Japanese Armor: O-yoroi, Do-maru, and Tosei-gusoku — How They Differ
Japanese armor is not one suit but four successive types. O-yoroi was worn by the mounted archer of the Heian period, do-maru and haramaki were made for foot combat, and tosei-gusoku appeared in the Sengoku period, when arquebuses took the field. All of them are assembled from the same parts: helmet, body, shoulder guards, arm guards, and greaves.
Armor in Japan changed not with fashion but with the way battle changed. While warriors fought on horseback and shot bows, the body was made boxy and rigid. When combat became foot-based and massed, armor slimmed down and fit the figure. When firearms arrived, the chest became solid and thick again.
Four Types of Armor Worth Distinguishing
| Name | Writing | When worn | For whom and how it differs |
|---|---|---|---|
| O-yoroi | 大鎧 | 10th–14th centuries | Armor of the noble mounted archer. The body is boxy, and the wide o-sode shoulder guards cover the arm when drawing a bow. Heavy: by various estimates 25–30 kg |
| Do-maru | 胴丸 | 12th–16th centuries | Wraps around the body and fastens under the right arm. Made for foot soldiers, later worn by nobles too — lighter and more mobile than o-yoroi |
| Haramaki | 腹巻 | 14th–16th centuries | Wraps not at the side but at the back. The lightest variant; the back opening was covered by a separate plate |
| Tosei-gusoku | 当世具足 | 16th–19th centuries | "Armor of the present time." Large solid plates instead of small scales, designed for bullets and mass production |
By what feature they are classified
The main feature is how the armor is put on and what it protects first. O-yoroi, do-maru, and haramaki differ in where they fasten: at the side, on the right under the arm, or at the back. Tosei-gusoku stands apart: it is no longer a development of the previous scheme but a response to the arquebus. The best examples of such armor were tested by gunshot, and a dent on the chest plate was not a defect but a mark of quality.
What the Armor Is Made Of
The set is called gusoku — "completeness, assembledness." The parts are the same for all four types; only the proportions and materials differ.
- Kabuto (兜) — helmet; at the back a neck guard shikoro is attached, and on the sides "wings" fukigaeshi are often turned back
- Do (胴) — the body, the main part; the whole type of armor is named after it
- Sode (袖) — shoulder guards; on o-yoroi they are wide and almost replace a shield
- Kote (籠手) — arm guards: a woven sleeve with sewn-on plates and chainmail
- Kusazuri (草摺) — a "skirt" of hanging strips covering the thighs
- Haidate and suneate — thigh guards and greaves, appearing in later sets
What menpo is
Menpo (面頬) is a mask for the lower half of the face, from chin to cheekbones. It has two tasks, and the second is more important than the first: to protect the face and to give support to the cord with which the helmet is tightened — without the mask the knot under the chin would come loose. Outside, the mask was given a fierce expression and a mustache of horsehair; inside it was often coated with red lacquer. A mask for the whole face is called somen, a shortened one — hambo.
鎧 and Words You Will Meet in a Museum Label
鎧 — значение: armor, plate armor, to put on armor — онъёми: カイ、ガイ — кунъёми: よろ.う、よろい — 18 штрих(ов). 鎧 — "armor, plate armor": 18 strokes, on the left the radical "metal" 金. By itself it reads yoroi; in compounds it gives kai and gai.
| Japanese | Reading | Translation |
|---|---|---|
| 鎧 | yoroi · yoroi | armor, plate armor |
| 甲冑 | katchū · katchū | armor and helmet as a single set (museum and scholarly term: this is how exhibits are labeled) |
| 兜 | kabuto · kabuto | helmet |
| 具足 | gusoku · gusoku | a complete set of armor |
| 武具 | bugu · bugu | military equipment in general |
| 腹巻 | haramaki · haramaki | armor that wraps at the back (in modern language the same word means "stomach band, belly belt") |
How these characters are read
For 鎧 and 兜 the Japanese readings are yoroi and kabuto, and they are heard in speech. The Chinese readings surface in compound words: 甲冑 katchū, 鎧甲 gaikō. If a museum label says 当世具足, that is literally "gusoku of the present time" — armor of the Sengoku period.
Write 鎧 along the guides: the radical "metal" on the left, and the trainer suggests the stroke order.
Weapons and Martial Ways in This Section
Armor is half the topic. Alongside it in this section are blades, polearms, and the schools that mastered all of them: they are covered on separate pages, with links collected below.
Where to see authentic armor
The largest collection is in the Tokyo National Museum: it has both Kamakura-period o-yoroi and tosei-gusoku. Part of the Japanese collections has been digitized in the e-Museum database. Individual sets are kept at Shinto shrines: they were donated after victories, which is why many have survived intact.
FAQ
- What types of Japanese armor are there?
- There are four main types. O-yoroi is the heavy armor of the mounted archer of the Heian period. Do-maru and haramaki are lighter, for foot combat, and differ in where they fasten: under the right arm and at the back. Tosei-gusoku is armor of the Sengoku period with large solid plates, designed to withstand a bullet hit.
- How much did Japanese armor weigh?
- O-yoroi is estimated at 25–30 kg: it is a rider's armor, whose weight is carried by the horse. Do-maru and haramaki are noticeably lighter, around 10–20 kg, because they were worn fighting on foot. Tosei-gusoku was made in various weights — from light sets for ordinary ashigaru to heavy ones tested by gunshot.
- What is menpo?
- Menpo is a protective mask for the lower part of the face, from chin to cheekbones. Besides protection, it held the helmet cord: without support the knot under the chin would come loose. The mask was made with a fearsome expression, a mustache of horsehair, and a removable nose. The full-face version is called somen, the shortened one — hambo.
- How is "armor" written in Japanese?
- The main word is 鎧, read yoroi. In museum labels 甲冑 katchū is more common — "helmet and armor" as a single set. A full set of equipment is called 具足 gusoku, and all military equipment in general — 武具 bugu.
- Where to start understanding the topic?
- With two questions for any armor: how it fastens and what kind of combat it is designed for. The answers immediately give the type and period. Then it is easier to go by parts — helmet, body, shoulder guards — because they are named the same in all types, and the museum label becomes readable.
Sources
Updated: 2026-09-10