In the first year of Chogen (1028), a warrior in Boso became the target of a court subjugation campaign.
Taira no Tadatsune.
Tadatsune had built an enormous power base across Kazusa and Shimosa, powerful enough that even a provincial governor’s orders could not easily reach him. When the Governor of Awa burned to death and the Kazusa provincial headquarters fell under his control, the court dispatched a commander to subdue him.
Yet Tadatsune kept up his resistance for roughly three years.
The man finally appointed as commander was Minamoto no Yorinobu.
And then Tadatsune did not fight. He took religious vows and, accompanied by his two sons and three retainers, presented himself before Yorinobu in Kai on his own initiative.
Why did a man who had defied the court’s armies submit to Yorinobu instead?
Following that answer reveals not only the figure of Taira no Tadatsune, but how warriors of the eleventh-century east lived, whom they bonded themselves to, and how they accumulated power.
And Tadatsune’s story does not end with his defeat in 1031.
His bloodline remained in Boso, leading to the later Chiba and Kazusa clans.
Roughly 150 years later, Tadatsune’s descendants would support Minamoto no Yoritomo and play a role in founding the Kamakura shogunate.
967 — born as a grandson of Taira no Yoshifumi
Major biographical dictionaries record Taira no Tadatsune’s birth as the fourth year of Kōhō (967).
His father was Taira no Tadayori. His grandfather was Taira no Yoshifumi.
Yoshifumi was a son of Prince Takamochi, great-grandson of Emperor Kanmu, and a Kanmu Taira warrior who spread his power across Bando.
Tracing the lineage:
Emperor Kanmu
↓
Prince Katsurabara
↓
Prince Takamochi
↓
Taira no Yoshifumi
↓
Taira no Tadayori
↓
Taira no Tadatsune.
Among the other descendants of Prince Takamochi was Taira no Masakado, struck down in the third year of Tengyo (940) (his rebellion is covered in this article — Japanese only).
Tadatsune, like Masakado, was an eastern warrior descended from the same Kanmu Taira line.
That said, Tadatsune was born 27 years after Masakado’s death. In the Bando where Tadatsune grew up, the memory of Masakado’s rebellion still lingered, but the balance of power among the warriors had already moved into its next stage.
Governors continued to arrive from Kyoto, but on the ground stood powerful men whose families had put down roots there over many generations. They involved themselves in the provincial government offices, managed land, commanded retainers, and held military force of their own.
Tadatsune was born into that world.
“Taira against Taira” — a rivalry continuing since his father Tadayori’s own generation
Understanding Tadatsune’s life requires knowing the era of his father, Tadayori.
The Kanmu Taira of Bando were never a single, unified body.
While Yoshifumi’s line spread its power into Musashi and Shimosa, the line descending from Taira no Sadamori — the man who struck down Masakado — along with his uncles and younger brothers, was also growing in strength centered on Hitachi.
In the first year of Kanna (985), Tadatsune’s father Taira no Tadayori and his younger brother Tadamitsu came into conflict with Sadamori’s younger brother, Taira no Shigemori.
According to a Council of State edict preserved in the Zoku Sajosho, when Shigemori attempted to dedicate 600 scrolls of the Great Wisdom Sutra to Enryaku-ji Temple, the conflict with Tadayori and Tadamitsu’s side became a serious matter, to the point that an edict for their subjugation was even issued.
Tadatsune was around 18 at the time.
In other words, from a young age, Tadatsune had already witnessed the reality that even within the Bando Taira, land, connections, and spheres of power were fiercely contested among relatives.
This rivalry carried forward roughly 40 years, into the rebellion of Taira no Tadatsune itself.
Taira no Naokata, ordered to subdue Tadatsune first, was a warrior of the Sadamori line.
The conflict between Tadatsune and Naokata carried, alongside the framework of court versus rebel, the additional layer of a struggle for supremacy between the Yoshifumi and Sadamori lines.
(A full profile of Taira no Naokata is available in English here.)
From a base in Soma District, Shimosa, expanding into Kazusa and Shimosa
Tadatsune further expanded the eastern base inherited from his ancestors.
The Sekai Dai Hyakka Jiten identifies Tadatsune’s ancestral base as Soma District, Shimosa Province, from which he expanded his holdings into Kazusa, Shimosa, and Hitachi.
Soma District spans the area from present-day northwestern Chiba Prefecture into southern Ibaraki Prefecture.
Tadatsune eventually became one of the most powerful warriors in all of Boso.
He is recorded as having served as Vice Governor of Kazusa, Acting Vice Governor of Shimosa, and constabulary officer of Musashi Province.
In particular, constabulary officer was a military post responsible for maintaining regional order and policing armed groups.
This is the fascinating part of Tadatsune as a figure.
A man later subjugated by the court had originally held a post responsible for defending regional order.
Tadatsune was no bandit chieftain divorced from the court’s provincial administration.
He was a warrior who grew too large for the very system he was embedded in, even as he remained tied to the provincial government’s own structure.
The “man who moved Kazusa and Shimosa entirely as he wished,” as preserved in the Konjaku Monogatarishu
What vividly conveys Tadatsune’s enormous power is the later Konjaku Monogatarishu.
There, Tadatsune is depicted as a man with a large private army, moving Kazusa and Shimosa entirely as he wished, treating his public duties lightly, and paying no heed even to the provincial governor’s orders.
As a work of narrative fiction, its details cannot be treated as a straightforward contemporary record. Even so, it makes clear that Tadatsune was remembered by later generations as “a great warrior even a provincial governor could not easily move.”
What sustained Tadatsune’s power was never martial prowess alone.
He held land, commanded retainers, held connections within the provincial government, and bonded himself to local powers.
A governor from Kyoto left once his term ended.
Tadatsune’s family remained on the land.
That difference became an enormous source of political power in the eleventh-century east.
Tadatsune’s base — traditions surviving at Otomo, Soma, and Oshii
Various traditions arose in later generations concerning Tadatsune’s home base.
These include Otomo in present-day Tono Town, Katori District, Chiba Prefecture, Soma District in Shimosa Province, and Oshii, a place later connected to the Chiba clan.
Official materials from Chiba City describe Tadatsune as having wielded his power over Kazusa and Shimosa from a base including Otomo Castle.
That said, the medieval castle remains surviving today cannot simply be equated with a residence from Tadatsune’s own time. The castle ruins at Oshii, for instance, are considered archaeologically to date from the latter half of the sixteenth century.
A biographical account is best kept clear of conflating the two.
What can be said with confidence about Tadatsune’s own time is that he was never a lord confined to a single castle, but a warrior with power spread across multiple regions of Kazusa and Shimosa.
Minamoto no Yorinobu — the man who would ultimately decide Tadatsune’s fate
One figure mattered in Tadatsune’s life even before the rebellion began.
Yorinobu was the third son of Minamoto no Mitsunaka, a warrior later positioned as the founder of the Kawachi Genji line.
The Konjaku Monogatarishu preserves an anecdote about Tadatsune from the time Yorinobu served as Vice Governor of Hitachi in the east.
Tadatsune was so powerful that he would not even obey Yorinobu’s orders. Yorinobu, taking only a handful of men including his son Yoriyoshi, set out for Tadatsune’s residence.
Tadatsune’s side hid their boats, blocking any way to cross the water.
But Yorinobu’s party found a shallow crossing and pressed straight on to the residence.
The tale describes Tadatsune, overcome by Yorinobu’s sheer nerve, submitting a myobu and pledging himself as his follower.
A myobu was a document bearing one’s own name, submitted to a lord as a vow of service.
This scene in the Konjaku Monogatarishu carries the embellishment typical of narrative fiction. Even so, the Nihon Dai Hyakka Zensho also regards this tale as reflecting a genuine bond of lord and vassal between Yorinobu and Tadatsune that predated the rebellion.
Here lies the background to why Tadatsune later resisted Taira no Naokata, yet surrendered to Yorinobu without a fight.
Ties to Fujiwara no Norimichi too — a Heian warrior’s “multiple lords”
Tadatsune also had a central connection separate from Minamoto no Yorinobu.
Fujiwara no Michinaga’s son, Fujiwara no Norimichi.
A mid-Heian warrior was never bound to a single lord alone, unlike a vassal of the later Sengoku-era warlords.
In the provinces, he involved himself with the provincial government and served military nobles; in Kyoto, he became a retainer of a powerful senior noble.
Holding multiple such relationships was the practical means of protecting one’s land and standing.
Even while wielding enormous power across Boso, Tadatsune also needed a political connection to Kyoto.
This relationship with Norimichi comes through clearly the moment Tadatsune became a target for subjugation in 1028.
1028 — everything changes with the death of the Governor of Awa
In the first year of Chogen (1028), Tadatsune was 62 by Japanese count.
This was not a young, hot-blooded warrior suddenly raising an army on impulse.
A seasoned warrior, who had lived nearly half a century building land and connections in the east, became the target of the court’s subjugation.
The spark was an incident in Awa Province.
The Governor of Awa, Koretada, came under attack from Tadatsune’s side and burned to death.
Tadatsune’s forces went on to seize the Kazusa provincial headquarters, subduing the side of the Vice Governor of Kazusa, Agatainukai no Tamemasa, as well.
A provincial headquarters was the administrative center handling a province’s government and tax collection.
Seizing it by force carried enormous weight.
In the sixth month of the first year of Chogen, the court decided on the subjugation of Tadatsune and his sons.
Here began the rebellion of Taira no Tadatsune, which would run for roughly three years.
This was never a rebellion “to overthrow Kyoto”
Looking at Tadatsune’s conduct, an enormous difference sets him apart from Taira no Masakado.
Masakado declared himself “the New Emperor,” attempting to build his own regime in the east.
Tadatsune never went that far.
Even while holding the Kazusa headquarters, he let tribute bound for powerful nobles in Kyoto pass through unimpeded. He further sent his retainers to the capital, explained his own position, and appealed to Fujiwara no Norimichi and others to halt the subjugation.
What Tadatsune sought was never to replace the emperor in Kyoto.
It was to bring his clash with a provincial governor to an end on terms favorable to himself, using his connections to the center.
This sensibility matters greatly for understanding the eleventh-century warrior.
Tadatsune was never a revolutionary trying to build a new state outside the court.
He was a warrior making use of the court’s own institutions and his relationships with central nobles, while trying to preserve as much independence as possible in the provinces.
The fight against Taira no Naokata — a rivalry he could not concede, precisely because they shared the same Kanmu Taira blood
The court chose Taira no Naokata as its first commander.
Naokata, too, was Kanmu Taira, but from a different line than Tadatsune.
Tadatsune belonged to the Yoshifumi line.
Naokata belonged to the Sadamori line, the line that had struck down Masakado.
Tadatsune’s father Tadayori and Sadamori’s younger brother Shigemori had already clashed in 985.
In other words, behind Tadatsune and Naokata lay a rivalry within the Taira running back to their ancestors’ own generation.
For Tadatsune, surrendering to Naokata was never merely a matter of submitting to the court.
It would also mean bowing, within the Bando Taira itself, to a rival house he had contended with for years.
In the eighth month of the first year of Chogen (1028), Naokata and his men, roughly 200 strong, departed Kyoto.
Provincial governors and local powers of the east were mobilized to the subjugation side as well.
Even so, Tadatsune did not submit.
20 to 30 mounted men into the mountains — a war fought without great decisive battles
The rebellion of Tadatsune left no record of a single enormous, decisive battle like the great engagements of later ages.
Tadatsune resisted by using his knowledge of the terrain, withdrawing into the mountains of Boso.
The Shoyuki records that Tadatsune, leading roughly 20 to 30 mounted men, withdrew into an area recorded as “Ishimiyama.”
Some believe this corresponds to the area around present-day Isumi region, Chiba Prefecture.
Rather than holding the provincial headquarters and waiting for a frontal decisive battle, he retreated into the mountains, deploying his forces as circumstances allowed.
On the twenty-seventh of the third month, in the third year of Chogen (1030), Tadatsune’s side advanced into Awa once again, and the new Governor of Awa, Fujiwara no Mitsunari, fled back to the capital, leaving behind his official seal and the keys to the provincial granary.
Even roughly two years into the rebellion, Tadatsune’s army still had strength enough to drive a governor out of his own province.
Winning, and yet the province was dying
Naokata could not capture Tadatsune.
Tadatsune, too, could not win a decisive victory.
What broke down in the meantime was Tadatsune’s own base itself.
The subjugation army requisitioned provisions and supplies from the land. Tadatsune’s side, too, needed men and food to keep fighting.
As a result, the three Boso provinces were rapidly worn down.
After the rebellion, the figures reported by Vice Governor of Kazusa Fujiwara no Tatsushige were staggering.
Before the rebellion, Kazusa’s rice paddies totaled more than 22,980 cho.
But by the war’s final stage, only a little over 18 cho remained under actual cultivation.
By simple calculation, roughly 0.08%.
These figures cannot simply be treated as modern land-survey statistics. Even so, it is clear that the court of the time recognized the devastation of Kazusa as an extraordinary crisis.
Boso itself, the very land Tadatsune was fighting to protect, was being destroyed by the long war.
1030 — taking religious vows, moving toward peace
In the third year of Chogen (1030), Tadatsune began moving to bring the war to an end.
On May 20, word reached Kyoto that Tadatsune had taken religious vows.
That same June, documents submitted from the subjugation side were also read as showing Tadatsune’s intent toward peace.
Meanwhile, Taira no Naokata had also gone roughly two years without capturing Tadatsune.
On July 8, the court decided to recall Naokata.
And in the ninth month, a new figure was chosen as commander.
The very same Yorinobu whose relationship with Tadatsune had been recorded more than twenty years before.
This appointment decided the rebellion’s outcome.
1031 — he surrendered to Yorinobu without a single battle
The fourth month of the fourth year of Chogen (1031).
Tadatsune, accompanied by his two sons and three retainers, presented himself before Yorinobu in Kai.
No great decisive battle ever broke out between Yorinobu’s army and Tadatsune’s.
A man who had resisted the court’s subjugation for roughly three years surrendered to Yorinobu without a fight.
The reasons were not just one.
Boso was already exhausted. Tadatsune himself had been seeking peace since the year before.
And Yorinobu was a man Tadatsune had already served in the past.
Surrendering to Naokata would mean bowing to a rival branch of the Sadamori-line Taira.
Surrendering to Yorinobu could instead be framed as returning to a bond of lord and vassal that already existed.
For Tadatsune, Yorinobu was the ideal figure to bring the war to a close.
Yorinobu later boasted, in a votive text to Iwashimizu Hachimangu Shrine, that he had brought Tadatsune to submission without ever raising troops in force, drawing a bow, or loosing an arrow.
Yorinobu’s victory was never simply a matter of superior military force.
He held the reputation and the bond of lord and vassal needed to bring the enemy to surrender before him.
This success dramatically elevated the reputation of the Kawachi Genji in the east.
His name after taking vows — “Joan” or “Shoan”
At the time of his surrender, Tadatsune had already taken the tonsure.
His name after taking vows is recorded differently across sources — some give “Joan,” others “Shoan.”
The Sekai Dai Hyakka Jiten and the Nihonjin Meidaijiten record “Joan”; the Nihon Dai Hyakka Zensho records “Shoan.”
Rather than settling on one, it is more accurate to note this simply as a variation across sources and dictionaries.
If born in 967, Tadatsune was 65 by Japanese count at this point.
The old warrior who had moved Kazusa and Shimosa at will finally shaved his head and submitted to a man he had once called his lord.
June 6, 1031 — dies in Mino before reaching Kyoto
Having surrendered, Tadatsune was to be escorted to Kyoto by Yorinobu.
It was to face judgment before the court.
But on June 6, in the fourth year of Chogen (1031), Tadatsune died of illness partway there, at Nogami, Mino Province.
This corresponds to the area around present-day Sekigahara Town, Gifu Prefecture.
He was 65.
Yorinobu carried Tadatsune’s head onward and entered Kyoto on June 16.
The man who had tormented the court’s subjugation army in Boso for roughly three years ended his life without ever facing judgment in the capital.
Even after Tadatsune’s death, the rebellion did not end in “the annihilation of his family”
Even after Tadatsune’s death, his sons remained in Boso.
Sources give the names Tsunemasa and Tsunechika.
At the court council of June 27, whether to subjugate Tadatsune’s sons, who had not yet submitted, was debated.
In the end, no large-scale campaign to wipe out the family took place, and Tadatsune’s descendants remained in Boso.
Here lies one of the most fascinating aspects of Taira no Tadatsune as a historical figure.
The man himself died a rebel.
But the land, the connections, and the ties to local society passed down from his ancestors did not vanish with him.
His sons and grandsons advanced the redevelopment of a Boso ravaged by war, and rebuilt their power once more.
From Tadatsune’s son Tsunemasa to the Chiba clan
Tadatsune’s descendants eventually grew into the great warrior confederation known as the Ryoso Taira.
Materials from Chiba City hold that the lineage continued from Tadatsune’s son Taira no Tsunemasa, through his descendants Tsunekane and Tsuneshige, spreading power across Kazusa and Shimosa.
On the first day of the sixth month, in the first year of Daiji (1126), Chiba Tsuneshige, a great-grandson of Tadatsune’s son Tsunemasa, is said to have moved his base to Chiba.
His son was Chiba Tsunetane.
In the fourth year of Jisho (1180), when Minamoto no Yoritomo was defeated at the Battle of Ishibashiyama and fled to Boso, Tsunetane sided with Yoritomo.
From Tadatsune’s line also grew the Kazusa clan, and Kazusa no Hirotsune joined Yoritomo’s uprising leading a great army.
Roughly 150 years after his defeat, Tadatsune’s bloodline stood at the very center of the eastern warriors who supported the Kamakura shogunate.
The 1031 surrender leads forward to 1180
What stands out most in Tadatsune’s life is that, in the end, he surrendered to Minamoto no Yorinobu.
In 1031, Tadatsune surrendered to Yorinobu.
Roughly 150 years later, Tadatsune’s descendants Chiba Tsunetane and Kazusa no Hirotsune supported Minamoto no Yoritomo, Yorinobu’s own descendant.
From Yorinobu, to Yoriyoshi, to Yoshiie.
From Tadatsune, to the Boso Taira, to the Chiba and Kazusa clans.
The bond between the Genji and the warriors of the east, born in the eleventh century, would carry forward into the Kamakura regime of the twelfth.
Taira no Tadatsune stood along the way in that long current.
He never declared himself “New Emperor” as Masakado had.
Nor did he build a new warrior government as Minamoto no Yoritomo would.
And yet, Tadatsune’s life already contains every element that would go on to shape the warrior society of later ages.
Hold land.
Command retainers.
Contend with the provincial governor.
Bond yourself to a powerful noble in Kyoto.
Submit a myobu to a military noble, forming a bond of lord and vassal.
And fight the court’s own subjugation army on ground that is your own.
A warrior who grew up within the court’s own provincial rule, and grew too large for that same rule to easily contain.
That was Taira no Tadatsune.
Twenty years after Tadatsune’s death, in the sixth year of Eisho (1051), Minamoto no Yorinobu‘s son Minamoto no Yoriyoshi and grandson Minamoto no Yoshiie set out for the Former Nine Years’ War in Oshu.
The bond between the Genji and the warriors of the east only grew stronger.
Meanwhile, Tadatsune’s own descendants were also rebuilding their power in Boso.
In 1031, the bloodline of a rebel who died in Mino did not disappear.
Ahead of it lay the age of the warrior in which Chiba Tsunetane, Kazusa no Hirotsune, and Minamoto no Yoritomo himself would live.
(The rebellion of Taira no Tadatsune is available in English here, and a full profile of Taira no Naokata here.)
