Independence of Northern Kanto Swordsmiths After the Kyotoku War

The Shōtoku Disturbance and the Foundation of Northern Kantō Swordsmithing

The Shōtoku Disturbance (1455–1483) was a 28-year civil conflict in Kantō during which sword craftsmen in northern Kantō broke free from existing power structures and transformed into independent production centers. The disturbance began with an incident in Shōtoku 3 (1454), when the Kamakura Kubō Ashikaga Shigeuji assassinated Uesugi Noritada, the Kantō Kanrei. From the following year, the Yamanouchi and Ōgigayatsu Uesugi clans and Bakufu forces battled Shigeuji, expanding conflict across the entire Kantō region.

Shigeuji subsequently relocated his base to Koga (present-day Koga City, Ibaraki Prefecture), adopting the title "Koga Kubō," and engaged in prolonged conflict with the Muromachi Bakufu, which supported the Kantō Kanrei Uesugi clan. Sporadic fighting continued for 28 years until the "Tōhi Wakoku" (capital-countryside reconciliation) was established in Bunmei 14 (late 1482 to early 1483), and this disturbance is positioned as the effective beginning of the Sengoku period in the Kantō region.

The Geopolitics of Sword Production in Kantō

The Five Schools (Yamato, Yamashiro, Bizen, Sōshū, and Mino) were the primary centers of high-quality sword production in the early Muromachi period, and Kantō samurai depended on these regions for sword procurement. However, when the Shōtoku Disturbance erupted, the flow of goods from the capital was disrupted, making it an urgent necessity to establish a system for stable local weapons procurement.

In particular, the following regions served as border zones between Koga Kubō forces and the Yamanouchi and Ōgigayatsu Uesugi forces, making them sites of intense conflict, and local procurement became especially critical.

• Shimotsuke (present-day Tochigi Prefecture)
• Hitachi (present-day Ibaraki Prefecture)
• Kōzuke (present-day Gunma Prefecture)

The Sōshū School (present-day Kanagawa Prefecture) was an excellent center that had produced master craftsmen such as Masamune and Sadamune during the Northern and Southern Courts period, but the Kantō conflicts disrupted the Sōshū smiths' supply network. This supply shortage became the direct catalyst for the rise of local smiths throughout northern Kantō.

The Economic Independence Mechanism of Local Smiths

As conflict persisted, demand for weapons in regions independent of Kyoto's and Sōshū's renowned smiths surged. It became customary for regional lords to commission sword production directly from local smiths. Craftsmen who had previously depended on the goban kaji (official smith) system began constructing independent economic spheres.

The goban kaji were groups of sword artisans assembled and housed in Kyoto by the Muromachi Bakufu, who supplied swords to the Bakufu and the shogunal household. During the period when this system functioned, regional sword craftsmen experienced only supplementary roles, but as the Bakufu's effective control over Kantō was lost due to the Shōtoku Disturbance, regional production centers filled this vacuum. In Kantō, regional lords established relationships with sword craftsmen, providing them with fixed stipends as retained retainers and receiving priority supply of swords during wartime.

The Proliferation of Kazuuchi Swords and the Shift to "Quantity over Quality"

During this period, mass-produced "kazuuchi" swords rapidly spread throughout northern Kantō. Kazuuchi swords were standardized blades mass-produced without individual commissions, and by drastically reducing production costs per blade, they provided the economic foundation for arming ashigaru foot soldiers. The prolonged Shōtoku Disturbance expanded the scale and frequency of armed conflicts from battles between major daimyo to skirmishes at the village level, and demand for inexpensive swords grew proportionally.

Based on inference from later historical records, the prices of swords meeting this demand ranged from several hundred to several thousand mon (equivalent to tens of thousands to hundreds of thousands of yen in modern currency), and as inexpensive "practical goods" compared to famous blades from the capital, they circulated throughout northern Kantō.

The Limits of Muromachi Bakufu Control over Sword Craftsmen

As the Kyoto goban kaji system ceased to function, a "domestic production network" was formed in which regional lords directly employed smiths. This phenomenon occurred concurrently with the rise of smith communities in Mino (present-day Gifu Prefecture) during the same period. In Kantō as well, distinct demand centers emerged in the sphere of influence of the Koga Kubō (Shimosa and Hitachi regions) and the sphere of influence of the Yamanouchi and Ōgigayatsu Uesugi (Kōzuke and Musashi regions), leading to diversification of sword production centers.

Impact on Later Kantō Swordsmith Lineages

From the 16th to 17th centuries, this regional foundation led to the formation of sword-making schools unique to Kantō. The transition from "dependence on the center to regional independence" created by the Shōtoku Disturbance was an important turning point that became the starting point for geographic diversification of early modern sword craftsmen. As a classic example of warfare transforming industrial structure over 28 years, it constitutes a notably significant period in the history of Japanese swords. Furthermore, the establishment of mass production systems in Kantō during this period had great significance in laying the foundation in eastern regions for the proliferation of kazuuchi swords in the subsequent Sengoku period.

Warfare and the Transformation of Sword Distribution

Behind the prolonged Shōtoku Disturbance lay the decline of the Muromachi Bakufu's mediation capabilities and internal division within the Kantō Kanrei house (conflict between the Yamanouchi and Ōgigayatsu Uesugi clans). This structural power vacuum created constant demand for weapons, generating a stable income source for sword craftsmen. During the period of conflict, certain quantities of "battlefield salvage" from fallen warriors' swords re-entered circulation, but damage to blades and deterioration of the yakiba created demand for regrinding and repair. Such repair demand also contributed to the advancement of techniques and business stability among local smiths.

The tradition of local smiths that took root throughout eastern Japan through the Muromachi period also became a remote cause of sword-making schools that flourished in various regions during the Edo period's Shintō era. That the Shōtoku Disturbance, as the "beginning of the Sengoku period in Kantō," was one factor that substantially rewrote the map of Japanese sword production centers is an important recognition from the perspective of sword history.