Notes on Japanese Armor: The Transition From Lamellar to Plate

Notes on Japanese Armor: The Transition From Lamellar to Plate

A rare ukiyo-e depicting armorers working in the 17th century, from a print of Hishikawa Moronobu (菱川 師宣).

This is a very technical topic that I wanted to discuss here on my blog, since I was asked to but also because it's one of my favorite focus when it comes to history, material culture and ancient technology of Japan.
So today I will write about one of the most crucial aspect of Japanese armor development, a step forward that changed the warfare and history of the country of the rising sun.

Trying to write about Japanese armor history is extremely difficult: we lack a good amount of artistic representations, archaeological findings as well as inventory notes or written descriptions, and much of the knowledge is written inside expensive Japanese books.
To add even more confusion, a great deal of misconceptions have been circulated in the past, which created a very distorted picture that will be addressed here today.

One thing however is quite clear: armors for the torso in Japan went from lamellar to plates over time, from classic armors to tosei gusoku armors, with a complete transition in the 16th century.
To better understand this process, and why it only happened in a specific time period, it is useful to talk about Japanese lamellar armors first.


Japanese Lamellar Armors 

Without taking into account the very early lamellar armors and lacing systems, there were essentially three main ways to make lamellar armor in Japan (and several variations to assemble them which I won't discuss here). So here there are some very simplistic descriptions:

The first one which was the most common and famous in the early armors is to make sane-ita (札板) board using kozane (小札); the small lamellae, when laced together, created a double thickness plate and for this reasons many time an alternated structure of hardened rawhide and metal was used. The board was then stiffened and hardened with lacquer, and laced to other boards to form the armor.

Here you can see how smooth and thick the laced lamellae became after the lacquer is applied, from left to right. At the end of the process, the board became rock solid, and this is why it could be fixed into shape.

The second method is extremely similar but instead of kozane, iyozane (伊予札) were used to make the board. In this case, the overlapping between lamellae was minimal, sometimes reduced to a mere 2mm, and so only metal lamellae were preferred and could be used since without overlapping the weight of the board was reduced. An additional hardened rawhide or metal strip was laced to the back of the board, to increase its strength and to shape the board properly.
The board was lacquered, and then it was encased in leather and laced, or laced and when the armor was finished it was completely encased in leather.

In this damaged section, on the left you could see the small iyozane laced together, with the additional structure at the bottom. On the right, you could see how all of this is covered by layers of lacquer.

The third and final method consisted of using iyozane, connecting them horizontally with leather and silk laces, and then sewing them to a fabric backing; a lot of haidate (thigh armor) were made in this way.

Here on this haidate, the third structure mentioned above. Small lamellae laced horizontaly and sewn to a cloth 

All of these types of structure, (except some styles of the third one) could stay into a fixed shape thanks to the lacquering stiffening or due to the presence of hard strips that acted as structures, and so unlike traditional lamellar which is rather flexible, these armor were semi-rigid when wrapped around the body. So they were able to transfer the energy of an impact through the entire length of the board rather than in one single area, which significantly dissipated the amount of force that was transmitted through to the body of the warrior.

In addition to that, towards the end of the 14th and the beginning of the 15th century, we started to see internal leather ties called tomegawa (停め革) which were used to secure the various boards together, helping to make the cuirass more rigid and to hold it erect. For this reason dō assembled in this manner are sometimes referred to as ‘standing cuirasses’, or tachi-dō (立胴). With the tomegawa, the standing cuirass rested on the hips much better and the weight was equally distributed.

Last but not least, due to the tension of the internal laces, the armor could be opened and closed without the need of hinges; It will flex open and spring back into the original position.

The interior of a iyozane cuirass, assembled in the third method; it is made of lamellae, but is very rigid and doesn't collapse on itself. In this case, the lamellae boards behave very similar to plates. This is the meaning of a  tachi-dō (立胴).

Usually, compared to armors made with rigid and big metal structure like plates, traditional lamellar armors lack a lot of features and this fact make them worst defensive garments.
Lamellar is not rigid: so it would transmit part of the energy of the blow to the body and cannot dissipate the energy through a larger area.
A flexible structure cannot be fixed into shape, so it could not benefit of deflecting curvatures, it is usually closer to the body compared to a rigid structure and the weight is all on the shoulders rather than on the much more comfortable hips.
Finally, the intricate lacing system is subjected to damage over time by weapons as well as the environment.

However, the traditional Japanese lamellar armors as I have explained above didn't have most of the aforementioned lamellar's problems, since their structures allowed them to be rigid and have a fixed, quite resilient shape that make these types of armors able to have almost all the benefits of the ones made with big and rigid plates.
On a practical and functional level, it is easier to understand why the Japanese retained their lamellar armors for such a long period (although it went into several changes through out history) before moving to plate: because their armors worked pretty well.

Unlike with western European armor history, in which is much easier to understand the transition from the flexible mail armor to the rigid plate armor, the benefits offered by plates weren't so neat when it comes to Japanese lamellar armor and it's quite clear to understand why there were few incentives to develop a new structure when the old one worked so well (leaving the technology needed to smelt high quality large plates aside).

In addition to that, lamellar armor and the respective lacing system was the symbol of the warrior social class.
So on a sociological level, the colorful suit of armors were essentially part of the cultural identity of the Samurai, and the aesthetic of kozane was deemed to be a sign of nobility. 
This two levels help to understand why lamellar prevailed for so long in Japan.





The transition to plate

An extremely important element required to create armors made of plates is the level of metal smelting technology. What is often said about plate armor development in Europe, is that one of the key feature needed was the ability to create large, high quality steel and iron plates. Although I don't argue with that idea, I would like to point out that this is not the main feature nor the primary cause of such development.
In any case, the Japanese didn't faced those problems, which is a myth often repeated on the internet. As I have written in my series about "Ancient Iron and Steel technology in Japan" they had the furnaces able to create such high quality plates very early in their history, and the process utilized to make large steel and iron ingots was already well established by the 14th century.

In fact, quite large iron and steel plates were used in Japan to make rigid armors as far as the 5th century with the tankō armor (短甲). It is fair to point out that the plates used in that period wouldn't have been on par with the plates used 1000 years later in terms of quality, and like the lorica segmentata in Europe, these types of armor were replaced with a much easier to make version (lamellar in Japan, mail in Europe); but this is a topic for another article.
Relative big plates were also used in the Samurai age, and could be found in armor for the legs, arms, face and other auxiliary forms like the waidate plate of the Oyoroi.

An example of a Tankō cuirass made with big and large solid plates, 5th century.

Nanbokucho period - mid 14th century

Despite the few incentives and the high level of protection of Japanese lamellar armor, the first development of plate cuirasses in Japan during the Samurai age happened in the 14th century, during the Nanbokucho period (南北朝時代).

In the well known book Taiheiki (太平記) written during the mid 14th century, we could read the terms "kana dō" and "kara dō" respectively written with the characters "金胴" and "空胴".
The first character could be translated as gold, but could also refer to metal, while the second means empty.
So it is assumed that these two words refers to an all metal clam shell cuirass devoid of laces (empty), unlike the traditional armors, and it is accepted that this armor was made with solid riveted metal plates, hinged at one or more sides.
This was a step towards the direction of transitional armor of the 16th century, such as the design found in Mogami dō. In fact it was theorized by Y. Sasama that this type of construction was the forerunner of the aforementioned armor, but unfortunately there are no survivals and we are left with speculations on the meaning of the word.

It is not a surprise that the first step in this direction happened in the wars of 14th century; within this period there was a shift from mounted archery and light infantry warfare to heavy infantry and heavy cavalry based combat, and although arrows were still the most effective killer, polearms of various types and sizes were widely used, so the laces of the lamellar armors could effectively be damaged in the long run, by weather or edged weapons. This was the biggest limit of traditional Japanese armors (and any type of lamellar armors), and having large, sturdy riveted plates eliminated the problems of laces.

A sketch made by me of a possible type of Kana dō; the plates are supposed to be riveted. I'm not an artist but this should give you an idea.

Ōnin war period - late 15th century and eaearly 16th century

After the Nanbokucho period, armor developments slowed down due to the long period of peace.
However, with the outbreak of the Ōnin war and the beginning of the Sengoku period in the late 1470s, armorers had to face new&old problems.
The wars of this period started to be true military campaigns, and in the long run, laced armors, much more than in the 14th century, were deemed to be unsuited for these new types of conflicts. Quoting Sakakibara Kōzan from his masterpiece on Japanese armors,

"[...] When soaked with water they are very heavy and cannot dry quickly, so that in summer the weight is oppressive and in winter the whole may freeze. Moreover no amount of washing will completely free the lacing from any mud which may have penetrated it, so that on a long and distant campaign it becomes evil smelling and overrun by ants and lice, with consequent ill effects upon the health of the wearer."

These facts allowed the creation of a new type of lacing system, the sugake odoshi, which partially solved the aforementioned problems and also decreased significantly the amount of time required to lace an entire suit of armor, but is not the main focus of this article.

Another problem was that with the all country at war, the demand of armors increased drastically.
Lacing an entire board of saneita required a lot of time, and it was only the starting point.
In addition to that, repairing it if needed required time too, and when one of the vertically connected lamellae was broken, the whole ensemble or area was prone to disintegrate.

So the armorers of this period, thanks to the improvement of iron and steel working techniques, started to use slightly curved iron and steel plate called itamono (板物) almost universally in lieu of the old saneita, for the cuirass as well as for the tassets and sode (pauldrons).
To answer to the sociological needs of the Samurai, these plates were sometimes decorated with lacquering to resemble kozane or iyozaneita and due to this application, they are called kiritsukekozane (切付小札) or kiritsukeiyozane (切付伊予札).

These innovations were a throwback of the previous century Kanadō, and gave rise to the Mogami dō (最上胴) at the end of the 15th century and beginning of the 16th century (1520s).
The Mogami cuirass was made by well-forged iron or steel plates. A dō made of rigid metal plates can of course not be opened that easily as when constructed of the more fexible kozane.
This lead to the adding of several hinges – located in four "axis", which results in four dō segments and for this reason it is called a gomai dō– which allow the rigid dō to open easily. 
It was a practical solution, each plate had their own small hinges at the two extremities, and the plate was connected by them to the other plates horizontally, while it was laced vertically by kebiki or sugakeodoshi with tomegawa knots in order to stand rigid and not telescope on itself.
Further development after the 1550s: the major difference from the armor worn earlier, like the Kana dō, was an increase in the number of rows that encircled the torso from 4 to 5.

According to Sakakibara Kōzan the term "Mogami" goes back to the fact that such dō were initially made in the Mogami region of northern Dewa province.

The laced Mogami type of construction; on the left, how the plates were individually hinged at each end. On the right, a Mogami cuirass.

However, in order to answer to the lacing's problems aforementioned, occasionally these plates were riveted instead of being laced, just like the previous Kana dō; whit this addition, a much more solid and rigid cuirass was created.
One drawback to the Mogami construction was that the small individual hinges were delicate and were easily damaged. Despite this they continued to be produced as long as armor was made. To counter this weakness, the small hinges were replaced by larger, longer ones that connected all the plates together. It was not long before the construction was simplified by fitting only one hinge under the left arm.
By this point, by the early 16th century, the Japanese had already access to clam shell dō made with laminated plates.


Sengoku period - mid to late 16th century

After the riveted and laced Mogami dō began to spread in the various armies of the country, and a further development in iron and steel production, it didn't take long for the armorers to have new ideas.
Around the 1560s and the 1570s we start to se the early model and forerunners of the famous Okegawa dō (桶側胴). 
An Okegawa-dō was made of riveted bigger plates; it was robust and relative easy to make and so it became quickly adopted from the late Muromachi period onwards. These early versions also known as Kanto go mai dō (関東五枚胴) were the evolution of Mogami cuirasses, hinged at four places, a five dō sections. 

The later version of the Okegawa-dō in turn is just hinged with one long hinge at the left side of the cuirass and so it is principally a nimai-dō. The plates of an Okegawa-dō can be arranged horizontally (yokohagi, 横矧) or vertically (tatehagi, 縦矧).
These new armors however, had also a different shaping, and were much more towards a globose shape to better deflect weapons, which was established at the end of the 1580 and beginning of the 1590.

A sketch of a yokohagi okegawa dō, made with riveted plates.

With the Okegawa dō, the production time of armors decreased and it is not a surprise to see that said armors were used both by high ranking Samurai as well as by normal foot soldiers by the Keichō era (1590-1610).
It didn't take longer to make the next logical step in armor design; using a full, single plate instead of a series of riveted plates.
The Okegawa as well as the Mogami could be considered two types of laminar armors, like the European Anime cuirass.
Compared to a breastplate made with a single plate, in theory, the laminar one is structurally weaker because the shock is absorbed by one smaller lame instead of a single plate, and each rivets is a potential failure point.
However, in practice the difference between the two types of armor is minimal, because part of the shock is still distributed among the various plates; in fact, even in Europe, Anime cuirass were still used alongside the single plate design. In addition to that, laminar armors are much easier to repair compared to the ones made with one plate.

In any case, around the 1590s  we start to see the production of one plate breastplate, hinged at one side like the Okegawa.
These models are called Hotoke dō (仏胴). This term, "Hotoke", is also used to describe an Okegawa do which is heavily lacquered, with a smooth face not showing any seams, and the words refers to the "unblemished Buddha". The armor underneath is either made of one plate or looks like if made of one plate.

A sketch of a very simple and plain Hotoke dō.

Interestingly enough, within this period, we also have the first contact with European traders. This fact led various armor's historians to question themselves whether or not cuirasses made with one plate were influenced by Western armor.
One could see the Hotoke-dō in the context of Nanban-dō (南蛮胴 - western style cuirass), quasi as a product of emulating these Western armors whose face is also made of one plate, and other could see it in the context of a further simplification of armors, namely quasi as the next logical step from the Mogami-dō of laced plates over the Okegawa-dō of riveted plates.

If I have to pick one of these versions, I'll go with the latter; we knew that European armors influenced Japanese ones, and they were called with a specific name (Nanban), had a different shape and were likely to be first seen in Japan around the 1590s, so the Hotoke style happened around the same time and is hard to claim direct influence.
While the concept of making larger plates was the leitmotif of the whole process of simplification started in the 16th century, both in cuirasses as well as in helmets.


In any case, around the 1590s we see the final iterations of plate cuirasses in Japan.
The aforementioned Nanban dō (南蛮胴) style was used by some Samurai; some of these armors were directly imported from the European, although they were an extremely tiny minority (but this is a topic for another article), while the majority of the Nanban dō were actually made by Japanese armorers. 

These armor are called Wasei Nanban dō (和製南蛮胴) or Nihonsei nanban-dō (日本製南蛮胴),  which means Japanese made Nanban-dō. Some of them followed their European models faithfully but the majority were adjusted to meet Japanese aesthetics. Japanese-made and European-made Nanban-dō consist basically of two thick iron plates with a central ridge line, which made the weapons of the enemy sliding off upon impact and so this feature was also occasionally applied to other styles of armors, like the Okegawa. In this case, we speak of an Hatomune-dō (鳩胸胴).

A sketch of a Nanban breastplate.

While in the context of the Hotoke dō, we see the appearance of the famous Niō dō (仁王胴), which was made of a single plate and embossed to like like a Niō.
In the context of the Tatehagi Okegawa and Mogami dō, we could see the development of the Sendai dō (仙台胴) also known as Yukinoshita dō (雪の下胴); this armor was made with five large plates: one for the front, one for the back, one for the left side, and two for the right side where the breastplate open; due to this feature this style is a type of gomai dō, like the Mogami dō. Sometimes, instead of one single large plate for each sections, riveted plates were used. This armor is famously associated with Date Masamune.

On the left, a Sendai Dō, hinged at four sides and made with multiple large plates. The sape was more similar to the Mogami dō. On the right, a Niō dō, made with only two plates and hinged at one side, embossed and decorated.

At the beginning of the 1600, the development of tosei dō was completed, and various mixed styles with several possible iterations emerged in the last years of the Sengoku period.



Common misconceptions associated with the transition to plate armor in Japan

Even if this detailed version of mine could be seen in various books and papers about Japanese armors, and it could be shared by a good number of scholars, unfortunately it is not the mainstream one.
With the need of a very broad generalization in this field, a good number of misconceptions have been circulated around on the internet in order to explain the transition and development of tosei gusoku cuirasses; even if there is plenty of material above, for the most curious, I'll try to debunk them;

1) Japanese armorers started to use plate due to the presence of firearms in the 1540s.

As I have explained above, the usage of plates in Japanese armors could be dated as back as the 4th century,  and early 16th century. Solid clam shell cuirasses were developed in the late 16th century, and likely there were already some early development in the 15th century, while early firearms didn't play any significant role up until the 1560s, with being established weapons by the 1580s, as I have written here in my article about the real spread of gunpowder weapons in Japan.
It wasn't the so called gun paranoia to drive Japanese armor makers into plate, but the need of simplification in the production process. Moreover, lamellar armor were still being made fairly regularly.
Although it is fair to say that larger plates were better suited to withstand bullets than lamellar structures, so I do understand why such wrong correlation was made in the first place.

2) The Japanese armorers made tosei gusoku thanks to the inspiration of European armors.

While it would be wrong to underestimate the impact of Western influence into modern armor, it is equally wrong to find in them the starting point of Japanese armor development.
It is a common misconception to attribute the Okegawa, Hotoke and other styles of cuirass to the European, but in reality, Western armors were rare and didn't came into Japan prior to the 1590s, while we start to see the aforementioned styles around the same time, as a result of a much more complicated economic process, which would be naïve to ignore.


3) The Japanese were able to make tosei gusoku armor thanks to European's techniques and materials.

While I have already address the old myth of the Japanese iron being poor in quality, there wasn't any significant improvement brought by the Europeans, as far as any sources is concerned, to Japanese steel and iron industry: neither by techniques nor by any "magical superior steel" imported.
By the time the European arrived, the Japanese were already able to smelt high quality steel ingots large enough to make plates thanks to their own native blast furnace, in fact they were able to make their own Japanese made western style armors by the 1590s.



If you managed to read it all until here, I wanted to seriously thank you for the time you dedicated to this long, very technical article.
Please feel free to share it, in order to remove these misconceptions on the internet, and for any question don't hesitate to use the comment section below!
Thank you so much, I hope you liked it!

Gunbai