To Kill a Shogun: The Sad Tale of Minamoto no Sanetomo

To Kill a Shogun: The Sad Tale of Minamoto no Sanetomo

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Shogun Minamoto no Sanetomo is faced down by a warrior wielding a sword amidst falling snow in an illustration.
In 1219, the shogun Minamoto no Sanetomo, samurai lord of all Japan, was slain on the steps of Tsurugaoka Shrine in Kamakura, killed by his own nephew in cold blood. Who was Sanetomo - and why was he assassinated?

Snow blanketed the steps of Tsurugaoka Hachimangū Shrine as Shogun Minamoto no Sanetomo made his descent. By his side walked a single guard. It was a happy day for the ostensible samurai lord of all Japan; the emperor in distant Kyoto had just nominated Sanetomo to the post of Udaijin, Minister of the Right, one of the greatest honors the Japanese nobility could confer to one of the warrior class. After years of anxiety, of feeling disempowered, the imperial court had recognized Sanetomo’s importance as the shogun of the warrior capital of Kamakura. Sanetomo’s visit to the shrine had been in celebration of this momentous occasion. But the celebration would soon turn to tragedy.

Suddenly, a figure darted out from the side of the steep stone stairway. Sanetomo would have recognized the man – for not only was he the head priest of Tsurugaoka Hachimangū Shrine, he was also the Shogun’s own blood nephew and adopted son. Dressed in his flowing priest’s robes, Kugyō, once called Minamoto no Zensai, raised a sword aloft. Sanetomo’s guard had no time to react; Kugyō screamed, “With this, I avenge my father!” The sword flashed downwards, and blood flowed out onto the white of the snowdrifts. Minamoto no Sanetomo collapsed onto the shrine stairway. The Shogun was dead.

Minamoto no Sanetomo’s murder not only brought an end to the line of one of Japan’s great conquerers; it also helped usher in a war between the samurai and the emperor that would cement warrior power in Japan for more than six centuries to come.

To Kill a Shogun: The Sad Tale of Minamoto no Sanetomo

In 1219, the shogun Minamoto no Sanetomo, samurai lord of all Japan, was slain on the steps of Tsurugaoka Shrine in Kamakura, killed by his own nephew in cold blood. Who was Sanetomo – and why was he assassinated?

Watch a video version of this article on our YouTube channel.

Birth of the Shogunate

Sanetomo’s assassination came on February 12th, 1219, a scant few decades into what is now known as the Kamakura period – the first era of samurai rule in Japan. Sanetomo was the third Shogun of the Kamakura dynasty, the military government created by his father, Minamoto no Yoritomo, through violent conquest. Yoritomo had been a powerful ruler, wresting authority away from the emperor and the eternal capital of Kyoto. Yet upon his death, his wife’s family, the Hojo, had usurped true power from the Minamoto clan. Sanetomo had ruled as shogun in name only, while his mother, Masako, held the reigns of state alongside her father Tokimasa and brother Yoshitoki . And now, after long decades fearing for his life, he was gone. The shogun had been assassinated – and with it the very shogunal Minamoto line.

“Shogun” was an ancient title, even then. The official title was Sei-i Taishōgun (征夷大将軍, “Commander-in-Chief of the Expeditionary Force Against the Barbarians”), a designation granted by the emperor since at least the 8th century. The emperor awarded the title to military leaders sent forth to battle the indigenous Emishi clans in Japan’s northeast. By Sanetomo’s time, however, the “barbarian” Emishi were no longer a major threat. Instead, his father, Yoritomo, had been named “Shogun” in 1292 by Emperor Go-Toba to signal his military ascendancy.

Yoritomo had bested his rivals, the warriors of the Taira Clan, in the five-year Genpei War. Then, he’d turned his ire upon his younger brother, the popular military genius Minamoto no Yoshitsune. Yoshitsune died by his own hand in 1289, while his loyal companion Benkei, the legendary warrior monk, held off Yoritomo’s soldiers amidst a hail of arrows. From the very first, the Minamoto established their supremacy via ruthless violence against their own clansmen.

Yoritomo ruled Japan as Shogun from his base in Kamakura, and his sons and heirs received the title in turn. This was the beginning of “shogun” as a hereditary postion, and of samurai rule in Japan. Meanwhile, the imperial family continued to claim de jure power in Kyoto; the samurai government in Kamakura gained its legitimacy from Kyoto, all while supplanting temporal authority for its warrior bureaucracy. [4]

Minamoto no Yoritomo in black flowing robes, seated on tatami.
Shogun Minamoto no Yoritomo, founder of the Kamakura Shogunate. Image from 1179.

Minamoto no Sanetomo: The Tragic Shogun

Minamoto no Sanetomo was born in 1292, the very year his father Yoritomo received the shogunal title. He was the second son of the first shogun; his older brother, Yoriie, was born 10 years earlier. He grew up during the 14 years when his father was the undisputed military ruler of Japan.

While Sanetomo’s father, Yoritomo, wielded immense power, so too did his mother, Hōjō Masako. Over the years, her authority became so great she was known as “the Nun Shogun.” She’d only been 3 years old when Yoritomo, just a boy, was exiled to her father’s domain in Izu, the result of a failed rebellion by Yoritomo’s father. Later married to this son of an executed rebel, Masako’s entire family rose from obscurity to immense power as her husband’s army crushed the once-ascendant Taira. [3]

Masako gave birth to Sanetomo at her father, Tokimasa’s, mansion, located in the Minamoto’s eastern capital of Kamakura. Several ceremonies marked the occasion. Sanetomo’s father, the shogun, assembled his closest vassals and presented the newborn to them. Yoritomo proclaimed, “I want you all to focus together on the task ahead; safeguard the future!” He then had each vassal embrace the infant representing that future.

But upon Yoritomo’s death in 1299, the future the shogun had envisioned was forstalled. While Sanetomo’s older brother, Yoriie, was proclaimed the 2nd shogun, his own mother and her family, the Hojo, quickly usurped power for themselves. The Hojo became regents (執権, shikken) for the successive Kamakura shoguns. The regents wielded effective power, reducing the office of the shogun to a mere figurehead. All the while, the shogunate government was slowly eclipsing the power of the emperor in Kyoto.

Hojo Tokimasa depicted in woodblock print wearing black robes with Hojo family seal on sleeves.
Hojo Tokimasa, first shikken of the Kamakura Shogunate.

The Culling of the Minamoto

Young Sanetomo was close with his mother’s family, the Hojo. Not so his older brother, the Shogun Yoshiie, who favored the Hiki clan, another supportive vassal family of the late Yoritomo. Yoshiie was married to a Hiki, and bristling under the control of his grandfather Hojo Tokimasa, sought to have the Hiki supplant the Hojo as shogunal regants. When his mother Masako caught wind of these plans, she brought them to her father; Tokimasa invited the head of the Hiki family to his mansion and murdered him in cold blood. He then sent out shogunal soldiers to burn the Hiki mansion and kill the rest of the family line. This included Yoshiie’s firstborn son and heir, Minamoto no Ichiman, killed at only six years old.

But Yoshiie had another son – Minamoto no Zensai. Targeted for assassination, his grandmother interceded, not wanting another grandchild murdered. So, rather than being killed, or allowed to become heir to the shogunate, the five-year-old Zensai was instead legally adopted by his teenage uncle Sanetomo, and sent to a monastery. There, he received a new Buddhist name: Kugyo (公暁). The child was quickly shipped off to distant Kyoto to be trained in the ways of the Buddhist priesthood, far away from the violence in Kamakura.

The Shogun, Yoriie, was not quite so lucky. Despite his rage at the destruction of his family, he was powerless. Masako also wanted to protect him, and helped arrange for his abdication. He took the tonsure, and retired to a monastery on the Izu Peninsula. A year later, in 1204, assassins sent by the Hojo broke into the temple and killed the former shogun.

With the death of his brother, Sanetomo was now the shogun of all Japan, at the young age of 12. And yet, he had seen the deadly limits placed on the position his father had wielded with such authority. He knew the blade hovered over his head, ready to drop if ever he dared stand up to the family of his grandfather.

The Shogun and the Emperor

Sanetomo, fearful for his life, strove to stay in his mother’s family’s good graces. His true sense of loyalty, however, belonged to another faction: the imperial court in Kyoto.

From a young age, Sanetomo felt connected to the prestige and refined culture of the nobility. His father, Yoritomo, may have created a revolutionary warrior government, but he did so within a technical framework that claimed his government worked for the emperor.

(And Sanetomo cared deeply about precedents set by his father – at the age of 13, only a year into his tenure as shogun, he had his father’s former retainers bring him dozens of documents authored by Yoritomo. He copied them all down diligently, hoping to learn how to govern as shogun from his father’s example. [1])

As Shogun, Sanetomo took this official role as protector of the emperor’s realm seriously. He continually honored the retired emperor, Go-Toba, and received a number of traditional imperial titles in return. He even sought the hand of the emperor’s cousin in marriage; Kamakura records say that Sanetomo went over the heads of his mother and grandfather by corresponding with the imperial court to request an imperial wife. In 1204, not long after his brother’s death, he got his wish. Bomon Nobuko, first cousin of the emperor, left Kyoto, making the long journey to Kamakura. Their marriage was a happy one, although Nobuko never bore Sanetomo an heir.

Unsettled Times

Violence, plots, and paranoia continued to be ever-present during the first years of Sanetomo’s reign. In 1205, his grandfather and regent, Hojo Tokimasa, arranged for the murder of one of his own son-in-laws living in Kyoto. Sanetomo’s mother, Masako, fresh from facing the assassination of her firstborn Yoriie, suspected that Sanetomo was next on her father’s kill list. Word soon came to Masako and her brother Yoshitoki that their father and his second wife, Maki no Kata, intended just that; they meant to kill Sanetomo, and replace him with a shogun from the direct Hojo line.

Masako and Yoshitoki spirited Sanetomo away before the assassin’s knives could find him. Shortly after, they convened a council of state and used their influence to force their murderous father into retirement. Defeated, Tokimasa stepped down as regent, shaving his head and entering monastic exile in his home province of Izu. Yoshitoki succeeded him, becoming Kamakura shikken and protector of the young shogun Sanetomo.

Some months later, Sanetomo received a soon-to-be-published collection of waka poems from the retired emperor himself. Go-Toba knew Sanetomo appreciated poetry, and believed he would appreciate seeing his own father, Yoritomo’s, verse featured in the collection. This gesture likely drew the young shogun even closer to the court.

The Poet Shogun

According to scholar Kobayashi Naoki, Sanetomo “had a deep understanding of the ancient traditions of the aristocracy, in particular waka poetry, and he had great affection for them. He himself composed many waka and was famous as a poet.”

One of Sanetomo’s poems was even included in the Hyakunin Isshu, a famous contemporary collection of 100 poems by 100 prestigious poets:

世の中は 常にもがもな渚 漕ぐ 海人の小舟の 綱手かなしも
Oh, how I wish this world would never end. How wonderous to see a fisherman pull his boat along the surf.

Waka by Minamoto no Sanetomo

The image of Sanetomo that has developed as a result is one of a figurehead shogun retreating to the world of poetry and devoted to a far-off nobility. Many see Sanetomo as focusing on these more esoteric subjects as a way of coping with the stress of life under the thumb of the Hojo Clan. Indeed, Sanetomo would even pen poems while in hiding during the brief 3-day “Wada War” that broke out in Kamakura in 1213. But poetry was not the young shogun’s only cultured calling.

Sanetomo alongside calligraphy of his famous waka poem.

The Pious Shogun

Like many Japanese leaders of the era, Sanetomo also sought to use Buddhist piety to shore up his authority and prestige. He felt a special connection to the semi-legendary Prince Shotoku, a member of the Japanese court from six centuries earlier. Shotoku had been a major proponent of Buddhism, and by Sanetomo’s time was venerated as a saint. Sanetomo saw something of Prince Shotoku in himself, and the official Kamakura history, the Azuma Kagami, details many events in Sanetomo’s life that seem to purposefully echo the legendary tales of the Prince.

Yosai, head priest of Jufuku-ji Temple, played a major role in spurring on this veneration. His temple,Jufuku-ji, had originally been founded in 1200 by Sanetomo’s mother Masako in honor of Sanetomo’s father, who had died falling from a horse the year previous. Yosai was a learned monk, having traveled twice to far-off China for training. He taught the young shogun the Buddhist scriptures from the time he was 14, instilling in him veneration and yearning to visit the holy places in far-off China and even more distant India.

Dreams of a Distant Land

The relationship between the two went beyond mere teacher and pupil. It had a metaphysical quality as well. Later chronicles referred to Yosai and Sanetomo as “master and disciple across many lives,” reborn time-and-again in China and Japan, linked by a shared destiny. Sanetomo once dreamt he flew to China, where he came to learn he was the reincarnation of a great priest; when he confided this dream to Yosai, the monk claimed he’d had the same dream himself.

Discussions with Yosai and a Chinese monk, Chin Wakei, who also claimed he recognized Sanetomo as a reincarnated Chinese religious leader, spurred Sanetomo to a belief in a spiritual destiny. He sought to cross the sea to China, hoping to visit the storied Buddhist sites he believed himself directly connected to. Such a voyage would not only fulfill him spiritually, but would shore up his legitimacy as shogun when he returned bearing priceless Buddhist relics. To this end, in 1217, he ordered the construction of a massive seafaring vessel to bear him to the Asian mainland. His uncle, Hojo Yoshitoki, was firmly against the potentially dangerous venture. Sanetomo’s zeal spurred him onwards nonetheless.

Sanetomo watched on from the Yuigahama coast as the completed boat made its maiden test voyage. But the grand boat proved unseaworthy; before long, the vessel sunk beneath the waves. Sanetomo’s dreams were deferred.

In that same year, Sanetomo’s nephew, Kugyo, returned from Kyoto at long last. Sanetomo would not have to wait long for his next reincarnation.

A large, angular wooden ship, build on the orders of Minamoto no Sanetomo, is pulled out to sea by many men in period clothing.
Sanetomo’s great boat, as portrayed in the NHK drama 13 Lords of Shogun (2022).

Death of the Shogun

Kugyo had been living at the great temple complex of Onjo-ji at the foot of Mt. Hiei, far away from the capital his father, Yoriie, briefly ruled. Once second-in-line to become shogun himself, Kugyo was forced into taking monastic vows at the age of eleven. Not long after, he departed for Onjo-ji Temple, near the shore of massive Lake Biwa. The temple was one of the great centers of Tendai Buddhism, a highly ascetic, spiritually and physically demanding variation of the religion patronized by the imperial court.

Now, Kugyo was returning home for the first time in seven years. Having reached eighteen, his grandmother, Masako, felt it was time for him to take his place in Kamakura, where he could be close at hand. She arranged for him to become the new head priest of Tsurugaoka Hachiman Shrine, a great honor. No sooner had he assumed the mantle of high priest than he began an extreme, one thousand day period of self-isolation and prayer inside the shrine precinct. Kugyo shut himself away from the world.

That is, until the night of January 27th, 1219.

Late that evening, Sanetomo emerged from Tsurugaoka Hachimangu, freshly proclaimed Minister of the Right. With this imperial title, he’d achieved something even his father hadn’t. This had come following his mother’s return from a visit to the court in Kyoto. With Nobuko not yet having born Sanetomo an heir, Masasko had helped convince the court to supply one themselves. Sanetomo’s relationship with the nobility he so idolized was more solid than ever.

As he left the shrine, Sanetomo, likely elated, may have little felt the absence of his nephew Kugyo, who had locked himself away inside the shrine for months.

But Kugyo was there, watching, as the shogun began his descent down the shrine stairs. The monk rushed forward amidst the falling snow. A few acolytes appeared, overwhelming Sanetomo’s only guard. Moments later, Minamoto no Sanetomo was dead. He was only 26 years old. His dreams of journeying to China, of strengthening the shogunate, died with him. His own nephew had killed him. The question is, why?

Shogun Minamoto no Sanetomo descends the  snowy steps of Tsuruoka Hachimangu Shrine, while Kugyo lies in wait behind a tree.
Kugyo lies in wait for Sanetomo. Print by Utagawa Kokunimasa, Meiji era.

The Would-Be Shogun

Both the Gukansho and Azuma Kagami, historical records from the Kamakura period, agree that Kugyo declared his intentions as he rushed for the kill. “With this, I avenge my father!” The murderous act came following months in pious isolation; praying, perhaps, for the downfall of his uncle, Sanetomo. For the courage, perhaps, to carry out what soon proved to be his final act.

For long centuries, observers have seen the hand of the Hojo family lurking behind the assassination of Sanetomo. The Hojo were no strangers to murderous plots, and Hojo Tokimasa had conspired to kill Sanetomo only a decade earlier. And yet, Sanetomo’s mother, Masako, and uncle, the regent Yoshitoki, had little reason to want Sanetomo dead. He was cooperative and relatively pliable, his zeal for religion and the imperial court notwithstanding. Sanetomo agreed with his mother and uncle regarding how to source a shogunal heir. The three were working towards that goal at the time of the murder. The Hojo siblings had even previously intervened to save Sanetomo’s life, facing down their powerful father to do so.

Kugyo’s final acts lead us to believe he thought the murder of his uncle would result in his ascension to shogun. Certainly, he had a claim, given his late father’s position. Had someone convinced him this would be possible?

Kugyo in action.

Kugyo Flees

Having slain Sanetomo, Kugyo picked up his uncle’s detached head and fled to an outbuilding of the shrine. He quickly sent off a message to someone he thought an ally: the powerful Kamakura vassal Miura Yoshimura. Yoshimura’s wife had been Kugyo’s wetnurse, and his son was Kugyo’s disciple. Their relationship was close, and Kugyo seems to have thought they would act to support him. His message read: “Now, I am truly the great Shogun of the Kanto. Make yourselves ready.”

Miura Yoshimura immediately sent a message back, telling Kugyo to wait until he could send someone to bring him to the Miura residence. With Kugyo now delayed, Miura sent another messenger to inform Hojo Yoshitoki of the shogun’s murder. Yoshitoki immediately commanded Miura to execute Kugyo for his great crime; Miura dispatched one of his stoutest warriors, Nagao Sadakage, a veteran of the Genpei War, to carry out the deed.

Meanwhile, Kugyo had grown tired of waiting. He began climbing the hills behind Tsurugaoka Hachimangu, trudging through the snow towards the Miura residence. Nagao and his posse of armed samurai chanced upon Kugyo in the pathway between the shrine and the mansion. The assassin fled, with Nagao and his men hot on his heels. Reaching the gate of the Miura residence, Kugyo desperately attempted to surmount it. Nagao struck out at the back of his neck as he was lifting himself over, and the would-be shogun fell. Kugyo died only hours after his uncle.

The Miura’s quick betrayal of Kugyo seems to point to a lack of prior involvement in the plot. Clearly involved, however, were the monks who are said to have assisted him with the assassination. These are assumed to have been disciples of Kugyo, and, indeed, the shogunate quickly sent samurai to attack Kugyo’s residence at the shrine, where they routed the former head priest’s disciples.

So, it appears that Kugyo plotted the assassination of his uncle on his own, and involved a few disciples in a quest to retake the shogunal office that was his by birthright. He achieved the murder but lost all else. With his death, the line of Minamoto no Yoritomo came to an end. The Hojo would continue to rule as regents with a series of imperial-sourced puppet shoguns as their figureheads. But the story doesn’t entirely end there.

The Jōkyū War

The shock of Sanetomo’s sudden death reverberated all the way to Kyoto. There, the retired emperor Go-Toba most deeply felt the change Sanetomo’s death had wrought. Sanetomo had been a reliable subject of the empire, embodying the idea that the shogun existed to serve his imperial sovereign. Sanetomo had even penned a poem to that effect:

Though the time come
When the mountains split asunder
And the seas drain dry,
I shall never show my lord
A double-dealing heart.

Minamoto no Sanetomo, translated by R. H. Brower and Earl Miner. Sourced from Brownlee, J. S. (1969).

With Sanetomo dead, the shogunate in Kamakura was now a different beast. Go-Toba refused to send an imperial price to serve as Sanetomo’s heir, as “…he now saw a shogun of the imperial blood as a hostage rather than as a useful puppet.” [4] Go-Toba viewed the Hojo family as usurpers and untrustworthy, resenting the power they’d wrested from the ancient imperial regime. He proclaimed Yoshitoki an outlaw, and launched a war against the shogunate.

This was the Jōkyū War of 1221 (承久の乱), which marked the final attempt by the imperial family to prevent the rise of the samurai to permanent control of Japan. Go-Toba called upon the samurai clans, urging loyalty to his ancient regime, while in far-off Kamakura, Hojo Masako gave an impassioned plea to her closest generals to help defend the new government they’d created. In the end, the samurai chose the Kamakura government, which more directly benefited their class desires.

The war was brief. The Hojo won a decisive victory, their army pushing through to Kyoto in a three-pronged invasion. The deadliest battle was fought at the Uji bridge that guarded the southern approach of the city. The victorious Hojo sent Go-Toba into exile along with his heirs; he spent the rest of his life on the remote Oki Islands. The Hojo would rule from Kamakura for another century, and a samurai government would hold power in one form or another until 1868, more than 600 years later.

Sanetomo would have wept.

All That Remains

In the hills that surround Kamakura lie thousands of man-made caves. Known as yagura, these caves are a peculiar facet of Kamakura culture, left behind to us after eight hundred years. These yagura, dotted along the Kamakura landscape like pockmarks, were graves and honorary cenotaphs to the samurai dead.

Not far from Kamakura Station, Jufuku-ji Temple, founded in the year 1200 by Hojo Masako to honor her recently fallen husband Yoritomo, plays host to numerous yagura in its vast graveyard. One amongst these is dedicated to Masako herself; another to her assassinated son, Sanetomo. Neither contains their ashes, originally interred at Chōshōjū-in, and, like that temple itself, lost to time.

Sanetomo’s remains are gone, ashes in the wind. Just as we may never know their location, we may never know exactly why Kugyo killed his uncle. Was it an act of pure internecine revenge? Or was it a planned assassination, spurred on by the machinations of the Hojo? Either way, it was an act of kinslaying, someone of his own family consigning Sanetomo to an early death. Sanetomo never made it to China. And now only the steps of Hachiman Shrine, and an empty grave, remain to remind us of the life and death of the final Minamoto shogun.

What to read next


[1] Kobayashi Naoki. (2010.) Dreams of Sanetomo: His Portrait in the Azuma Kagami and the Legends of Prince Shōtoku. UrbanScope Vol.1, 19-33

[2] Mass, J. P. (1993). The Missing Minamoto in the Twelfth-Century Kanto. Journal of Japanese Studies, 19(1), 121–145.

[3] Mulhern, Chieko Irie. (1991. ) Heroic with Grace: Legendary Women of Japan. Routledge

[4] Brownlee, J. S. (1969). The Shōkyū War and the Political Rise of the Warriors. Monumenta Nipponica, 24(1/2), 59–77.

[5] 濱田 浩一郎. (2022/09/11). NHK大河ドラマですべては描かれない…3代将軍・源実朝を殺害した犯人のヤバすぎる動機. PRESIDENT Online.

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Noah Oskow

Serving as current UJ Editor-in-Chief, Noah Oskow is a professional Japanese translator and interpreter who holds a BA in East Asian Languages and Cultures. He has lived, studied, and worked in Japan for nearly seven years, including two years studying at Sophia University in Tokyo and four years teaching English on the JET Program in rural Fukushima Prefecture. His experiences with language learning and historical and cultural studies as well as his extensive experience in world travel have led to appearances at speaking events, popular podcasts, and in the mass media. Noah most recently completed his Master's Degree in Global Studies at the University of Vienna in Austria.

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