The Onin War and the Sword Industry: How the War Transformed Bizen and Mino Forging Systems and Sword Distribution

The "Ōnin War" (1467–1477) left deep and wide scars across Japanese politics, society, and culture. Its impact extended to the Japanese sword industry as well, fundamentally transforming the structure of pre-existing sword production and distribution. This article analyzes the Ōnin War as a "turning point in sword industry history," examining the contrasting fortunes of the two major production centers—Bizen (present-day Okayama Prefecture) and Mino (present-day Gifu Prefecture)—and the advent of the era of mass production of kazuuchimono (量打ち物).

The Sword Industry Before the Ōnin War—The Monopoly of Bizen Osafune

Before the Ōnin War, the Japanese sword industry was in what could be called "a situation of near-monopoly by Bizen Osafune." While sword smiths certainly existed in Yamashiro, Yamato, Sōshū, and Mino, Bizen Osafune held an overwhelming position in terms of production volume, quality, and distribution networks.

Bizen Osafune's prosperity had multiple causes. First, it lay close to areas rich in high-quality iron sand (the Chūgoku Mountains) and had abundant wood charcoal resources needed for smelting. Second, an advanced distribution network utilizing water transport on the Osafune River and Yoshii River enabled the distribution of finished swords nationwide via the Seto Inland Sea. Furthermore, a brand identity as a "renowned sword-producing region" established since the Ashikaga shogunate and Emperor Gotoba ensured stable demand from the court nobility, warrior class, and temples and shrines.

In the 1460s, immediately before the Ōnin War, Bizen Osafune housed multiple workshops representing lineages of renowned smiths from the Kamakura through Muromachi periods—such as Kagemitsu, Kanemitsu, Nagayoshi, and Motoshige—with estimated annual production exceeding half of nationwide demand including the eastern provinces.

The Impact of the Ōnin War—A Direct Blow to Bizen Osafune

When the Ōnin War erupted, Bizen Osafune received a double blow. The first was "the severing of distribution networks." War disrupted land and maritime traffic on the Sanyōdō route and the Seto Inland Sea, making shipment to Kyoto and the Kinai region—Bizen swords' main market—difficult.

The second was "a sudden shift in demand." In peacetime, sword demand centered on individual custom orders: "commissioning a single high-quality sword over several years." However, as warfare escalated, regional daimyo and local lords sought "practical combat swords available in large quantities immediately." The intricate Bizen sword-making process—the complex hamon formation through earth-setting quenching—was poorly suited to meeting this new demand.

Furthermore, conflict reached Bizen itself, and the Osafune workshops suffered direct damage. Historical records from the war period document that Osafune smiths were temporarily scattered. In this chaos, some sword craftsmen left Bizen and relocated to serve powerful regional lords elsewhere. This "dispersal of sword smiths" became an opportunity for techniques previously concentrated in Bizen to spread throughout the country.

The Rise of Mino Swords—Responding to Real-Combat Demand

With the Ōnin War as the turning point, the sword industry of Mino (present-day Gifu Prefecture) rose rapidly. The center of Mino was Seki, where a collective of sword smiths called the "Seki smiths" (sekikaji) concentrated.

Mino swords succeeded in meeting wartime demand through "rational production processes." Rather than Bizen's intricate chōji hamon, Mino smiths excelled at practical hamon patterns—"gume" and "suguha"—formed through processes that achieved stable quality in relatively short timeframes and suited mass production.

Additionally, Mino occupied "a strategic point in overland trade routes." Mino Province lay at the intersection of the Tōkaidō, Nakasendō, and Hokuriku roads, making the sword industry centered in Seki advantageous for distribution to both eastern and western regions. As wartime trade increasingly emphasized overland routes, Mino enjoyed an advantage over Bizen's water-transport-dependent position.

From after the Ōnin War through the Warring States period, the number of sword smiths in Mino Seki increased rapidly. Lineages such as Kanemoto and Kanesada established fame as "wazamono"—swords with exceptional cutting ability—and received commissions from warring daimyo nationwide. The Mino sword "mago-roku Kanemoto" became one of the most widely used uchigatana of the Warring States period, appearing repeatedly in military treatises and chronicles.

The Establishment of the Kazuuchimono Economy—The Separation of Mass Production and Quality

The decisive change that appeared in the sword market after the Ōnin War was the proliferation of "kazuuchimono." Kazuuchimono refers not to individual commissioned orders but to swords produced in large quantities through standardized and regularized processes.

Mino was the center of kazuuchimono production, though Bizen also produced them. Quality was inferior to individually commissioned work, but prices were substantially cheaper and large-scale procurement was possible. When Warring States daimyo equipped thousands to tens of thousands of soldiers, providing all of them with commissioned swords from renowned smiths was impossible. Kazuuchimono filled this need.

The establishment of the kazuuchimono economy created a "bifurcation" of the sword industry. The upper tier consisted of "individually commissioned work by master smiths"—high-priced, high-quality items for daimyo and senior-ranked warriors. The lower tier comprised "mass-production sword smiths and forges producing kazuuchimono"—low-priced, standard-quality items for common soldiers and minor samurai families. This two-tiered structure continued into the Edo period and beyond, becoming a distant prototype of the modern market structure: "Living National Treasure swords versus mass-produced iaido swords."

The Dispersal of Kyoto Sword Smiths—Acceleration of Technology Propagation

The Ōnin War brought devastating damage to Kyoto, and sword smiths of Yamashiro (Kyoto) suffered major setbacks. Some Kyoto sword smiths from lineages such as Sanjō, Awata-guchi, and Rai sought safer lands during the chaos and relocated to various regions.

This "dispersal of Kyoto sword smiths" resulted in spreading techniques previously concentrated in Kyoto throughout the nation. For example, Rai lineage techniques can be confirmed in genealogical records as later influencing sword smiths in remote regions such as Satsuma and Kii. The geographic dispersal of techniques meant industry collapse in the short term, but contributed to the overall advancement of Japanese sword techniques nationwide in the long term.

Conclusion—The New Order of the Sword Industry Created by the Ōnin War

The Ōnin War brought the following structural changes to the Japanese sword industry: Bizen Osafune's distribution monopoly collapsed, and new production centers centered on Mino and Seki rose to prominence. A mass-production system for kazuuchimono was established, and the sword market transformed from "a market for quality" into "a dual market for both quantity and quality." The geographic dispersal of sword smiths advanced, accelerating the nationalization of sword-making technology.

To understand Warring States period swords—ranging from anonymous kazuuchimono used by common soldiers to individually commissioned work by master smiths favored by influential generals—understanding this industrial structure created by the Ōnin War is essential.