Assassination of Minamoto no Sanetomo — End of the Minamoto Shogunal Line

On February 13, 1219 (Kenpō 7/1/27), Minamoto no Sanetomo, the third shōgun of the Kamakura shogunate, finished the ceremony of thanks (haiga) for his appointment as Minister of the Right (Udaijin) at Tsurugaoka Hachimangū. While he was descending the long stone staircase, his nephew Kugyō shouted, "Thus shall I strike down my father's enemy!" and cut off his head with a long sword. Sanetomo was 28. The incident ended the direct line of Minamoto shōguns that had begun with Minamoto no Yoritomo, after only three generations, and it marked a decisive turning point in the history of warrior government.

Minamoto no Sanetomo's Life and Appointment as Minister of the Right

Minamoto no Sanetomo was born in Kenkyū 3 (1192), the second son of Minamoto no Yoritomo and Hōjō Masako. In Ken'nin 3 (1203), his elder brother Yoriie was driven from the shogunate by the Hōjō and others, and Sanetomo became the third shōgun at only twelve years old. (Yoriie was assassinated the following year, Genkyū 1 (1204).) Watching Yoriie's political failures and the rise of the Hōjō, Sanetomo largely entrusted actual authority as shogun to the shikken, including Hōjō Yoshitoki and Hōjō Tokimasa.

Sanetomo himself had the temperament of a man of culture rather than a warrior, and he was accomplished at waka poetry. The Kinkai Wakashū preserves his outstanding poetic talent to this day. In politics, he valued cooperation with the imperial court and kept good relations with Retired Emperor Go-Toba. In Kenpō 6 (1218), he became the first warrior to be appointed Minister of the Right. The following year, he visited Tsurugaoka Hachimangū for the ceremony of thanks for that appointment, and that visit became the site of his death.

Kugyō's Motive and the Course of the Assassination

Kugyō was the second son of the second shōgun, Minamoto no Yoriie, and Sanetomo's nephew. When his father Yoriie was confined and assassinated at Shuzenji in Izu, Kugyō was only five years old. He later became Sanetomo's adopted son and was appointed chief administrator (bettō) of Tsurugaoka Hachimangū. He is said to have become convinced that his father's enemy was his uncle Sanetomo. On the night of the 27th day of the 1st month of Kenpō 7, with snow on the ground, Kugyō lay in wait for Sanetomo as he left after the ceremony of thanks. He is said to have been hiding in the shadow of the great ginkgo tree beside the stone steps, and he struck off Sanetomo's head with a long sword. When the retainers rushed to the scene, only Sanetomo's headless body was lying on the stone steps.

Kugyō's band also cut down Minamoto no Nakaakira, who had been in attendance. Kugyō then tried to flee to the residence of Miura Yoshimura, but he was cut down by Yoshimura's retainers. Kugyō was 20. As for the mastermind who manipulated Kugyō from behind, there are several theories, including theories that name Hōjō Yoshitoki, Miura Yoshimura, and Retired Emperor Go-Toba. It remains a historical mystery to this day.

Political Consequences: Establishment of Regency Government and the Foreshadowing of the Jōkyū War

The assassination of Minamoto no Sanetomo completely severed the line of Minamoto shōguns that had continued since Minamoto no Yoritomo. The shogunate welcomed Fujiwara no Yoritsune, a court noble from Kyoto, as its new shōgun (the fourth shōgun). It then shifted to a system in which nominal shōguns without Minamoto blood followed one another: regent-house shōguns (sekke shōgun) and imperial-prince shōguns (shinnō shōgun). Actual power remained in the hands of the Hōjō as shikken, and regency government (shikken seiji) took root in effect as the form of warrior government.

Two years after Sanetomo's assassination, in Jōkyū 3 (1221), Retired Emperor Go-Toba issued a decree of the retired emperor (inzen) to pursue Hōjō Yoshitoki, and the Jōkyū War broke out. This was the result of the collapse of the cooperative court–shogunate arrangement that had been maintained during Sanetomo's lifetime, and of the tensions between the court and the shogunate coming to the surface. When the shogunate's forces won the Jōkyū War, the shogunate established the Rokuhara Tandai to strengthen its supervision of the court. Warrior rule was then progressively established nationwide.

Relationship to Sword Culture: Warrior Ceremonial Etiquette and the Political Meaning of the Tachi

The tachi used at the ceremony of thanks for Minamoto no Sanetomo's appointment as Minister of the Right was part of the costume indispensable to warrior ceremonial dress. From the late Heian period through the Kamakura period, the etiquette of wearing the sword (haitō) was established. When warriors attended court ceremonies, they suspended a tachi from the waist.

The Kamakura period was also an age in which the style of the Japanese sword developed greatly. The period around the Jōkyū War (1221) was a golden age in which sword-smith groups centered on Yamashiro, Yamato, and Bizen produced one masterpiece of kotō ("old swords") style after another. Smiths of the Awataguchi school and the Ichimonji school of Bizen were active and met the practical demand of Kamakura warriors. After the Hōjō established their control following Sanetomo's assassination, demand for smiths serving the shogunate rose. This led to a further flourishing of sword culture centered on Kamakura.

Bizen and Yamashiro kotō made in the age in which Sanetomo lived are still preserved today as National Treasures and Important Cultural Properties in museums across the country. The historical rupture of Minamoto no Sanetomo's assassination both signaled the end of one era of Kamakura warrior culture and marked the dawn of a new age, in which sword craftsmanship would further develop under the stable regency system of the Hōjō.