The Kan'nō Disturbance

The Kan'nō Disturbance: The Greatest Internal Conflict of the Muromachi Shogunate Born from Bitter Fraternal Strife of the Ashikaga Brothers

From Kan'nō 1 (1350) to Kan'nō 3 (1352), the "Kan'nō Disturbance (Kan'nō no jōran)," which shook the newly founded Muromachi shogunate to its very foundations, stands as one of the most complex internal conflicts in Japanese medieval history. The principal figures in this struggle were two brothers: Ashikaga Takauji (1305–1358), founder of the Muromachi shogunate, and his actual younger brother Ashikaga Tadayoshi (1306–1352). The elder brother excelled in martial prowess and, as Seii Taishogun, embodied the military authority of the shogunate; the younger brother, gifted in administrative affairs, oversaw the shogunate's governance and judiciary. Why did two figures who should have been complementary descend into bitter fraternal strife? Behind this lay both the turbulent age of the Northern and Southern Courts period and profound contradictions within the shogunate's power structure.

The Collapse of the Kenmu Restoration and the Founding of the Muromachi Shogunate: Birth of the Dual Leadership System

After the Kenmu Restoration (1333–1336) of Emperor Go-Daigo collapsed, Ashikaga Takauji established the Muromachi shogunate in 1336. In the age of the Northern and Southern Courts, when the Southern Court (forces of Emperor Go-Daigo) and the Northern Court (forces of Emperor Kōmyō) coexisted, Takauji sought to establish the shogunate's legitimacy by supporting the Northern Court. During this period, the shogunate's actual authority was administered through a dual leadership system between Takauji and Tadayoshi: Takauji wielded military power and authority as Seii Taishogun, while Tadayoshi oversaw the shogunate's administration and judiciary—a complementary division of labor.

However, the stability of this system was disrupted by the figure of Kō no Moronao (?–1351), who rose to power as Takauji's administrator (shikken) and wielded enormous authority. Moronao possessed exceptional administrative skill and enjoyed Takauji's absolute trust, yet he stood in fierce opposition to Tadayoshi on both policy and power-base grounds. Moronao's clan pursued practical interests in territorial control, fundamentally incompatible with the courtly and legalistic order that Tadayoshi sought to maintain.

Swords as Witnesses to the Northern and Southern Courts Battlefields: The Era of the Great Sword

The Northern and Southern Courts period (1336–1392), when the Kan'nō Disturbance erupted, marked a crucial turning point in Japanese sword history. During this era, large blade weapons called "ōdachi" (great swords) or "nodachi" (field swords)—which had developed in the late Kamakura period—were extensively deployed on the battlefield. As the Northern and Southern Courts conflict prolonged across the nation, warriors pursued sword utility in actual combat with single-minded intensity, resulting in dramatic transformations in blade design.

The tachi of the Northern and Southern Courts period differed markedly from Kamakura-era swords' graceful curves, having evolved toward more practical forms. Swords exceeding 90 centimeters in blade length appeared, designed to be wielded with both hands while walking, delivering strikes downward against mounted enemies. This change reflected the realities of the battlefield created by the Northern and Southern Courts conflict—protracted siege warfare and infantry-centered group combat—marking the transition from the age of single mounted-warrior duels to an era where foot soldiers fought in organized formations. This fundamental shift in combat tactics reshaped how swords themselves were deployed.

The generals who participated in the Kan'nō Disturbance likewise wielded tachi of this era. In particular, large swords forged by Kanemitsu, the renowned blade smith of the Bizen Osafune school who exemplified the age, were prized by the period's warriors. Known as "Osafune Kanemitsu," these blades are remembered as masterpieces marrying practical utility with aesthetic refinement, with many examples surviving to the present. Similarly, swords from the Sōshū tradition (Sagami Province: modern Kanagawa Prefecture)—from the lineages of blade smiths such as Yukimitsu and Sadamune—were actively employed by the era's generals. With their rough nie (granular hardening patterns) and dynamic hamon (blade patterns), Sōshū-tradition swords embodied the turbulent spirit of the Northern and Southern Courts age with striking intensity.

Kō no Moronao and Ashikaga Tadayoshi: The Collision of Two Political Ideologies and the Outbreak of Conflict

The opposition between Kō no Moronao and Ashikaga Tadayoshi transcended mere power struggle, representing a fundamental philosophical divide. Moronao was a pragmatist and realist who prioritized substantive rule through military force over the authority of the emperor or court aristocracy. Tadayoshi, by contrast, despite leading a military regime, valued courtly order and etiquette, seeking to maintain a system wherein the shogunate respected imperial authority. "Only military force rules the world" versus "a military regime gains legitimacy through propriety and law"—this fundamental tension illuminates an essential paradox in Japanese warrior culture. Should those who carry swords preserve social order through propriety, or should sword power itself become the source of order? This is a fundamental question of bushidō.

Moronao sharply criticized Tadayoshi and moved to strip him of political authority. In Kan'nō 1 (1350), Tadayoshi protested Moronao's overreach by announcing his withdrawal to monastic life, destabilizing the shogunate's power structure. Moronao pressed to eliminate Tadayoshi, bringing armed conflict to the brink. Regional daimyo and military lords throughout the realm faced demands to align with either the Takauji-Moronao faction or the Tadayoshi faction, precipitating nationwide upheaval.

The Southern Court Defection Strategy and Moronao's Execution: A Dramatic Reversal

Tadayoshi broke the deadlock through a bold gambit: defection to the Southern Court. Submitting to the Southern Court (Emperor Go-Murakami's forces), Tadayoshi leveraged Southern Court authority to draw powerful Northern Court generals to his side. As the Northern-Southern divide interwove complexly with the shogunate's internal power struggle, the embattled Takauji-Moronao faction had no choice but to capitulate. In Kan'nō 2 (1351), the brothers Kō no Moronao and Kō no Moroyasu were executed by Uesugi Yoshinori, acting for the Tadayoshi faction, while being escorted near the Muko River in Settsu Province.

After Moronao's death, Takauji and Tadayoshi achieved temporary reconciliation, though their relationship never fully healed. Tadayoshi withdrew to Kamakura, gathering support from regional samurai and resuming an oppositional stance toward the shogunate. Takauji pursued Tadayoshi down the Tōkaidō, defeating Tadayoshi's forces at the Battle of Satta Pass in Suruga Province (modern Shizuoka). In the second month of 1352, Tadayoshi died at Jōmyō-ji temple in Kamakura—reportedly by poisoning. The brothers' quarrel concluded with the younger brother's death.

What the Kan'nō Disturbance Left Behind in Japanese History: The Transformation of Warrior Culture and Sword-Making

Perhaps the most significant impact of the Kan'nō Disturbance on Japanese sword history was the explosive growth in sword demand during the turbulent Northern and Southern Courts era and the resulting "democratization" of sword culture. As nationwide internal conflict prolonged, demand for swords as weapons surged dramatically. Blade smiths from all regions—Bizen Osafune, Yamato, Sōshū, Mino—forged quantities of blades, and not merely upper-ranking warriors but regional gentry and even peasants became armed. Swords from this era possessed dual character: both pure works of art and mass-produced practical weapons.

Moreover, the Kan'nō Disturbance tested a fundamental proposition of bushidō: loyalty to one's lord. Each general faced the judgment of which faction—Moronao's or Tadayoshi's—represented legitimacy, forced to risk their lives on that choice. Some changed allegiance mid-conflict, and the raw conflict between samurai honor and survival instinct is starkly recorded. "Choosing one's lord" carried weight equivalent to the weight of the sword one bore—it embodied the essential question of living as a samurai.

Even after the Kan'nō Disturbance, Takauji remained in office as shogun, yet the shogunate's authority had suffered greatly. The Northern and Southern Courts conflict persisted until 1392 (Ōei 3) with the unification, and sword culture during this interval shifted decisively toward mass production and practical utility. The shogunate's weakening that would lead to the Ōnin War (1467) can trace its origins in part to the Kan'nō Disturbance. The "lost alternative history" of the Muromachi shogunate—what form it might have taken had Tadayoshi survived—testifies to the profound impact of the Kan'nō Disturbance on the course of medieval Japan.

Sasaki Dōyō and the Basara Daimyo: The Warrior Culture Liberation Born from the Kan'nō Disturbance

Among the distinctive cultural phenomena born from the turbulent Kan'nō Disturbance era arose what came to be known as "basara," a unique aesthetic sensibility among warriors. Basara meant rejecting traditional propriety and formality, instead displaying oneself through lavish and unconventional dress and conduct—a Muromachi early-period warrior culture exemplified by Sasaki Dōyō (1296–1373).

Dōyō skillfully maneuvered between the Moronao and Tadayoshi factions during the Kan'nō Disturbance and ultimately survived. The swords he possessed were adorned with elaborate koshirae (sword fittings), treating the blade not merely as a weapon but as an ornamental object through which to display personal aesthetic sensibility and authority. Richly decorated scabbards and hilts inlaid with gold and silver, tsuba (guards) scattered with precious stones—this "basara sword culture" became the prototype for the lavish sword-mounting culture of later Muromachi and Sengoku-period commanders.

Paradoxically, the power vacuum created by the Kan'nō Disturbance brought liberation to warrior culture. In an age of confusion over legitimacy, warriors asserted their identity through their swords, armor, and personal adornment. The "culture of adorning swords" nurtured during this period connected to the "Higashiyama collection" (Higashiyama gomitsu)—art objects gathered by Ashikaga Yoshimasa—leaving an important legacy in Japanese art history.