Iron Tsuba of the Koto Period: Origins and Functional Beauty in Heian and Kamakura Swords

The Birth of the Tsuba—Its Origin as a "Hand Guard" Protecting the Blade

The origin of the tsuba is inseparably linked to the birth of the Japanese sword. When the curved tachi became established in the late Heian period (10th–11th centuries), some form of barrier became necessary at the junction between the blade and the tsuka. The "hand return" (tegaeshi)—a protective function that prevented the hand from sliding toward the blade during combat and protected against enemy blades and one's own fingers—was the tsuba's original role.

The earliest tsuba were extremely simple iron disks. Decoration was minimal, consisting only of a hole through the center to accommodate the nakago, and a flat area called the "kirihaidai" for fixing the tsuba when sheathing it in the saya. This function-first form became the foundation for old sword period tsuba.

The choice of iron as the material was clear. Compared to copper or brass, iron was difficult to work with but possessed both hardness and resilience, enabling it to withstand the strikes of actual combat. The practical-minded values of Heian warriors were directly reflected in the choice of materials.

Tsuba in the Late Heian Period—The Rise of Samurai Culture and Changes in Blade Fittings

In the late Heian period (12th century), as samurai society rose to prominence through the Genpei conflict, the importance of the entire blade fitting increased. Tsuba from this period are collectively called "kotetsu tsuba," but existing examples are extremely rare, with most intact examples carefully preserved in museums and temples and shrines as treasures.

The basic forms were circular or elliptical, with most measuring about 6–8 centimeters in diameter. The thickness was relatively substantial at around 5–10 millimeters, the result of prioritizing practical use on the battlefield. Thin tsuba risked cracking under the impact of strikes, while overly heavy ones compromised the maneuverability of the entire blade. Long experience produced an optimal "type" in dimensions and weight, which was passed down to blade fitters throughout the regions.

Ingenuity also began to appear in the form of the edge. Styles emerged such as the thin-finished edge type and the rounded-rim type, with regional styles beginning to develop centered on sword-making regions such as Kyoto, Yamato, and Bizen.

Tsuba in the Kamakura Period—From Practical Beauty to Sculptural Beauty

The Kamakura period (1185–1333) saw important developments in the form and technique of tsuba. The stability of samurai rule and the refinement of samurai spirit deeply influenced the aesthetics of blade fittings.

A particularly noteworthy concept from this era's tsuba is "hone-bami." This refers to a technical and aesthetic refinement where the periphery of the tsuba and the area around the nakago hole are carefully narrowed to reduce weight while maintaining strength. This represents the process of elevation from mere iron mass to a sculpted form imbued with functional beauty. The sophistication beginning to bud amid the ruggedness reflects the spirit of the age inscribed in the tsuba's contours.

Also, from the Kamakura period through the Muromachi period, "sukashi"—a technique of creating patterns by piercing holes in the iron—appeared on tsuba. The earliest sukashi primarily consisted of round holes or elongated holes, combining the practical purpose of weight reduction with decorative appeal. These gradually developed into complex piercing depicting family crests and natural forms—wood sorrel shapes, sword shapes, wheel shapes, and comma shapes—laying the foundation for Japan's unique metalworking art.

It is thought that the specialized profession of "tsuba-shi" (tsuba maker) became gradually independent during this period as well. Division of labor progressed from the initial stage when sword smiths also made tsuba, and regional schools began to develop their own stylistic traditions—a major characteristic of the Kamakura period.

Appreciation Points for Old Sword Period Tsuba—Reading the "Era" in the Base Metal

The greatest appeal when appreciating old sword period tsuba lies in the "flavor of the jigane."

The old patina (ko-iro) formed over many years displays a complex range of hues from dark brown to reddish brown, revealing diverse expressions depending on the angle of light. The iron surface bears patterns called "chikei" where the internal structure of the iron appears on the surface—an aesthetic element corresponding to the jihada of the blade itself. The traces of folded forging emerge as flowing patterns and straight-grain patterns, and the tsuba itself stands as a complete work of iron craftsmanship.

The thickness and weight of the tsuba, the finishing of the edge area, the precision of the nakago hole—all of these speak to the maker's intention and skill. In particular, the nakago hole was carefully adjusted to fit the blade's nakago, and the precision of this fitting serves as evidence of the metalworking standards of the time.

Many old sword period tsuba bear fine scratches and impact marks from actual use. These are evidence of the blade fitting's function in battle and embody historical reality. Among collectors, many place particular emphasis on these marks of use as "witnesses to the era," and the absence of later repair traces becomes a condition for high valuation.

Major Collection Institutions for Extant Old Sword Period Tsuba

Opportunities to actually see old sword period iron tsuba are limited, but the following represent major holding institutions:

• Tokyo National Museum: National Treasures and Important Cultural Properties of blades and blade fittings are displayed in permanent and special exhibitions. Old sword period blade fittings are periodically displayed with detailed explanations, allowing systematic appreciation.
• Kyoto National Museum: Materials related to sword culture centered on Kyoto are abundant. Old blade fittings transmitted to Kyoto temples and shrines are also held and displayed, making it a valuable venue for comparing regional stylistic differences.
• Nezu Museum (Tokyo): Holds one of Japan's finest collections of blade fittings. Old iron tsuba from the Kamakura and Muromachi periods can be appreciated systematically.
• Treasure halls of Kasuga Taisha and Atsuta Shrine, among others: Blades and blade fittings donated over generations have been preserved, and can be viewed at special exhibitions. The Kasuga Taisha National Treasure Hall displays masterpieces of old blade fittings.

As of 2026, specialized sword museums have also developed significantly, with public access to materials including old iron tsuba increasing throughout the country. If possible, close observation of actual objects—experiencing the color and luster of the jigane and its weight—is the best way to deepen one's understanding of old sword period tsuba.

Conclusion—The Ancient Spirit Dwelling in Unadorned Iron

Old sword period iron tsuba possess a "simple strength" absent in the more decorative metalwork tsuba of later ages. In contrast to the precise chasing and inlay work of Edo period tsuba, old sword period tsuba are stripped of all excess. Yet within the rugged iron lies the crystallization of the tension of the battlefield for which Heian and Kamakura warriors risked their lives, and the technical achievement of craftsmen who forged each strike with sincerity.

What remains after ornament is stripped away—the old sword period iron tsuba answers this question in silence. The unadorned outline of iron speaks across the ages of the essence of Japanese sword culture. Due to their rarity, old iron tsuba command high collector value and represent an ultimate collecting goal for many collectors. This derives not from mere desire for rarity but from deep respect for placing in one's hands the history of Japanese iron itself.