Isshi Incident — Prelude to the Taika Reforms

On July 10, 645 (Kōgyoku 4/6/12), at the Asuka palace (present-day Asuka Village, Nara Prefecture), Soga no Iruka was stabbed to death by Prince Naka no Ōe and Nakatomi no Kamatari and their faction. This coup is called the Isshi Incident (Isshi no Hen). It put an end to the arbitrary rule of the Soga clan, which had held power for about a century since Soga no Iname, and it marked the starting point of the transition to a ritsuryō state centered on the emperor, the so-called Taika Reforms. It is also a notable event in sword history, as one of the first historical cases in which an ancient sword (chokutō), the origin of the Japanese sword, was actually used in a political assassination.

The Soga clan was a powerful family that actively accepted Buddhism, culture, and institutions from the continent from the late 6th to the early 7th century. Over four generations, Soga no Iname, Umako, Emishi, and Iruka wielded power and held effective control of state affairs, while forming marital ties with the imperial house. In particular, Soga no Umako governed together with Prince Shōtoku (Prince Umayado) in 593, but after the death of Empress Suiko (628), Emishi and his son Iruka became extremely arbitrary and came to oppress members of the imperial family and powerful clans alike. In 643, Soga no Iruka drove Prince Yamashiro no Ōe to suicide, and his arbitrary rule reached its peak.

Prince Naka no Ōe (later Emperor Tenji) was a son of Empress Kōgyoku and was deeply alarmed by the Soga clan's arrogance. The one who cooperated with him was Nakatomi no Kamatari (later Fujiwara no Kamatari). Kamatari was an intellectual from the Nakatomi clan who became closely tied to Prince Naka no Ōe through scholarship. Soga no Kurayamada no Ishikawamaro also secretly joined the plot. Ishikawamaro was a member of the Soga clan who nonetheless felt alarmed by Iruka's power.

The setting for the assassination was a court ceremony at which Soga no Iruka was to receive envoys from the Three Han (Baekje, Silla, and Goguryeo). The ceremony was scheduled to take place at the Great Hall of State (Daigokuden; the palace's main hall) in Asuka, and Iruka, as minister, was also expected to attend. Iruka was suspicious by nature and never let go of his sword day or night, but Nakatomi no Kamatari instructed a court entertainer (wazaogi) to have him remove his sword. Prince Naka no Ōe and the others took advantage of this opportunity and carried out the plan by striking at the moment Iruka had set his sword aside.

When the ceremony began, Soga no Kurayamada no Ishikawamaro took on the role of reading the memorial (petition) from the Three Han. Prince Naka no Ōe closed the gates to cut off escape routes and gave swords (chokutō) to two men, Saeki no Muraji Komaro and Katsuragi no Wakainukai no Amita, making them the executioners. But the two were too frightened to step forward, and Ishikawamaro, drenched in sweat, trembled in his voice. Prince Naka no Ōe himself leapt out and, together with Komaro and the others, slashed at Iruka's head and shoulder, and Komaro then cut one of his legs. Iruka stumbled toward Empress Kōgyoku's seat and appealed to her, but the empress withdrew silently into the hall, and Iruka was slain on the spot by Komaro and Amita.

The next day, the 13th day of the 6th month of Kōgyoku 4 (645), his father Soga no Emishi set fire to his own residence, burned historical records and other documents he had kept, and killed himself. With this, the main Soga family was destroyed. Among the books Emishi burned were reportedly the Tennōki and the Kokki, and it is recorded that only the Kokki was pulled from the fire by Fune no Esaka and presented to Prince Naka no Ōe.

In 646, the year after the Isshi Incident, the Edict of Reform (Kaishin no Mikotonori) was promulgated. This was the core policy of the Taika Reforms, and it set out on the path toward building a centralized state modeled on the Chinese ritsuryō system, including the kōchi kōmin system (direct state control of land and people), the kokugunri system (organization of local administrative districts), the handen shūju system (allotment of rice fields), and the development of a tax system.

Why is the Isshi Incident important from the perspective of Japanese swords and sword history? First, this incident shows that the sword in ancient Japan was not merely a ceremonial object or a symbol of rank, but a practical weapon used in an actual political assassination. Swords of the Asuka period were mainly chokutō (straight swords with no curvature, single-edged or double-edged) influenced by the continent (China and Korea), and they are the prototype of the later curved Japanese swords (tachi and uchigatana). This incident is recorded as the moment when ancient swords, the prototype of the Japanese sword, actually moved history.

Second, it is also important that the assassination took place at a court ceremony. The fact that the plan depended on making Iruka, who never let go of his sword day or night, remove it at the ceremony clearly illustrates the power dynamics surrounding the sword.

Third, the ritsuryō state system established after the Taika Reforms became the social foundation from which the buke (the warrior class) later emerged. The development of military and policing functions under the ritsuryō system led to the emergence of the bushi in the later Heian period, and became one of the historical starting points for the inseparable relationship between the bushi and the sword.

The Isshi Incident is an event that will forever hold an important place in the cultural and political history of Japanese swords, as the moment when a small number of people armed with swords fundamentally changed the structure of power at the heart of the court.