If any single weapon defines Japanese military culture in the global imagination, it is the sword. The Japanese tradition produced blades of remarkable technical sophistication — folded-steel construction, differential heat treatment, individual smith signatures — and produced them in volumes and across centuries that gave the form room to evolve. The four entries below trace that evolution: the older curved cavalry tachi, the iconic katana that replaced it, the wakizashi worn paired with the katana, and the tantō dagger that completed the samurai's kit.
Tachi
The older of Japan's two great curved swords. The tachi developed during the Heian period (794–1185) as the primary cutting weapon of the mounted samurai, and remained dominant through the Kamakura period and into the early Muromachi (roughly 900 to 1400). It was carried slung edge-down from the belt, hung from cords on the scabbard rather than thrust through it — a horseman's mode of carry, designed for drawing and cutting from the saddle.
Tachi blades were typically longer and more curved than later katanas, with the deepest curve set further toward the hilt. Surviving Kamakura-period tachi from master smiths like Masamune are among the most revered objects in Japanese metalwork. As foot combat displaced cavalry combat in the late Muromachi and Sengoku periods, the tachi was eclipsed by the shorter, edge-up katana — and many fine tachi were physically shortened (a process called suriage) to be remounted as katanas, which is why surviving signed tachi blades are scarcer than the original numbers would suggest.
Katana
The iconic curved sword of the samurai. The katana emerged in the late Muromachi period (15th century) and reached its mature form during the Sengoku wars of the 16th century. Slightly shorter and less curved than the tachi it replaced, the katana was worn through the obi (belt sash) edge-up rather than slung edge-down — a small change in carry that allowed a single fluid motion of draw-and-cut, the technique that became the basis of the Japanese sword art.
The katana is famous less for its battlefield role — on a Sengoku battlefield, the spear and bow killed more men than swords did — than for its technical refinement and its symbolic position. Made of folded laminated steel with a hard cutting edge differentially tempered against a softer springy core, the katana represented the high point of Japanese metallurgy. After the Tokugawa peace ended large-scale war, the katana persisted as the symbol of samurai status, paired with the wakizashi as the daishō ("big-little") that only samurai were legally permitted to wear.
Wakizashi
The shorter companion sword to the katana. With a blade of roughly twelve to twenty-four inches, the wakizashi was the second half of the daishō — the paired set that defined samurai status under the Tokugawa shogunate. Where the katana was a battlefield weapon and an outdoor weapon, the wakizashi was for indoor use: the shorter blade was practical in the cramped rooms of a Japanese house, and samurai were expected to surrender their katana when entering another's residence but could keep the wakizashi.
The wakizashi served as a backup if the katana was lost or broken, as a parrying weapon in two-sword (nitō) styles, and — in the most ritualized use — as the blade for seppuku, the formal warrior suicide. It was, in effect, the sword a samurai always had with him: removed only for sleeping, never surrendered, the constant material symbol of the warrior's status and obligations.
Tantō
The samurai's dagger. Under twelve inches in blade length, sometimes pointed and sometimes blunt-tipped depending on style, the tantō rounded out the samurai's blade kit. Its origins are old — tantō-form daggers appear in Heian-period contexts — and its uses were various: a last-resort close-combat weapon, an armor-piercing thrusting blade in the grappling phase of armored fighting, a tool for the everyday cutting work of samurai life, and a ceremonial object.
Tantō were made by the same master smiths who made tachi and katana, and surviving examples in good condition are art-historically significant in their own right. The tantō also has a specific role in the ritual of seppuku — a small white-handled tantō was the traditional implement for the actual cut, with the wakizashi serving as the larger backup. The form persisted long after the samurai era ended; modern Japanese sword culture continues to make and study tantō.