Hair-Pin-Shaped Large Swords——The Unique Sword Form of the Heian Period and Extant Cultural Properties

What Are Hair-Pin-Shaped Large Swords——One of the Most Unique Forms in Japanese Sword History

The "hair-pin-shaped large sword (kenuki-gata-tachi)" is a particularly distinctive presence among Japanese swords made during the Heian period (794–1185). Most Japanese swords are created by making the blade (the metal part) and hilt (the grip portion made of wood, cloth, and metal fittings) separately and then assembling them together, but the hair-pin-shaped large sword was forged as a single integrated iron piece, fundamentally differing from the standard structure of Japanese swords.

The name derives from the shape of the openwork carving applied to the hilt (tsuka). When viewed from the side, an elliptical opening is pierced through the hilt portion that resembles the upper half of a "hair-pin (kenuki)"——a tweezers-like small tool——and this is the origin of the name "hair-pin-shaped (kenuki-gata)." This opening is not merely decorative but is believed to have had a functional purpose of reducing the weight of the integrated iron hilt, however slightly. The aesthetic and practical pursuits simultaneously realized in this single small hole represent the craftsmanship spirit of the Heian period in concentrated form.

The Uniqueness of Structure——Why a Fully Integrated Design?

The hilt of a typical Japanese sword has a structure in which the tang (nakago)——the root portion of the blade——is inserted into a wooden hilt block (tsukaki) and secured with a mekugi (retention pin). In contrast, the hair-pin-shaped large sword is a single integrated forged iron piece where the blade, tang, and hilt form one continuous whole, with no wooden hilt block employed at all.

The integrated structure requires considerable technical difficulty from the perspective of forging technology. In the manufacture of typical Japanese swords, craftsmen can concentrate on forging the blade shape, but with hair-pin-shaped large swords, the entire form must be forged at once, including the length, shape, and position of the openwork that comprises the grip portion. Furthermore, the finish requires precise openwork carving, making these swords testimonies to the high level of technical skill possessed by iron-working craftsmen of the Heian period.

Regarding the practical significance of this integrated structure, various theories exist. One theory suggests it was designed to eliminate the risk of the hilt becoming detached during combat. Wooden hilt blocks are prone to cracking and loosening due to moisture and impact, and during intense clashing there was danger of the entire hilt being knocked away. With an integrated design, this risk could be fundamentally eliminated. Another interpretation proposes that, as a ceremonial or ritual sword for Heian nobility, the design prioritized external simplicity and elegance. An unblemished hilt made of iron, utilizing its natural luster, emanates a distinctive formality unlike typical hilts wrapped in cloth or leather.

In any case, this form was unique to the Heian period and rapidly fell out of use after the Kamakura period. In the swords of samurai engaged in actual combat, the wooden hilt block structure became the mainstream due to considerations of practicality and ease of repair, and the hair-pin-shaped technique disappeared without being passed down. This is why this structure is not seen in contemporary Japanese swords.

Scientific analysis of extant pieces has pointed to the possibility that the iron in the hilt portion and blade portion may have been intentionally varied in carbon content. If the grip portion was composed of malleable low-carbon iron while the blade portion responsible for cutting was made of harder steel——with the material properties intentionally differentiated by location within a single integrated forged piece——this would indicate that Heian-period iron workers possessed metallurgical control beyond mere shaping.

Historical Positioning——The Intersection of Continental Culture and Japanese Originality

The Heian period when hair-pin-shaped large swords were created was an era in which Japanese culture was gradually moving away from the direct influence of continental (Tang) culture that had dominated the Nara period, and uniquely Japanese "national aesthetic culture" was beginning to develop. In sword craftsmanship as well, this period coincided with the transition from continental straight swords to Japanese swords with the distinctive curved form of "bent large swords."

The structure of hair-pin-shaped large swords finds no clear precedent in continental sword craftsmanship and can be said to be distinctly Japanese in conception. At the same time, it inherits aspects of the lineage of Nara-period decorative swords such as "black-lacquered large swords (kurogurushi-no-tachi)" and "adorned large swords (kazari-no-tachi)," being also a product of the process whereby ritual and costume-related sword culture was refined within Heian aristocratic society.

The Heian period was also an era of "regency rule (sekkan seiji)." The upper aristocracy centered on the Fujiwara clan treated swords less as weapons than as symbols of authority and prestige, and this cultural background provided the soil from which the refined openwork of hair-pin-shaped large swords emerged. This form, where aristocratic aesthetic sensibility intersected with craftsmen's skills, constitutes crucial historical evidence that Heian-period sword culture stood at the boundary between its continental past and its Japanese future.

Extant Representative Examples——Masterpieces Protected as National Treasures and Important Cultural Properties

Hair-pin-shaped large swords are extremely rare, with virtually all existing examples designated as either National Treasures or Important Cultural Properties. Due to their scarcity, each of the few extant examples is treated as primary source material in Japanese sword research.

The most widely known representative extant example is the "Tsurumarukumarukuninaga (鶴丸国永)." This large sword, held by the Imperial Household Agency, is said to be the work of Kuninaga, a swordsmith of the Gojo school. The Gojo school was a separate lineage from the Sanjo school (Munenaka) and represents a renowned group of craftsmen representing the old sword period. The Tsurumarukumarukuninaga is a rare surviving specimen where the hair-pin-shaped openwork of the hilt portion remains in perfect form, and both the overall aesthetic form and the blade pattern are highly regarded as representing the pinnacle of Heian-period sword beauty. Due to Imperial Household Agency management, public viewing opportunities are limited, but its elegant form can be confirmed through photographic materials and catalogs.

Among other extant examples, several swords have been transmitted to Kasuga Shrine in Nara, Shitennoji Temple in Osaka, and various shrines and temples throughout the country. Many of these have been preserved to the present day having escaped the secular warfare and fires that ravaged the country due to their history as long-term votive offerings to deities and Buddhas. The special preservation environment provided by shrines and temples can be said to be the greatest factor enabling the survival of hair-pin-shaped large swords.

Additionally, a hair-pin-shaped large sword is transmitted to the Atsuta Shrine treasure museum in Aichi, known as an example where refined patterns were applied not only to the openwork carving of the hilt but also to the tang. This provides a concrete example demonstrating that these were both functional swords and craft objects that appealed to the aesthetic sensibilities of Heian aristocracy. It is also noted that this hair-pin-shaped openwork design may have influenced the openwork decoration of later sword fittings——such as tsuba (cross-guards) and menuki (grip ornaments)——giving rise to perspectives that position hair-pin-shaped large swords not as isolated curiosities but as one source stream of Japanese sword ornament culture.

Appreciation Points——Elements to Observe in Original Works and Photographic Materials

While opportunities to actually appreciate hair-pin-shaped large swords are exceedingly rare within Japan, occurring perhaps only a few times per year at most, a deeper appreciation can be achieved by keeping in mind the key points to focus on when viewing these works in museum exhibitions or photographic materials.

The Shape and Precision of the Hilt's Openwork: The smoothness of the outline of the hair-pin-shaped opening and its bilateral symmetry directly demonstrate the craftsman's technical level. The fact that such precise openwork can be achieved in an integrated iron piece concentrates the high level of Heian-period iron-working technology. Those with clean edges of the opening, showing no roughness or distortion and finished with careful precision, are regarded as superior examples.

The Curve of the Blade and the Shape of the Point (Kissaki): As large swords from the late Heian period, many exhibit waist curve (koshi-zori) or inner curve (uchi-zori), differing from the middle and forward curves that became mainstream after the Kamakura period, possessing a unique "form (sugata)" characteristic of the Heian period. The point often displays what is called a "small point (kokissaki)"——a small rounded form——which is also a typical characteristic of Heian-period large swords.

The Grain Structure (Jigane) and Blade Pattern (Hamon): Many extant examples are difficult to observe due to extended preservation and repeated rusting and polishing, but in well-preserved examples, the calm, small-scale wood-grain-like structure (ko-itame-hada) characteristic of the old sword period can sometimes be confirmed, along with blade patterns showing fine straight-line temper (hoso-sugu-ha) or small irregular patterns (ko-midare).

Conclusion——A Form That Existed Only in the Heian Period, Never to Be Born Again

Hair-pin-shaped large swords are "singularities" in Japanese sword history. Never mass-produced, possessing no successors, they represent a unique form closed within the Heian period alone. That this style was not inherited after the Kamakura period, when samurai rose to prominence and practical swords were demanded, was historically inevitable.

Yet the handful of extant examples serve as irreplaceable witnesses to understanding the origins and diversity of Japanese swords. When given the opportunity to encounter original hair-pin-shaped large swords such as the Tsurumarukumarukuninaga, one should appreciate them not only for the beauty of the swords themselves but also holding in one's heart the question of what the craftsmen of the Heian period sought to invest in these blades. Beyond those openwork holes, the spirit of an age when martial prowess and beauty were undifferentiated still dwells.