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

Fundamentals of Japanese Sword Polishing—Traditional Processes and the Craftsman's Pride

Japanese sword polishing is broadly divided into two main stages: "rough polishing" and "finish polishing."

Rough polishing starts with coarse whetstones and gradually progresses through medium and fine whetstones, removing irregularities in the blade steel and surface texture while establishing the sword's shape. At this stage, the polisher confirms the balance of the blade's curvature, point width, and root width, correcting any distortions from the forging process while exposing the surface texture. It is at this stage that differences in the polisher's skill become most apparent.

Finish polishing employs natural whetstones in a precise process to bring out the maximum beauty of the surface texture and blade pattern. Ultra-fine whetstones such as nagura-do and uchigumori-do are used, along with harii—minute polishing using small stone fragments attached to fingertips. Particularly in the process of "edge-defining," which accentuates the hamon, the pattern line from hamachi to kissaki is carefully brought out stroke by stroke. The techniques employed at this stage vary subtly among different schools, and each tradition—such as Honami-school or Yamashiro lineage polishing—preserves secret methods passed down through generations.

Traditional polishers made it their paramount principle to "bring out the most beautiful form of each sword," meticulously planning their approach according to the sword's individual character—the hamon's distinctive features, the surface texture's qualities, and the steel's origin. Time spent on a single sword could span from weeks to months, making the polisher's work closer to that of an artist than mere craftsmanship.

The Impact of Showa-Era Military Sword Demand on the Polisher Industry

The sharp increase in military sword demand from the early Showa era through the Pacific War fundamentally transformed the structure of the polisher industry.

Army officers of that time were all required to carry military swords, and as the war expanded, demand grew exponentially. In 1939 (Showa 14), the "Army Commissioned Swordsmith System" was established, permitting only swordsmiths of a certain standard and above to forge military swords; however, even the production of regularly forged blades could not keep pace with demand.

To meet this excess demand, industrial military swords called "Showa-to" appeared. Mass-produced at factories such as Tokyo Gas Electric Industries (later Tokyo Gas Electric Co., Ltd.), these swords were manufactured from uniformly machined steel, possessing a fundamentally different material and structure from traditional swords forged with tamahagane and fold-forging techniques.

With polishing demand vastly exceeding the number of available polishers, "practical polishing"—a lower standard than traditional artistic polishing—became widespread, and speed-prioritized finishing was standardized. Even experienced polishers had to complete multiple swords daily, and "skip polishing," which reduced the number of whetstone stages, became rampant. This practice left fine polishing marks on the sword surface, a method nearly forbidden in true artistic polishing, yet wartime conditions forced such compromises.

Confronting Industrial Swords—The Material Challenge Facing Polishers

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

Tamahagane possesses jihada—a surface texture created by uneven carbon content. The characteristic patterns of itame, mokume, and masame gradually emerge as polishing progresses. The polisher reads this response and adjusts the pressure, angle, and whetstone selection accordingly.

In contrast, industrial Showa-to steel has uniform carbon content and lacks jihada. Without the layers created by fold-forging, the hamon appears merely as a uniform wave pattern from heat-treatment, lacking the complex variations in nie and nioi within the blade that characterize traditional swords.

A further problem lay in the hardness characteristics of industrial steel. Industrial swords with uniform heat-treatment had high surface hardness, yet fine scratches remained easily during polishing and readily clogged the pores of natural whetstones. Some polishers developed a technique of "creating patterns through polishing" on industrial sword surfaces to artificially produce the appearance of hamon, but this cannot be said to be anything other than a convenient method deviating from the proper path of sword polishing.

Securing whetstones was also a grave problem. High-quality natural whetstones—particularly uchigumori-do from Kameoka, Kyoto—had become scarce since wartime, and as military supplies took priority in procurement, distribution to polishers was severely strained. The situation forced the use of inferior substitute whetstones, leading to further degradation of polishing quality.

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

Military sword polishing in the Showa era clearly differentiated into two standards based on the client's position and purpose.

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

Contemporary Restoration Polishing of Showa Military Swords—New Challenges Facing Polishers

Many Showa military swords currently in existence and circulation have accumulated rust, corrosion, and polishing damage from prolonged storage and poor maintenance. Restoration polishing to address these issues has become one of the important responsibilities of modern polishers.

• Rust-removal polishing can address light rust through polishing with coarse whetstones. However, deep pit rust (tensabi) is embedded in the steel itself, so removing it inevitably means deleting a portion of the blade. Progress must be made with careful judgment regarding impact on the remaining hamon; attempting to forcibly remove rust at the cost of destroying the blade pattern defeats the purpose.

• Artistic restoration polishing of traditionally forged swords demands traditional artistic polishing techniques for restoration of valuable Showa swords such as Yasukuni blades or works by commissioned swordsmiths. As of 2026, the market estimate is approximately 500,000 to 2,000,000 yen per sword, though cost varies greatly depending on the sword's condition, the polisher's skill, and the depth of polishing required. When surface damage is extensive, rough polishing alone can require several months.

• Regarding industrial swords, investing in high-cost artistic polishing for low-value mass-produced Showa swords is not economically rational. For such swords, practical polishing using modern whetstones and tools is often sufficient.

When considering restoration polishing, it is essential to first confirm the sword's condition through a specialist (a polisher or sword merchant) and verify the sword's provenance and the presence of authentication documents before establishing a polishing plan. The value of Showa military swords varies greatly from piece to piece, and the preconception that "military swords have little value" must be avoided. Through appropriate polishing and preservation, a single sword that survived the turbulent Showa era can continue to convey its value as historical testimony to future generations.

For details on the polishing process itself, see the related column The Polisher's Work; for the lineage of contemporary swordsmiths working with tamahagane, refer as well to Contemporary Swordsmith Styles.