Isshi Incident — Prelude to the Taika Reforms

On the 12th day of the 6th month of Kōgyoku 4 (July 10, 645 CE), at the Asuka court (present-day Asuka Village, Nara Prefecture), Soga no Iruka was stabbed to death by Prince Naka no Ōe (later Emperor Tenji) and Nakatomi no Kamatari (later Fujiwara no Kamatari) and their faction. Known as the Isshi Incident (Isshi no Hen), this coup brought to an end the dominance of the Soga clan, which had held power for approximately 150 years, and marked the starting point for the transition to a ritsuryo state centered on the emperor — the transformation known as the Taika Reforms. As one of the first historically documented instances in which the straight swords (chokutō) of the ancient period — the precursors of the Japanese sword — were actually used in a political assassination, this event is also of special note in the history of Japanese swords.

The Soga clan was a powerful family that actively absorbed Buddhism, culture, and institutional models from the continent during the late sixth and early seventh centuries. Through four generations — Iname, Umako, Emishi, and Iruka — they wielded enormous power, forging marriage ties with the imperial family and effectively controlling national governance. Soga no Umako in particular co-administered government with Prince Shōtoku (Prince Umayado) from 593 onward; but after the death of Empress Suiko (628), the father-and-son pair of Emishi and Iruka increasingly tyrannized both the imperial family and other powerful clans. In 643, they drove Prince Yamashiro no Ōe to suicide, and with this act the tyranny of Soga no Iruka reached its apex.

Prince Naka no Ōe, son of Empress Kōgyoku, harbored an acute sense of crisis about the Soga clan's lawlessness. His collaborator was Nakatomi no Kamatari, a learned man of the Nakatomi clan who had forged a deep bond with Naka no Ōe through scholarship. Also involved as an inside agent was Soga no Kurayamada no Ishikawamaro. Though a member of the Soga clan, Ishikawamaro was alarmed by Iruka's overbearing dominance.

The setting for the assassination was a formal court ceremony in which envoys from the Three Kingdoms of Korea (Paekche, Silla, and Koguryō) were to be received. The rite was to be held in the Great Hall of State (Daigokuden) at Asuka, and Iruka, like all attendants in the presence of the empress, was required by protocol to leave his sword outside before entering. Naka no Ōe and his allies exploited this opportunity, choosing the moment when Iruka would be disarmed to execute their plan.

When the ceremony began, Soga no Kurayamada no Ishikawamaro took the role of reading aloud the written tributes from the Three Kingdoms, deliberately prolonging the recitation to buy time. Naka no Ōe ordered the gates closed to cut off any escape; then two executioners, Saeki no Muraji Komaro and Katsuragi no Wakainukai no Amita, drew their swords (straight-bladed chokutō) and attacked Iruka. The first blow wounded Iruka on the head and face; he fell before Empress Kōgyoku and cried out for her protection, but the empress withdrew to the inner chambers. Naka no Ōe is said to have personally taken up his sword to deliver the final blows. Iruka was killed on the spot.

The following day (the 13th day of the 6th month), Soga no Emishi set fire to his own residence and took his own life in the flames, burning down the historical chronicles he had been compiling along with the building. With this, the main Soga lineage was extinguished. Among the chronicles burned by Emishi are believed to have been the Kokki (National Records) and Tennōki (Imperial Records), and it is said that a portion of ancient Japanese history was permanently lost.

In the year following the Isshi Incident (646), the "Edict of Reform" (Kaishin no Mikotonori) was promulgated. This edict formed the core of the Taika Reforms, initiating the construction of a centralized state modeled on Chinese ritsuryo institutions: public ownership of land and people (kōchi kōmin), the establishment of a provincial and district administrative system, land allocation under the handen shūju system, and the reorganization of taxation.

Why is the Isshi Incident significant from the perspective of Japanese swords and the history of bladed weapons? First, it demonstrates that the "sword" (tachi/katana) in ancient Japan was not merely a ritual implement or a symbol of status, but also a practical weapon actually used in political assassination. The dominant sword type of the Asuka period was the chokutō — the straight-bladed sword (single- or double-edged) influenced by continental models from China and Korea — which became the prototype for the curved Japanese sword (tachi and uchigatana) of later centuries. This incident is recorded as the moment when the ancient forerunner of the Japanese sword actually moved history.

Second, the fact that the assassination took place at a court ceremony is itself significant. One can read from this event that a social and spatial order already existed governing who was permitted to carry swords (warriors and nobles) and where (not in the imperial presence). The very premise of the plan — that Iruka would remove his sword before entering — vividly illustrates the dynamics of etiquette, power, and the sword.

Third, the ritsuryo state system established after the Taika Reforms formed the social foundation from which the buke (warrior class) later emerged. The organization of military and policing functions under the ritsuryo system led to the birth of the "samurai" in the Heian period, making this moment one of the historical starting points for the formation of the inseparable relationship between the warrior and the sword.

The Isshi Incident holds a permanently important place in the cultural history of the Japanese sword and in Japanese political history as the moment when a small number of people bearing swords fundamentally changed the structure of power at the very center of the court.