Bajo-zashi (Cavalry Short Sword) — Structure, Use, and Morphological Features of the Mounted Warrior Short Blade

What is Bashouza? – The Self-Defense Blade of Mounted Samurai

"Bashouza" (basyouza) is a type of short blade (tanto) or secondary sword (wakizashi) designed and used primarily for combat on horseback. It is a sword specialized in blade length, curve, and weight balance to enable a mounted warrior to draw it instantly while manipulating reins with both hands, featuring a unique design philosophy distinct from ordinary tantos or wakizashis.

In close combat on horseback, two phases were envisioned: "slashing while mounted" (bashou-giri), striking without dismounting, and "self-defense after dismounting," transitioning to hand-to-hand combat after falling from the horse. The bashouza was designed to handle both scenarios and became established as equipment for warriors prioritizing mobility, particularly from the late Kamakura period through the Nanboku-cho period.

Tachi and Uchigatana – Basics of Mounted Sword-Wearing

To understand the bashouza, one must first grasp the differences between the wearing methods of the tachi and uchigatana.

• Tachi: Carried in the haitou style, suspended from the waist belt with the edge facing downward. This method was suited for drawing while mounted and was the standard equipment of mounted samurai from the late Heian period through the Kamakura period. The tachi blade frequently featured a shape called koshizori (waist curve), where the peak of the curve appears near the handle, facilitating the coordination of the drawing motion and the downward swing of the blade while mounted.
• Uchigatana: A method of inserting the blade upward into the waist belt, excelling at quick drawing (iaijutsu) primarily in foot combat. Since the scabbard tip could strike the horse's rear and startle it, this style was considered unsuitable for mounted use.

The bashouza is a form derived from the tachi-wearing tradition, providing self-defense while mounted in a more compact size than the tachi.

Metezashi and Yundezashi – Left and Right Placement

Specialist terminology exists for the left and right positioning of blades when worn by warriors on horseback.

• Metezashi: A method of wearing the blade on the right side, on the mete (right hand) side. Positioned opposite to the usual left-side placement, it offered the advantage of immediate drawing with the right hand, though historical records of this practice are limited.
• Yundezashi: The common method of wearing on the yunde (left hand) side, that is, at the usual left waist. When mounted archers drew the bow with the right hand, the blade at the left waist would not impede the hand's movement.

Formal Characteristics – Blade Form and Curve Design

The blade length of the bashouza generally falls in the range of 30-60 cm, slightly longer than the tanto (less than one shaku) and typically within the shorter range of the wakizashi (less than two shaku). The most prominent formal characteristic is the emphasis on the koshizori (waist curve). While ordinary uchigatanas and tachis typically have the peak of their curve near the center of the blade, bashouza most often feature a koshizori-type curve with the maximum point near the blade junction, facilitating the coordination of drawing and downward swinging from horseback.

The blade thickness (kasane) is relatively substantial, with high lateral rigidity. This design was intended to withstand impact from falling or grappling, displaying practical orientation in contrast to the slender, finely polished ceremonial blades. The blade width is narrow, giving an overall slender impression, though the weight tends to be slightly heavier compared to same-length blades.

Characteristics of the Koshirae – Optimization for Mounted Use

The koshirae (fittings) of the bashouza show adaptations throughout, specially tailored for mounted use. Regarding how it was worn, while ordinary wakizashis were inserted into the belt and fixed at the waist, the bashouza was sometimes carried suspended from the waist belt in the haitou style or attached to the saddle. This allowed quick access to the hilt even while manipulating reins.

• Tsuka (grip): Often kept short, optimized for single-handed drawing and downward striking.
• Tsuba (crossguard): Relatively small, designed to prevent snagging during mounted swinging motions.
• Koiguchi (scabbard mouth): Sometimes made loosely fitting, prioritizing swift drawing.

The Development of Bashouza in the Kamakura and Nanboku-cho Periods

The bashouza achieved its greatest cultural and practical significance from the late Kamakura period through the Nanboku-cho period (14th century). During this time, samurai combat evolved from group mounted archery tactics to close-range slashing engagement, transitioning from relying solely on the tachi to a system of using multiple swords. The bashouza served as a backup weapon in emergency situations when the tachi could not be used, and as a finishing blade after grappling. The phrase "with a small blade (kokatana) thrust at the waist" appears frequently in military chronicles of the Nanboku-cho period, and it is believed these often refer to bashouza-type short blades.

Changes After the Muromachi Period – From Practical to Ceremonial Use

With the onset of the Sengoku period, infantry combat centered on ashigaru (foot soldiers) became predominant, and the morphological advantages unique to the bashouza declined relatively. However, it remained important as equipment for mounted samurai of warlord and daimyo rank, leading to the emergence of the ornate "ceremonial bashouza." With the onset of the Edo period and the loss of practical combat opportunities, the bashouza came to be positioned within the unified aesthetic of mounted dress and survived as a decorative blade for samurai ceremonial occasions. Most extant bashouza from the modern era reflect this Edo-period ceremonial style and are typically preserved in their complete fitting configuration in museums and private collections.