Sword Blade Engravings (Horimono): Types, Meanings, and Techniques——Kurikara Dragons, Buddhist Letters, Grooves, and Sword-Wrapped Dragons

What Are Horimono (Blade Engravings)?——Faith and Technique Carved into Sword Steel

Engravings carved onto the surface of Japanese sword blades are collectively known as "horimono" (彫物). While modern viewers often perceive them as decorative elements, their true nature carries profound religious and talismanic significance. They represent a complex form of expression combining the faith of swordsmiths and patrons, warriors' prayers for divine protection, and the technical pride of the craftsman.

By convention, engravings are applied to the blade portion above the tang (nakago), from the edge-bottom area (hamachi) to the point vicinity (boushi), carved into the upper and/or lower surfaces of the ridge (shinogi). While the presence or absence of engraving is an important factor in assessing the value of a Japanese sword, issues such as "shallow carving" or "post-production engraving" (nochihori) can become negative factors in authentication.

Major Types of Engravings and Their Significance

Kurikara Dragons

One of the most representative engravings is the "kurikara dragon." This depicts a dragon coiled around the three-pronged sword (sankokan) of Fudō Myō-ō (the Immovable One). "Kurikara" derives from Sanskrit and is also the name of the black dragon said to be an incarnation of Fudō Myō-ō.

In kurikara dragon engravings, the dragon typically coils from the sword's point toward the hilt, with flames rising from the blade. This composition symbolizes "the immovable power to sever evil," making it a favored motif among warriors seeking divine protection in battle.

Carving kurikara dragons requires advanced skill, so specialist craftsmen called "horishi" (engravers) typically handled this work. While swordsmiths sometimes carved them personally, a division-of-labor system was standard, and particularly from the Edo period onward, engravers became established as an independent profession.

Buddhist Letters (Bonji)

Bonji are Sanskrit characters representing Buddhist deities. In Japan, they have been used as talismans since the Heian period. Engraving bonji on a sword blade meant installing the bearer's protective deity or principal Buddha on the blade itself.

Representative bonji and their corresponding deities:

• The "A (阿)" character: seed syllable of Vairocana Buddha
• "Kāṃ": seed syllable of Fudō Myō-ō
• "Vam": Vairocana (Garbhadhatu realm)
• "Kiriku": Amida Buddha
• "Uṃ": Bishamonten

Bonji are typically carved into the flat surface of the ridge (shinogi-ji) or ridge line (shinogi-suji), sometimes appearing as standalone engravings or combined with kurikara dragons.

Among bonji, "Kāṃ" (Fudō Myō-ō) holds a special position. In Esoteric Buddhist rituals, wooden talismans dedicated to Fudō Myō-ō are cast into flames to burn away earthly desires. The concept underlying bonji engraving on swords was to view "the blade itself as such a talisman." This reflects a spiritual equivalence: the warrior's act of cutting down enemies on the battlefield is equated with Fudō's flames purifying defilements and demonic obstacles.

Hi (Grooves)——The Most Popular Engraving

Grooves called "hi" represent engravings combining practical function with aesthetic appeal. Hi are grooves carved vertically along the flat surface of the blade (hiraj), classified as follows according to their shape:

Straight grooves (bohi): A single linear groove, the simplest and most widely seen type. Most commonly extend from near the spine-edge area (munemachi) of the tang to just before the point area (boushi).

Double grooves (futasuji-hi): Two parallel grooves, often combined with straight grooves in a configuration called "straight groove with accompanying groove" (bohi ni soe-hi).

Lower grooves (koshi-hi): Short grooves carved only on the lower half (lower section) of the blade.

Extended grooves (kakitoshi): A form extending the groove to the center of the tang, with the advantage that the grooves are less likely to be worn away by polishing.

There are various theories about the function of hi, with the main effects cited being: blade weight reduction (creating a difference of approximately 1-3 grams), adjustment of blade flex and stiffness, and reduction of air resistance during drawing and sheathing. However, modern scholarship increasingly supports the view that aesthetic and spiritual significance were primary, with practical function secondary.

Among ordinary people, grooves were also colloquially called "blood grooves" (chimizo), based on the folk belief that "blood would flow when the blade was thrust, allowing it to be drawn more easily." Modern experimental research has largely debunked this theory. However, folk religious interpretations viewing grooves as "channels to dispel bad blood and impurity" also spread during the Edo period, with examples of grooved blades being preferred in magical contexts. Furthermore, in Zen Buddhism, the grooved blade appears in metaphorical discussions of "cutting through with one stroke," where the blade is described as "a pure vessel severing delusion." Thus practical function, aesthetic appeal, and spiritual significance layer together in this simple groove.

Sword-Wrapped Dragons (Kenmaki-ryū)

Apart from kurikara dragons, the sword alone, or dragons depicted without coiling around the sword, are sometimes carved. In sword-wrapped dragons, a dragon coils around a sword, and while this term is sometimes used interchangeably with kurikara, technically the direction of the dragon and the expression of flames differ.

Fudō Myō-ō Statues and Protective Deities

Full-round carvings of figures, deities, and Buddhas are called "marubori" (full-round carving) or "takabori" (high relief). Standing figures of Fudō Myō-ō are most common, with some examples showing triadic compositions including attendant protective deities (Kongara and Seitaka). These require advanced skill, and works by renowned Edo-period engravers such as Nara Masanao and Yanagawa Naomasa are known as masterpieces.

Often overlooked alongside Fudō Myō-ō and protective deities is the motif of "the dove of Hachiman Bosatsu" (Hachiman Daibosatsu). The practice of engraving doves, messengers of Hachiman, on sword blades shows a particularly deep connection with naval military leaders, with records indicating that commanders fighting at sea sought to install Hachiman's protection on their blades. Solo dove engravings are rare, but examples combined with tomoe and wave motifs carved on the blade's lower section have been documented in surviving specimens.

Classification of Carving Techniques——From Hair-Line Engraving to Full-Round Carving

The major carving techniques used for Japanese sword engravings can be divided into five main types:

Hair-line engraving (kebori): A technique expressing designs through fine outline lines. Subtle variations in line thickness and depth create a sense of three-dimensionality. It requires the most precise technical skill and excels at detailed expression.

Flat chiseling (katakiri-bori): A technique using only one side of the chisel to create asymmetrical grooves in cross-section. By carving deeper on the edge (shinogi) side and shallower on the ridge (mune) side, shadows emerge according to how light strikes the surface. This technique is frequently used for expressing bonji.

Mortar-style carving (yagen-bori): A carving technique producing a V-shaped cross-section. The name comes from the shape of a "yagen" (mortar for grinding herbs). Even cuts on both sides produce sharp outlines.

Relief carving (uki-bori): A technique where the background is carved away to raise the design. It excels at three-dimensional expression.

Full-round carving (maru-bori): Three-dimensional carving where the design projects significantly from the blade surface. It requires the most advanced skill and time.

Key Points in Authenticating Engravings

Authentication of engravings requires observation of the following points:

Post-production or contemporary carving: Determining whether the engraving was carved when the blade was made (contemporary carving) or added later (post-production carving). In post-production carving, the surface texture (hadatachi) of the base steel (jigane) around the engraving may differ from the surrounding area, and unnatural qualities may appear at the rust line (sabigiwa) of the blade.

Depth of carving and age-related changes: When carving has become shallower due to polishing, the number of polishings can be estimated from the degree of change. Special attention should be paid if the corner sections of bonji have become too smooth.

Identifying the engraver: Works by renowned engravers from the Edo period onward can sometimes be attributed to specific lineages based on carving characteristics and the finishing of ridge grooves.

Historical consistency: Confirming that ancient blades have not been fitted with anachronistic engravings. Kurikara dragons and bonji are more common from the Kamakura to Nanboku-chō periods, while dragon, wave, and chrysanthemum water motifs tend to increase in the Edo period.

Evolution of Engravings Through Historical Periods

The popularity of engravings changed significantly across historical periods.

Kamakura to Nanboku-chō period: Kurikara dragons and bonji were the mainstream, with strong talismanic character. Straight grooves were standard.

Muromachi period: Engravings began to diversify. Double grooves and lower grooves appeared. Wave and dragon motifs increased.

Momoyama to early Edo period: Ornate patterned carvings became fashionable. Reflecting the cultural atmosphere of the Toyotomi and Tokugawa regimes, kurikara dragons became increasingly detailed and high-relief techniques advanced.

Mid to late Edo period: Engravers became established as independent craftsmen. Works by renowned engravers were highly prized, and engravings began to be appreciated as artworks independent of the blade itself. Decorative motifs such as chrysanthemum water, waves, and dragons came into frequent use.

From the Meiji period onward: After the Edict Prohibiting Swords, demand for engravings temporarily declined, but their value was reassessed through the sword-arts movement. Contemporary smiths also create spiritually significant engravings, though individual artistic expression is now valued over precise reproduction.

In the modern era, sculptors of engravings (horishi) are extremely few in number across the nation, with only a handful of craftsmen dedicated solely to blade engraving. Because engravings are by principle applied to blades after polishing, any single mistake compromises the entire blade's value—a pressure-filled undertaking. Contemporary swordsmiths typically outsource this work, and commissions to renowned engravers often entail waiting periods of several years.

Engravings stand at the intersection of beauty and faith in the Japanese sword, representing a unique cultural product. Rather than mere decoration, true appreciation lies in discerning the religious intent embedded within them, the prayers made during their creation, and the technical pride of the swordsmith and engraver.