The Kyotoku War (1455–1483) and Sword Culture: How 28 Years of Kanto Conflict Fostered Regional Swordsmiths and Mass-Produced Blade Demand

What Was the Kyotoku Rebellion? — The Decline of Muromachi Shogunate Authority and the Great Kanto Uprising

The Kyotoku Rebellion (Kyotoku no ran) was a large-scale conflict that began in 1454 (the third year of Kyotoku) and lasted approximately 28 years until the urban-rural union (tōhi gattai) in 1483 (the fifteenth year of Bunmei). The conflict was triggered by the assassination of Uesugi Norisada, the Kanto Regional Commander, by Ashikaga Shigeuji, the Kamakura kubo (deputy shogun in Kanto). This led to prolonged warfare in the Kanto region, with factions divided between the Kamakura side and the shogunate supporters, eventually developing into an upheaval that later became known as the "starting point of the Warring States period."

Ashikaga Shigeuji subsequently left Kamakura, relocated his base to Koga in Shimosa, and came to be known as the "Koga kubo." In response, the shogunate side sent a new Horigoe kubo to the Kanto region, which solidified the confrontational structure of a split in the Kanto Ashikaga clan. This rivalry was not completely resolved even after the Kyotoku Rebellion ended, and continued to influence Kanto politics throughout the Warring States period.

In the Kanto region, where the Muromachi shogunate's control system had become dysfunctional, powerful daimyo and regional warriors were forced to establish independent military forces. This situation fundamentally transformed the structure of sword demand. There was no room to procure high-quality swords from renowned production areas in Kinai and western Japan such as Kyoto, Yamato, and Bizen. Instead, systems for locally procuring practical swords in large quantities began to be established throughout the region.

The Explosive Growth of Sword Demand in the Kanto Region

Before the Kyotoku Rebellion, most swords sought by the warrior class in the Kanto region flowed in from western Japan. Tachi and katana from the Bizen Osafune school, celebrated works in the Soshu tradition, and swords forged by rising sword makers in Kyoto were delivered to the eastern provinces through merchants and deputy officials. However, during 28 years of warfare, this long-distance procurement route became increasingly disrupted.

In its place, a regional procurement system that could be called "Kanto local sourcing" came to the fore. Warrior groups from provinces such as Izu, Sagami, Musashi, Kozuke, Shimotsuke, Hitachi, Kazusa, and Shimosa began placing large orders for mass-produced swords with local blacksmiths. Mass-produced swords were swords without signatures and of mass-production quality, but they were sufficient for practical battlefield use—practical swords prioritizing function over refinement. To meet this demand, small-scale blacksmiths rapidly proliferated throughout the Kanto region.

It is thought that during this period, sword demand showed differentiation by social status. While commanders and upper-class warriors continued to seek swords from established production centers as before, as the numbers of conscripted ashigaru (light infantry) and common soldiers increased, an increasingly large proportion of their swords were supplied by mass-produced blades. The Kyotoku Rebellion, which became a protracted conflict, was thus a conflict that normalized such bipolar demand in the Kanto region.

The Rise of Regional Sword Makers — Blacksmiths of Musashi, Kozuke, and Hitachi

Regions where records of sword-making activity increased in the Kanto region following the Kyotoku Rebellion include Musashi (present-day Tokyo and Saitama Prefectures), Kozuke (present-day Gunma Prefecture), and Hitachi (present-day Ibaraki Prefecture). In particular, blacksmiths from Musashi are sometimes mentioned in literature from the Edo period onward as "Bushu mono" (Musashi works) and are remembered as a group that supplied practical swords during the period of warfare.

In Kozuke, continuous sword demand arose from the retainers of the Uesugi clan, which was caught in the turmoil. There are also traces of local blacksmiths beginning to forge diverse bladed weapons such as spears and naginata in addition to swords. In Hitachi, there are records of warrior groups from figures such as Oda and Satake, during the period of daimyo formation, protecting sword makers, and some researchers view this as the beginning of Mito blacksmithing from the Edo period onward.

Most of these "regional sword makers" were not highly skilled technicians producing famous swords, but rather agricultural or tool blacksmiths continuing from the Kamakura period who had converted their work to meet wartime demand. However, some sword makers acquired patrons among local warriors, refined their techniques, and eventually developed into official sword makers for later Warring States daimyo. Protection in the form of local lords housing blacksmiths near their estates and providing them with stipends to make them exclusive artisans appears to have been seen in various places, and some scholars view this as the prototype for later "retainer blacksmiths" (okamae kaji).

It is also characteristic that many of these regional sword makers were unsigned or had no recorded lineage. The emphasis on estimating attribution by "which province and period the work comes from" rather than individual maker names is a common feature of Kanto swords from the Kyotoku Rebellion period.

The Economics of Mass-Produced Swords — The Logic of Quantity Over Quality During Wartime

On the battlefields of the Kyotoku Rebellion, the significance of individual warriors possessing famous swords diminished, and demand for practical, easy-to-use, readily available swords increased. This was the direct factor that drove the expansion of the mass-produced sword market.

The manufacturing cost of mass-produced swords was far lower than individually commissioned forgings. By forging multiple blades in succession with the same specifications, consumption of charcoal, the number of hammer-work steps, and the number of quenching cycles could be streamlined. While consistency in quality was low, for soldiers actually using them in battle, the criterion of "not breaking, not bending, and cutting well" took priority.

It is generally noted that mass-produced swords tended to favor quick-to-finish straight-edge (suguha) quenching and simplified nakago finishing over careful cosmetic polishing or complex hamon patterns. This was not aimed at artistic perfection but can be understood as a rational choice to balance battlefield durability with production efficiency.

This demand structure represented a major business opportunity for regional blacksmiths in the Kanto region and was simultaneously a place for accumulating mass-production techniques. The techniques developed by sword-making groups that took root in various parts of the Kanto region during this period became the foundation for the systematic military procurement systems of Warring States daimyo from the 16th century onward and eventually came to be positioned as the prehistory of Edo sword-making culture during the Tokugawa period.

What the Kyotoku Rebellion Left in Sword History

The Kyotoku Rebellion brought about particularly notable turning points in the history of the Japanese sword in two respects.

First, the geographical diversification of sword production. The production of high-quality swords, which had previously been concentrated in limited centers such as Kyoto, Yamato, and Bizen, became an opportunity for sword makers to establish themselves throughout the eastern provinces due to increased Kanto demand. This became the foundation for diverse regional sword-making cultures in the subsequent Warring States period.

Second, the acceleration of swords becoming "tools." Until the early Muromachi period, warrior swords retained strong aspects as symbols of formal attire and authority, but after the Kyotoku Rebellion, there were increasing instances where swords came to be recognized as more purely practical combat tools. This shift became the intellectual foundation leading to the "practical sword era" of the Azuchi-Momoyama and early Edo periods.

The 28 years of the Kyotoku Rebellion changed the Kanto warriors' view of swords, planted the seeds of regional sword-making culture, and served as an important historical catalyst in shaping the later history of the Japanese sword.

What You Should Know When Appraising and Collecting Swords from the Kyotoku Rebellion Period

If you currently have the opportunity to handle a sword believed to have been made in the Kanto region during the Kyotoku Rebellion period, the first point to understand is that "being unsigned is not uncommon." Mass-produced swords, by nature, had little concept of individual makers naming themselves, and many regional blacksmith works had no signatures cut at all. Therefore, the focus of appraisal becomes comprehensive positioning based on characteristics of period, province, and form (sugata) rather than identifying specific sword makers.

When confirming the positioning of such unsigned swords, authentication certificates issued by appraisal organizations such as NBTHK (the Society for Preservation of Japanese Art Swords) become important resources. Even for swords where the maker cannot be identified, such certificates serve the role of providing objective verification to provincial works with limited provenance by demonstrating the consistency of period, province, and form from a professional perspective.

In the practical aspects of collecting and purchasing, confirming the following points can help with decision-making.

• Whether the time period and province stated in the authentication certificate are not contradicted by the overall time-period perspective suggested by the nakago finish, file marks (yasurieme), and overall form, not just the presence or absence of a signature
• How elements indicating a history as a battlefield sword, such as wear from sharpening and repairs to blade chips, are recorded and explained
• When provenance (the previous owners it has passed through) is known, how far that information substantiates the sword's background

Kanto swords from the Kyotoku Rebellion period, including mass-produced blades, operate under a different evaluation framework than ornate art swords. That is, value is found not so much in refined jihada or beautiful hamon patterns, but in the historical authenticity of the sword itself as a practical tool that survived the era of warfare. Surviving examples are never numerous, and a single blade whose historical context is substantiated by an authentication certificate transcends mere military equipment to hold meaning as a resource that narrates the very transitional period as the Kanto region entered the Warring States era.