nicolao Lancillotto. However, a proper trading relationship only started after the 1550s.

These trades were first and foremost about fungible goods, for the European to get Japanese silver and for the Japanese to bypass the Chinese ban following the Ningbo incident. The Europeans acted as middlemen to bring back an inflow of mainland Asian commodities.

Later in the final years of the 16th century and early 17th century, with the proper establishment of Luzon, Japan (Nagasaki in particular) played a role in being a supplier of various resources, including iron, flour, even weapons (!) and gunpowder.

The second purpose of these trading relationships was a religious one, as the Jesuits sought to expand their influence and spread Christianity. In this whole picture, trading of European weapons and in particular, armour, was extremely limited, a niche figure of exotic trade, and most importantly, it went both ways.

While the first Portuguese traders are famous for introducing modern firearms in Japan in 1543, the design was fully replicated in a few years and quickly spread across the country. In fact, according to Takehisa Udagawa, it was not only the Portuguese, but South East Asian pirates contributed as much, if not more, to the spread of gunpowder weapons. There was also an interest by some warlords to obtain modern Western artillery, which remained throughout the century.

When it comes to armour, there is little to no record outside of diplomatic gifts. Before the return of the Tenshō embassy in 1591, there is only one recorded instance of European armour being gifted to the Japanese, in 1554, and that was most likely a brigandine and a helmet. There is some research being done on the influence of European styles of helmets on the development of particular styles, but the results are still uncertain. The most famous Nanban gusokut that are reliably datable come from the year 1600 and are all associated with the Tokugawa household.

What we know about Japanese armour development is that solid, rigid clamshell types of cuirasses emerged in the Eastern part of the country, around the 1570s. This incidentally is also the region with the least amount of contact with European traders before the end of the 1590s. Therefore, a claim that is often made about European armours in Japan being pivotal in the development of native form of plate armours, is quite hard to support. There is no reliable evidence that these cuirasses were traded en mass, and most importantly, the Japanese styles of plate cuirass feature a very distinctive design.

A common myth is that both Uesugi Kenshin and Oda Nobunaga had a Nanban dō, the latter often depicted with a Western-style cape and a Nanban kabuto as well, but both of these depictions are fabrications of modern media rather than being grounded in history.

So, what do we know about these suits? There are four Nanban gusoku that can be traced back to the Tokugawa family, all made around the year 1600. One of Tokugawa Ieyasu himself, Sakakibara Yasumasa, Watanabe Moritsuna and Minagawa Hiroteru.

They all feature combined elements of Japanese armour, and were either made of imported European helmets or cuirasses such as the one of Ieyasu, or made locally such as the one of Sakakibara. In fact, a rather unknown fact about Nanban gusoku is that they were most of the time made in Japan. By the 1600, Japanese armorers had already developed a back and breastplate cuirass system, following-up on the eastern styles of armours which had a set of four hinges. Therefore, it became possible to have a hybrid process in which these European cuirasses could function as Japanese one.

The key to understanding Nanban gusoku is to see it through the Japanese perspective. It was adopted into the Japanese system as it featured many similarities and could be easily modified to suit other Japanese preferences. In fact, it happened with Ming Chinese and Korean Joseon helmets, which were also integrated into Japanese helmet with a Japanese style shikoro.

Were these suits popular? Definitely not. Even among the Tokugawa household, while it said that Ieyasu might have used that suit at the crucial battle of Sekigahara (there are two armours which are said to have been used by him), the family armour style transmitted through the future generations is entirely different.
Moreover, in 1616 Father João Roiz wrote:

>O presente que esta trouxe as cousas Ca pouco aceitas, porque os corpos de armas que trouxe, guadameçis, panos de armas, vidrios e hums relojos, pouco o nada servem em Japão, e para presente que immediatamente vinha de el rei foi cousa muito pouca, por lo que parece que ate agora teve tão ruim despacho, como sabemos. Alem de que os hereges dizem, e fazem Ca estas cousas sospeitosas e que são para outros intentos, como já em riba apontei [...].

Translated: The gifts that he brought were poorly received here, because the items he brought, body armour, embossed leatherwork, heraldic tapestries, glassware, and some clocks, are of little or no use in Japan. For a gift coming directly from the king, it was a very meager offering, which is apparently why he has received such an unfavorable reception, as we are aware. On top of that, the heretics are casting suspicion on these matters here, claiming they are intended for other purposes, as I have already noted above.

So even within the diplomatic gifts, it does not seem that these items received popular attention as it is often claimed. Yet, they were worn by some warlords and proudly displayed. Was it because of better performances compared to native armour? This misconception comes from the fact that a few of these Nanban cuirasses were bullet tested. But such feature is not unique to Nanban dō, in fact the Japanese already did have their own version of bulletproof cuirasses by the 1600s.

So why did the Japanese integrate foreign elements of armour?

A word to describe this is basara (婆娑羅), a trend that originates already in the 14th century but shines of a new light with the influx of exotic goods such as European ones. Ruff collars, European clothes, and elements of exoticness were key to the warrior culture of the time, especially in the capital. Within Japanese armour, kawari kabuto and peculiar cuirasses design such as the Niō dō (仁王胴) are elements that capture this phenomenon. The need to be seen on the battlefield within the Japanese warrior society was key to achieving rewards and merit, and Nanban gusoku had such a function as a show of wealth and exoticness.

In a way, Nanban gusoku can be seen as Turquerie, and in the same way as Ottoman helmets were adopted into the European designs. Not out of pure function, but as a fashion statement.

https://preview.redd.it/u5c8537pl51h1.jpg?width=900&format=pjpg&auto=webp&s=d2b8c4341b97f8bbf625d6a7d80bc0ad0552ede8

Japanese swords: helpless against armor? An overview.

A brief clarification of European influences on Japanese armour: Nanban dō gusoku