Zanba-to (Horse-Slaying Sword): Structure, Battlefield Use, and Differences from Nodachi and Otachi

What is a Zanbatou?

The zanbatou is, as its name suggests, said to be an extremely large sword created for the purpose of "cutting horses." However, looking at the historical reality, this name has been used with multiple meanings, and there is not a fixed definition pointing to a single type of sword. In Japan, it is often used mainly as a collective term for swords with longer blade lengths than usual and greater cutting power.

It is a concept distinct from similarly-named weapons of Chinese origin (Chinese: zhanmadao or zhanmajian), and in Japan the zanbatou appears mainly in classical literature, military chronicles, and later martial arts texts. As for actual excavated items and existing cultural properties, distinction from nodachi and ōdachi is difficult, and classification often differs among researchers.

Differences Between Nodachi and Ōdachi

To understand the concept of zanbatou, it is first necessary to clarify the differences between nodachi and ōdachi.

Ōdachi refers to tachi with blade lengths of 90 cm or more (3 shaku or longer), and most were created as offerings to shrines and temples or for ceremonial purposes. Most existing ōdachi are "hōnō ōdachi" (donated ōdachi) and were not intended for actual combat use. It is not uncommon for weight to exceed 5 kg, and it is difficult for an ordinary person to handle freely with one hand.

Nodachi refers to ōdachi that were actually used (or usable) on the battlefield. They are said to have been carried to the battlefield on the back and used in a manner similar to long-handled weapons to sweep away enemies. Blade lengths are often around 60–90 cm, not as extremely large as ōdachi, but much longer than ordinary uchidachi or tachi.

Zanbatou are often used as further enlarged or specialized variations of nodachi, or in a manner nearly synonymous with nodachi. They are generally described with the nuance of a large, heavy sword capable of severing a horse's legs or torso in a single blow.

Structural Features

The following structural features are common to zanbatou, nodachi, and ōdachi.

Blade length greatly exceeds that of ordinary tachi (around 60–75 cm). While blade lengths of 90 cm or more are the standard for ōdachi, many nodachi said to have been used practically are around 70–90 cm. Long blade lengths create a wider "ma-ai" (distance interval) to reach opponents from afar, but simultaneously result in increased weight and reduced maneuverability.

Sori (blade curvature) tends to be shallower compared to ordinary tachi. For wielding a long blade downward from horseback, a shallower sori is said to be easier to handle than a deeper one. On the other hand, when intended for use on foot (kachi), the sori shape affects practicality.

Tsuka (hilt) length is also longer than ordinary swords and is premised on being held with both hands. In some cases, they are said to have been fitted to hafts of 3 shaku (approximately 90 cm) or longer and used like naginata.

Actual Use on the Battlefield

As for how zanbatou and nodachi were actually used on the battlefield, descriptions in historical documents and later legends are intermingled, making it difficult to clarify the actual circumstances.

In textual descriptions, many scenes depict foot soldiers (kachi-musha) carrying nodachi playing active roles in battles during the Nanboku-chō period (14th century). The Nanboku-chō period was particularly an era when the proportion of infantry units increased, and it is believed that tactics of mowing down multiple enemies with long swords were effective.

As for use against horses, considering the combat style of the era, it is inferred that the primary use was attacking horses in group combat rather than opposing mounted samurai one-on-one. Tactics are described in which slashing a horse's legs would cause a mounted samurai to fall, and they would then be finished off in grappling (kumi-uchi). However, severing a horse's legs reliably required considerable skill and stamina, and was not a weapon easily used by ordinary soldiers.

Relationship to Existing Swords

Currently, most large swords housed in museums and at shrines and temples have the character of "hōnō tachi" (donated tachi) and the majority show no traces of actual combat use. On the other hand, the existence of nodachi showing traces of chipping and signs of use has been confirmed, indicating that practical examples of battlefield use did exist.

Notable examples include large groups of donated swords housed in the Bizen Sword Museum in Okayama Prefecture and various shrines throughout the country. There are also ōdachi designated as National Treasures or Important Cultural Properties, demonstrating the high level of forging technology of the era.

Contemporary Perception of Zanbatou

In modern times, the term "zanbatou" has become widely used in popular culture such as games, novels, and films. It often circulates connected to images of fantasy-like giant swords, and in some aspects an image far removed from historical reality has become established.

Among sword enthusiasts and researchers, it is considered important to distinguish between the actual history of ōdachi and nodachi and the modern image of "zanbatou." To accurately evaluate the historical and artistic value held by large swords as cultural properties, careful cross-referencing of textual and physical evidence is indispensable.