Great Sword <Kazuzo>

A Sword With a Cord-Hole, Caught Between Two Ages

At the very end of the tang sits a single six-sided hole, drilled long ago to take a leather cord. On the straight swords carried by the Nara court, that cord-hole, the tenuki-o ana, was standard fitting. By the time the curved warrior's sword reached its mature form, the feature had disappeared. This blade still keeps it, and that one small detail fixes the weapon at a hinge point in the long history of the Japanese sword.

The Agency for Cultural Affairs records it plainly: a tachi made in shinogi-zukuri, one blade, an Important Cultural Property held by a private owner in Fukushima Prefecture and assigned to the Heian period (794 to 1185). No smith's name survives, and no exact year. What the sword carries instead is a body that belongs half to the ancient world of the straight blade and half to the curved sword that the rising warrior class would soon claim as its own.

Even the writing of the name marks the change. It is set down with the older character for "great sword," dai-to, rather than the character used for the later curved tachi. The shift in how the word was written tracks the shift in the weapon itself.

Why It Was Designated

The blade became an Important Cultural Property on 12 June 1989. The case for it rests less on beauty alone than on position. Around Nara, the older long swords were built in kiriha-zukuri, a flat-sided construction with the cutting bevel set off near the edge, and they were essentially straight. From the middle of the Heian period onward came the ridge-lined, gently curved blades now called Japanese swords. This tachi sits in the gap between those two families, showing in a single object how one form gave way to the other.

That lineage can be checked against the oldest swords in the country. Among the eighth-century treasures kept in the Shoso-in repository at Nara, one surviving blade is close to this one in form, and three more share the related kiriha-zukuri shape with a rounded point. Placed beside those imperial pieces, the Fukushima sword reads as a later, evolving cousin: still archaic in several respects, yet already reaching toward the silhouette of the medieval warrior's blade.

What to Look For in the Blade

The body is broad. The shinogi, the raised ridge that runs the length of the blade, sits near the center rather than high toward the back, a placement typical of these early ridge-line swords. The back itself is rounded, a maru-mune, where the mature Japanese sword would later settle on a crisp peaked spine. The point has no yokote, the small transverse line that normally divides the tip from the body, and it swells into a soft, rounded curve. The curvature through the whole blade is shallow, the first hint of the deep arc to come.

Near the base, in the flat of the blade, a small hole has been pierced and filled with copper inlay. The forging shows a large flowing wood-grain pattern that straightens into masame, a fine parallel grain, toward the edge, with patches of darker steel mixed through. From the hardened edge upward rises a faint, cloudy reflection in the steel, a shirake midare-utsuri that catches the light when the blade is turned.

The temper line is the part a sword specialist lingers over. It runs as a straight suguha, but at intervals the smith deliberately dipped it into small valleys and fed slender streaks of activity down toward the edge. Fine crystalline particles cluster along the line, and here and there run thin sweeps of sunagashi and bright lines of kinsuji. That worked variation, set into an otherwise plain straight temper, is read as an early sign of conscious artistry. The smith was no longer only making a tool. He was shaping how the steel would look.

Seeing Blades of This Kind

This sword is privately owned and is not on public display, so a visit to see it is not possible. Anyone drawn to the moment it represents, the passage from straight sword to curved Japanese blade, can find that story told well in a handful of public collections.

The Tokyo National Museum in Ueno holds one of the strongest sword collections in Japan, including ancient straight swords and the earliest curved blades, and rotates them through its galleries. The Japanese Sword Museum in the Ryogoku district of Tokyo, run by the society for the preservation of the Japanese sword, is built entirely around blade appreciation and is the best place to learn how to read forging and temper. For the ancestors of this tachi, the Nara National Museum stages an exhibition of Shoso-in treasures each autumn, when court objects of the eighth century, swords among them, are shown for a few weeks only.