Oyoroi Complete guide to understand the Japanese Great Armor
Table of Content
What is Oyoroi?
Image source:bunka.nii.ac.jp
O-yoroi is the most iconic type of traditional Japanese armor used mainly during the Heian period (794-1185) and the Kamakura period (1185-1333). It is characterized by its box-like structure body, designed to protect Samurai on horseback.
The word Oyoroi literally means "Great Armor" in Japanese. O usually means "Big" or "Great", and Yoroi means "Armor". The O-Yoroi is also known as "Shikisho no Yoroi" (式正の鎧) in Japanese. ”Shikisho" means formal or official, means that the O-Yoroi is the most prestigious and formal type of armor, and widely used in many ceremonies.
Material of Oyoroi
The main material used on Oyoroi are iron, raw cowhide, tanned deer leather, silk threads, dyes , etc. The higher the rank of the samurai, the more advanced the techniques and materials used in their armor.
Iron, or in some cases cowhide are the material for Kozane (小札 small scales) and some structural parts of the armor. Kozane are small rectangular plates, usually 7-8 cm (2.8-3.1 inches) long and 4 cm (1.6 inches) wide, about the size of a business card. They are the fundamental components of the armor, providing flexibility and protection. A nice set of Oyoroi could use about 4000 pcs Kozane.
Silk or leather cords are used to lace together the kozane, this process is called Odoshige (威毛). This lacing not only holds the armor together but also adds to its aesthetic appeal. Different colors and patterns of lacing give each set of armor a unique look.
Tanned leathers are used on the surface of armor and helmets. They are called Egawa (絵韋). These leathers were dyed with patterns like oblique crosshatching, lions, and Fudō Myō-ō motifs etc. They help maintaining the shape of the armor and preventing the bowstring from catching on the Kozane.
History of Oyoroi
The O-Yoroi first appeared during the mid-Heian period (794-1185) in Japan. It was designed specifically for mounted samurai warriors engaged in “Kisha-sen 騎射戦”, the mainstream style of warfare in that time. It’s like duel in the West, samurai will introduced themselves, drew their bows (Yumi), and shot arrows at each other as they passed by.
To fit this style of battle, Samurai's armor should be good at two things, the ease of drawing a bow and the effectiveness of the armor in deflecting arrows. The O-Yoroi had several special features designed for horseback archery and arrow protection. For example the Tsurubashiri no Kawa (弦走韋 String Running Leather) on the chest to prevent bowstring from catching on the Kozane. It included large shoulder guards (sode), side guards (waidate), and chest plates (kyubi no ita and sendan no ita) to deflect arrows. The armor also featured kusazuri to protect the lower body while allowing for ease of movement on horseback.
During the Kamakura period, the width of the Oyoroi chest piece (Do), which was previously the same from top to bottom, began to taper more towards the waist for better mobility on horseback.
In the Nanboku-chō period (1336-1392), as warfare tactics shifted to larger scale battles, making long-range weapons like the yari (spear), naginata (polearm), and even the katana (sword) more commonly used. Lighter and more practical armors like haramaki and Domaru became popular. By the Muromachi period (1336-1573), O-Yoroi was mostly phased out from battlefields. In the peaceful Edo period, it became more decorative, symbolizing the samurai class and their heritage.
Major parts of Oyoroi
The hoshi kabuto (star helmet) and later the suji kabuto (ridged helmet) were the most common kabuto to pair the O-Yoroi. Both types featured a helmet bowl (鉢 Hachi) made from iron plates, with a shikoro (neck guard) composed of Kozane (small plates) attached to the bottom.
Under the helmet, Samurai usually wear a soft eboshi cap, their hair was styled into a topknot (motodori) and pulled through the hole at the top of the helmet (tehen) along with the eboshi. However, this design is no longer used in later designs .
吹返（Fukikaeshi / Ear）
The "fukikaeshi" on the helmets used with O-Yoroi armor were made quite large to protect the face from enemy arrows. As battles shifted to ground combat and arrows were used less, the fukikaeshi became smaller to improve visibility.
錣（Shikoro / Neck）
The shikoro is made of small metal plates attached to the bottom edge of the helmet. It protects the neck from attacks like arrows from behind. In early Kabuto, the shikoro faced downward, but over time, it was changed to face sideways.
前立（Maedate / Front Crest）
Maedate is the front crest placed on the front of the Hachi, it’s the earliest type of Tatemono. For Oyoroi, the "kuwagata" (鍬形) were commonly used.
大袖（O Sode / Shoulder）
The main role of the "O-sode" (large shoulder guards) was to protect samurai from enemy arrows. Mounted samurai, who primarily used bows, couldn't hold a shield to defend themselves, so they used the O-sode as a shield instead.
They would twist their bodies to deflect arrows with the O-sode. In the Heian period, the O-sode measured around 33 cm (13 inches) wide and 40 cm (16 inches) long. By the Muromachi period, they grew to about 35 cm (14 inches) wide and 42 cm (17 inches) long. However, as close combat became more common, the O-sode became cumbersome and were made smaller or left out in "Tosei gusoku" (modern armor).
籠手 (Kote / Arm)
Kote are arm guards worn to protect the forearms and hands. In O-Yoroi, only one kote is worn to keep the other arm free for better movement and control when using a bow.
肩上（Wada-kami）
The part that extends from the back of the chest, goes over both shoulders, and connects to the "mune-ita" (胸板, chest plate) in the front with a "taka-himo" (高紐, high cord). The shoulder area of the O-Yoroi, called "wada-kami" (肩上), has small plates called "shoji no ita" (障子板) to protect the neck.
胸板（Muna Ita / Chest Plate）
The topmost plate on the front of the chest. Usually made of iron and designed to be very strong.
脇板（Waki Ita / Side Plate）
The iron plate attached to the side to cover the gaps. The "waki-ita" (脇板) of the O-Yoroi is attached only to the left side, and this practice appears to have started in the late Kamakura period.
鳩尾板（Kyubi No Ita）
Since the O-Yoroi was designed for fighting primarily with bows, the chest plate and the "maetateage" (前立挙) below it were made narrow to make it easier to draw the bowstring.
However, this design created a gap between the upper part of the chest and the shoulder, leaving the wearer exposed. To protect this area, Japanese added two more plates called "kyūbi no ita" (鳩尾板) and "sendan no ita" (栴檀板). The kyūbi no ita, placed on the left side of the chest plate, was made from a rectangular iron plate covered in leather.
栴檀板（Sendan No Ita）
While the kyūbi no ita was a rectangular iron plate, the sendan no ita was made from three tiers of small plates (kozane ita) laced together, look like a mini sleeve. This flexible design allows smooth movements, even if the sendan no ita touched the archer's right hand while drawing the bow.
弦走韋 (Tsurubashiri no Kawa)
A piece of Leather (Usually deer leather) attached to the front of the chest, it is designed to prevent the bowstring from getting caught on the small plates when drawing the bow.
脇楯（Waidate）
This is a unique component only features on O-Yoroi. It protects only the right side of the torso, with the area covering the flank made of an iron plate called "tsuboita" (壺板), from which the "kusazuri" (草摺) hangs down. When wearing the O-Yoroi, you should wear the "waidate" (脇楯) first.
立挙（Tateage）
This part protects the upper half of the torso. The front is called "maetateage" (前立挙), and the back is called "ushirotateage" (後立挙). The O-Yoroi has an "agemaki" (総角) tied and hanging from the ushirotateage.
長側（Nagakawa）
This part protects the lower half of the torso around the abdomen. In the case of O-Yoroi, because the waidate (脇楯) is placed on the right side, it is designed in a U-shape to cover the front, left side, and back in one continuous piece.
蝙蝠付韋（Batsukeawa）
It is made of strong leather wrapped in decorative leather (egawa), and shaped like a trapezoid to attach the kusazuri (草摺) on both sides. Because it resembles a bat with its wings spread, in Japanese the name Batsukeawa literally means bat-wing leather.
揺糸（Yurugi no Ito）
The cord used to connect the dō to the kusazuri. In the case of O-Yoroi, it is used to attach the front and back kusazuri.
草摺（Kusazuri）
O-Yoroi has four piece of Kusazuri : front, back, left, and right. These four pieces form a trapezoid-shaped box around the waist. The right kusazuri is attached to the waidate, which covers the right side of the body.
引合緒（Hikiawase no O）
These are the cords used to tighten the Do when worn. In O-Yoroi, they are attached to the front and back of the right side.
胴先緒（Dou Saki no O）
These are the cords attached to the bottom of the do used to tighten and secure it.
