Studying Sugata (姿, Blade Shape)

The overall shape (sugata) of a Japanese sword is the first big clue to its identity. Swords evolved in form over the centuries, responding to changes in warfare, armor, and fashion. An experienced collector can often place a blade within a general timeframe by its silhouette alone. When assessing sugata, consider the sword’s length, curvature, blade width (mihaba), thickness (kasane), profile (taper or funbari), the shape of the point (kissaki), and the shape of the tang (nakago). These attributes, taken together, are strongly indicative of certain periods and schools.

Heian to early Kamakura (10th–12th centuries): The earliest true nihontō (as opposed to straight ancient swords) were long tachi meant for cavalry combat. A typical late Heian blade is very long (around 30 inches or more) with elegant deep curvature concentrated near the base (koshi-zori)​. They are usually narrow with a noticeable taper from the base to the point (strong funbari) and have a small kissaki (ko-kissaki). These graceful blades were effective for slashing from horseback. Many Heian blades surviving today have been heavily polished down and even shortened over time; one often finds their hamon very faint or the kissaki reshaped due to centuries of polish​. Collectors accept a degree of wear in such ancient blades given their rarity. Early Kamakura blades (late 12th to early 13th century) continue this style initially, but as armor improved, swords began to beef up.

Mid to Late Kamakura (13th century): By the mid-Kamakura period, tachi became broader and less tapered to better deal with armor​. The deepest point of curvature moved up to the middle of the blade (tori-zori), rather than just at the base. We also see the emergence of the ikubi-kissaki (“boar’s neck” snub-nosed tip) in some mid-Kamakura blades​ – these are stout short kissaki that appear almost blunt, a design believed to prevent the tip from snapping against armor. By late Kamakura (early 14th century), many swords had a moderate curve, slightly shorter length (perhaps 26–28 inches), a bit less taper, and a medium-sized point (chu-kissaki)​. This shape – with chu-kissaki, moderate funbari, and tori-zori – became a very balanced and common style that would carry into the next period. Famous schools like the Ichimonji (Bizen) at this time made some flamboyant shapes: very wide blades with elegant curve and large kissaki for their 13th-century masterpieces.

Nanbokuchō (mid 14th century): This period saw some of the most extreme sword shapes. Blades grew huge in both length and width, some exceeding 90 cm in nagasa (blade length). Many 14th-century 𝑛𝑒𝑛𝑝𝑦𝑒𝑡 swords were made almost as ōdachi (great swords). A hallmark of Nanbokuchō is blades that are very wide at the base with little or no taper (sometimes almost the same width at tip), relatively thin in thickness, with a shallow curvature and a massive kissaki (o-kissaki). The overall impression is a grand, broad weapon – reflecting the fierce warfare of the period. Such swords often had to be shortened in later eras to be practical (many surviving ones are ō-suriage mumei now). It’s breathtaking to encounter an ubu (unshortened) Nanbokuchō blade – their dimensions are unlike any other period. This era also produced many hira-zukuri no-kissaki blades (especially long tanto or ko-dachi without ridgeline) as diversifications of style​

Muromachi (15th–16th centuries): Early Muromachi still saw some large tachi, but a major shift occurred mid-century: the rise of the uchigatana. As warfare tactics transitioned from cavalry to infantry foot soldiers, excessively long swords became impractical​​. The uchigatana was a shorter sword (often 60–70 cm) worn at the waist, edge up, which could be drawn and struck in one motion. Many earlier long tachi were cut down to uchigatana length around this time (hence the term suriage tachi). A typical Muromachi katana (especially late 15th century) is around 70 cm (27–28 inches) long, has a more modest curvature (often with a bit of saki-zori, meaning the deepest part of curve is toward the tip)​, and has a chu-kissaki. The blade is not as wide at the base as Nanbokuchō pieces, and there is less taper (funbari) than Kamakura ones – a fairly straight profile overall. Late Muromachi (16th c. Sengoku era) saw a lot of utilitarian weapons: many blades became somewhat wider and thicker again, with slightly larger kissaki, to serve in the brutal battlefield conditions​. However, because styles varied by region, one also finds slender, elegant swords still being made in the 1500s in certain schools. Generally, though, a mid-16th century sword can look similar to a late-Kamakura piece but usually with less graceful curvature and a more robust build. Also, the practice of using two hands was fully adopted by this time, influencing sword length and balance​

Edo Period / Shintō (17th–18th centuries): With the establishment of peace under the Tokugawa shogunate (early 1600s), swords evolved again. During the early Edo, since there were fewer real battles, the sword became less of a purely military weapon and more a status symbol and art object (though still fully functional). The Kanbun era (c. 1660s) style is well known: these katana have a very shallow curvature (almost straight), are a bit shorter on average (around Katana ~ 26–28 inches), and have a stout build with a Chu-kissaki​. Kanbun Shintō blades often look straight when worn, a drastic change from the elegant curves of earlier times – this is thought to reflect a revival of interest in the simpler forms and perhaps influence from straight Chinese sabers. As the Edo period progressed, swordsmiths in different regions developed their own preferences, but many Shintō blades share traits: a consistent curvature (not too deep), often tapering very little from base to tip (giving a robust feeling), a medium kissaki, and clean lines. Because polish and aesthetics became very important, Shintō blades are often perfectly symmetric in shape and without the wild dimensions of Koto blades. By the late Edo (18th–19th century), some smiths began copying Kamakura or Nanbokuchō shapes as part of a fukko (revival) movement – so you might find a late Edo katana that is extremely wide with an enormous kissaki, imitating a 14th-century style. But generally, most Edo-period katana have what we consider the “classic samurai sword” look: around 70 cm, gentle curvature, balanced proportions. It was noted that in the late 1700s some swords were made more for display – extremely flamboyant hamon, excessive carvings – as the sword was by then less a combat tool. This is sometimes referred to as a period of decadence for sword art, but many masterpieces were still made.

Shinshintō (Late 18th–19th centuries): The late Edo revival brought back many old shapes. Swordsmiths like Suishinshi Masahide spearheaded a return to Koto aesthetics​. Thus, a Shinshintō sword might deliberately emulate a Kamakura tachi (with koshizori and ko-kissaki) or a Nambokuchō style (ō-kissaki and wide mihaba) or any other classical style. This makes shape analysis trickier – a blade made in 1850 could look like one from 1350. However, Shinshintō pieces tend to be very heavy in construction (thick kasane), often with less distal taper. If you hold one, it may feel more top-heavy or hefty than an antique of similar shape. Many are also flawlessly preserved (since they are newer), whereas true Kamakura pieces usually show some age and wear. Shinshintō tangs will have signatures and dates of the 1800s, of course, which clarifies matters if present. The key for the advanced collector is to use sugata in combination with nakago examination to tell revival work from genuine Muromachi or Kamakura work.

While shape is primarily dictated by era, certain schools had nuances. For example, the Bizen Osafune school in the 14th–15th century favored graceful koshizori and sometimes slightly longer kissaki; the Mino school in late Muromachi made many swords with slightly straighter shape and pointed togari (pointed) boshi, etc. Learning these subtleties can further narrow down origin. But as a foundation, always place the sword in its chronological context first by sugata. Is it slender and deeply curved? Likely Kamakura. Thick and straight? Perhaps Kanbun Shintō. Long and broad with shallow sori? Nanbokuchō or a revival of it. Short and utilitarian? Late Muromachi. This thought process is fundamental in kantei.

Don’t forget to inspect the nakago (tang) as part of sugata. The tang shape and condition give away both age and sometimes school. Very old Koto swords often have tangs that are dark blackish with centuries of patina, and the tang may have been greatly shortened (ō-suriage, losing its original shape). Most shortened tangs will end in a straight cut across (kiri nakago-jiri)​, since the polisher simply cut the metal. In contrast, an original ubu tang might have a specific shape filed: common tang-end shapes include kurijiri (rounded like the end of a chestnut), ha-agari (angle cut with the ha side higher), kengyō (pointed symmetrical), iryamagata (asymmetrical peak), etc. For example, the Sōshū tradition often shows a kurijiri tang end, while many Shintō Edo smiths used kengyō. If you see a tang that is cut flat, especially with the patina appearing evenly old on the cut, it’s likely the blade was shortened long ago (common for early blades to be cut down in later periods)​. Also examine the yasurime (file marks) on the tang. Different schools had preferred tang filing patterns – sujikai (diagonal down towards tip) and ō-sujikai (steeper diagonal) are often seen on Kamakura/Nambokuchō blades and many Edo blades; kiri-yasuri (horizontal file marks) are typical on some Koto Bizen and Shinto Osaka works; katte-agari (slanting up) vs katte-sagari (slanting down) are variations used by certain smith lineages; higaki (cross-hatched “chrysanthemum” file marks) famously appears on some Yamato Shizu blades and Satsuma swords​. Advanced collectors use tang shape and yasurime as additional kantei points. Of course, the presence of a mei (signature) on the tang can be the most direct clue – but as we’ll discuss, mei require careful scrutiny for authenticity.

In summary, take a step back and view the sword’s silhouette and tang before getting lost in the minutiae. The sugata is like the sword’s “body language” – it will often tell you the time period and sometimes the region. Comparing the sword in hand to known reference examples from books or museum collections (many of which illustrate typical shapes of each era​) is extremely useful. With practice, you’ll immediately recognize a Kamakura tachi versus an Edo katana simply by their stance. Sugata is arguably the most important factor in kantei – it sets the stage for all other observations​. Always judge shape first, then move on to the finer details.