Military Sword Polishing: The Challenges Facing Showa-Era Polishers Working with Both Industrial and Traditional Blades

The Fundamentals of Japanese Sword Polishing—Traditional Processes and the Pride of the Polisher

Japanese sword polishing is broadly divided into two stages: "undercoat polishing (shitaji-togi)" and "finishing polishing (shiage-togi)."

Shitaji-togi begins with coarse stones (arado) and gradually progresses through medium stones (nakado) and laying stones (shikido) to finer whetstones, removing irregularities from the blade steel and ji-hada while refining the sword's shape (katana-sugata). Here, the polisher confirms the balance of the sword's curve (sori), tip width, and root width, exposing the ji-hada while correcting distortions that arose during the forging stage. At this stage, differences in the polisher's skill become most apparent.

Shiage-togi uses natural whetstones to perform precise work that brings out the beauty of the ji-hada and hamon to the fullest. Ultra-fine whetstones such as nagura-do and uchi-gumori-do are used along with hari (small pieces of whetstone attached to the fingertips) for extremely fine polishing. In particular, the "hadori" (blade-revealing) process carefully brings out the hamon line from the hamachi to the kissaki one strand at a time. The techniques at this stage vary subtly by school, with each tradition preserving secret methods such as Honami-style and Yamashiro-tradition polishing.

Traditional polishers made it their supreme goal to "polish each sword to reveal its most beautiful form," carefully developing polishing plans tailored to the sword's individuality—the characteristics of its hamon, the nature of its ji-hada, and the origin of its steel. The time spent on a single sword could stretch from weeks to months, making the polisher's work closer to that of an artist than a craftsman.

The Impact of Showa-era Military Sword Demand on the Polishing Industry

The sharp increase in military sword demand from the early Showa period through the Pacific War transformed the structure of the polishing industry itself.

Army officers at the time were all obligated to wear military swords, and as the front lines expanded, demand grew exponentially. In 1939 (Showa 14), the "Army Appointment Sword Smith System" was established, allowing only sword smiths of a certain standard to forge military swords, but even so, the production of properly forged swords could not keep up with demand.

To meet this excess demand, industrial military swords called "Showa-to" appeared. These swords, mass-produced in factories such as Tokyo Gas Electric Works (later Tokyo Gas Electric Corporation), were manufactured from uniformly forged steel and possessed fundamentally different materials and structures from traditional tamahagane folded-forging techniques.

As polishing demand overwhelmingly exceeded the number of available polishers, "practical polishing (jitsuyou-togi)" emerged, which lowered the standards of traditional artistic polishing, and speed-prioritized finishing became standard. Even skilled polishers had to work on multiple swords per day, and "skip polishing"—using fewer whetstone stages—became widespread. This practice left fine polishing scratches on the blade surface and was nearly a forbidden technique by traditional artistic polishing standards, but wartime reality forced such compromises.

The Struggle with Industrial Swords—The Material Challenges Facing Polishers

Traditional tamahagane swords and industrial Showa-to behaved completely differently under polishing. This difference became the greatest technical challenge for Showa-era polishers.

Tamahagane possesses ji-hada created by uneven carbon distribution. Distinctive patterns such as itame, mokume, and masame have the property of gradually emerging as polishing progresses. Polishers adjusted the pressure, angle, and whetstone selection by reading these reactions.

In contrast, industrial Showa-to steel has uniform carbon content and lacks ji-hada. Without the layers created by folded forging, the hamon appeared merely as a uniform wave pattern from the heat treatment, lacking the complex beauty (keshiki) of traditional swords—the nie and nioi within the blade.

Additionally problematic was the hardness characteristics of industrial steel. Industrial swords with uniform heat treatment had high surface hardness but easily retained fine scratches during polishing and easily clogged the pores of natural whetstones. Some polishers developed techniques to artificially create the appearance of hamon-like patterns on industrial swords through polishing, but this must be considered a shortcut that deviated from the true path of sword polishing.

Sourcing whetstones was also a serious problem. High-quality natural whetstones—particularly uchi-gumori-do from Kyoto's Kameoka region—had been scarce since the war, and as military supplies took priority, the supply to polishers became severely constrained. Polishers were forced to use inferior substitute whetstones, leading to further declines in polishing quality.

"Military Polishing" and "Artistic Polishing"—Coexistence of Two Standards

Showa-era military sword polishing clearly bifurcated into two standards depending on the patron's status and purpose.

Military polishing was practical polishing that prioritized blade sharpening (ensuring cutting ability). The finishing of ji-hada and hamon aesthetics was omitted or greatly simplified, and the number of whetstone stages was kept to a minimum. This standard prioritized battlefield practicality—that the blade wouldn't chip, wouldn't rust easily, and would fit well in the scabbard—over the blade's visual beauty as a sword.

Artistic polishing was polishing of the same standard as traditional art swords, commissioned by officers as personal orders. Masterworks by appointed sword smiths and Yasukuni-forged swords (swords forged in the sword hall within the Yasukuni Shrine grounds) often received artistic polishing. Polishing of Yasukuni swords by renowned polishers shows meticulous differentiation of whetstones and careful attention to fine details such as chikei and kinsuji within the blade. Costs and time were several to ten times those of military polishing.

This coexistence of two standards illustrates that within the category of "military sword," there existed an extremely broad spectrum ranging from mass-produced industrial goods to the pinnacle of traditional craftsmanship.

Modern Showa Military Sword Restoration Polishing—New Challenges Facing Contemporary Polishers

Today, many Showa-era military swords remaining and circulating throughout the country have accumulated rust, corrosion, and polishing damage from long-term storage and poor maintenance. Polishing work to restore these swords has become one of the important tasks facing modern polishers.

In rust-removal polishing, light rust can be removed by polishing from coarse stones. However, deep pitting rust (tensabi) eats into the sword steel itself, so removing it necessarily means removing part of the blade. Progress must be made while carefully assessing the impact on the remaining hamon, as destroying the hamon in an overzealous attempt to remove rust would be counterproductive.

In artistic restoration polishing of traditionally forged swords, traditional artistic polishing techniques are required for restoring valuable Showa swords such as Yasukuni swords and works by appointed sword smiths. As of 2026, the market estimate is approximately 500,000 to 2,000,000 yen per sword, though costs vary significantly depending on the sword's condition, the polisher's skill, and the depth of polishing required. In cases of significant ji-hada damage, just the undercoat polishing alone can take several months.

Regarding industrial swords, investing significant funds in artistic polishing for mass-produced Showa swords with low artistic value is not economically rational. Many such swords are adequately served by practical polishing using modern whetstones and tools.

When considering restoration polishing, it is essential to first confirm the sword's condition through an expert (a polisher or sword dealer), verify its provenance and whether a certificate of authenticity exists, and then develop a polishing plan. The value of Showa military swords varies greatly from piece to piece, and the preconception that "military swords have low value" should be avoided. Through proper polishing and preservation, a single sword that survived the turbulent Showa era can continue to transmit its value as historical testimony to future generations. Please also refer to related articles on Japanese sword polishing and care.