No account of the beginning of the Heian period can leave out Emperor Kammu.
In 794, Emperor Kammu moved the capital to Heian-kyo.
Born as his son, one emperor did more than perhaps any other to shape the politics of the early Heian period.
Emperor Saga, the 52nd emperor.
He reigned from 809 to 823.
His father was Emperor Kammu; his mother, Fujiwara no Otomuro.
His full brother was Emperor Heizei.
Emperor Saga’s fourteen-year reign is packed with events essential to understanding Heian-period politics.
The Kusuko Incident. The founding of the Kurodo-dokoro. The founding of the Kebiishi. The rise of Fujiwara no Fuyutsugu.
And the flourishing, centered on the court, of Chinese-style poetry, prose, and calligraphy.
Emperor Saga left an unmistakable mark on both politics and culture.
Trace his imperial line further, and it runs through Emperor Ninmyo → Emperor Montoku → Emperor Seiwa.
And it was from Emperor Seiwa’s own descendants that the Seiwa Genji would later emerge.
Emperor Saga is, in other words, a figure essential to understanding the entire political structure of the early Heian period.
1. Born a Son of Emperor Kammu
Emperor Saga was born in 786.
His personal name was Kamino (also written Kamino).
His father was Emperor Kammu; his mother, Fujiwara no Otomuro.
His maternal grandfather was Fujiwara no Yoshitsugu.
This traced back to the Fujiwara Shikike line, meaning Emperor Saga was born with deep ties to both the imperial house and the Fujiwara clan alike.
His full brother was Prince Ate.
The future Emperor Heizei.
These two brothers would later split the court in two.
2. Becomes Crown Prince-Heir to His Brother, Emperor Heizei
In 806, when Emperor Kammu died, his elder brother Prince Ate took the throne.
This was Emperor Heizei. At that time, Prince Kamino was named crown prince-heir.
Which meant: the elder brother was emperor, the younger brother crown prince-heir.
At this point, the order of succession was still perfectly intact.
But Emperor Heizei suffered from illness.
In 809, Emperor Heizei abdicated.
And the throne passed to Prince Kamino — Emperor Saga.
3. The Brother Who Abdicated Soon Returns to the Center of Politics
From here, Emperor Saga’s reign grew difficult.
Emperor Heizei stepped down and became Retired Emperor Heizei.
What is more, Retired Emperor Heizei left Heian-kyo and moved to Heijo-kyo.
Heijo-kyo was the former capital.
Which is to say, the reigning emperor was now in Heian-kyo,
while the previous emperor was in Heijo-kyo.
This was the situation that had emerged.
What is more, Retired Emperor Heizei’s former close aides gathered around him.
Chief among them were Fujiwara no Kusuko and Fujiwara no Nakanari.
4. Casting Kusuko and Nakanari as the Sole Villains Misses the Real Point
This matters enormously for understanding the Kusuko Incident.
The later, popular account leans heavily on the image of “an incident caused by Fujiwara no Kusuko and Nakanari inciting Retired Emperor Heizei.”
But looking at the actual course of events, Retired Emperor Heizei himself clearly held strong political intentions of his own.
Retired Emperor Heizei personally installed provincial inspectors and set the machinery of government in motion.
In 810, Retired Emperor Heizei issued an edict restoring the Sangi councillor posts, and his conflict with Emperor Saga’s side only deepened.
Then, in the ninth month.
Retired Emperor Heizei ordered the capital restored to Heijo-kyo.
This is what drove the conflict to its breaking point.
Which is why the Kusuko Incident is better understood not as
“an incident caused by a woman named Kusuko,”
but rather as
“a political conflict between the abdicated Retired Emperor Heizei and the reigning Emperor Saga.”
That framing is closer to the truth.
Kusuko and Nakanari were the central figures on the retired emperor’s side.
5. Emperor Saga Had Been Preparing Before the Crisis Ever Broke
What matters about Emperor Saga is that he did not simply scramble to react once the crisis hit.
The third month of 810.
Emperor Saga established the Kurodo-dokoro.
Appointed as Kurodo no To were
Fujiwara no Fuyutsugu and Kose no Notari.
This Kurodo-dokoro would grow into a vital institution, handling confidential documents as the emperor’s own close staff and taking part in relaying edicts and other important business.
And here appears a man who would go on to change the course of Japanese history.
Fujiwara no Fuyutsugu.
Even as the Fujiwara Shikike line of Kusuko and Nakanari fell politically, the Fujiwara Hokke line of Fuyutsugu grew steadily stronger.
This current would flow directly into the later regency government.
6. The Kusuko Incident — Heian-kyo Against Heijo-kyo
The ninth month of 810.
Retired Emperor Heizei ordered the capital restored to Heijo-kyo.
The risk emerged that the court’s own governing machinery would split in two.
Emperor Saga moved to counter it at once.
And he had Fujiwara no Nakanari arrested.
Nakanari was shot dead.
Kusuko took poison and ended her own life.
Retired Emperor Heizei tried to reach the eastern provinces, but could not, and returned to the Heijo Palace, where he took the tonsure.
This was the Kusuko Incident.
Through this political upheaval, Emperor Saga secured full political control.
Retired Emperor Heizei withdrew from the political front line, and the Fujiwara Shikike line suffered a heavy setback.
Meanwhile, the rise of Fujiwara no Fuyutsugu had begun.
7. What the Kusuko Incident Really Meant
Reduce the Kusuko Incident to
“an incident where Kusuko and Nakanari failed,”
and its real significance is lost.
What truly changed through this incident was the very structure of court government itself.
Through the Kurodo-dokoro, Emperor Saga built a system that placed his own close aides directly in control.
The Kebiishi, too, was established.
Against real political and security problems the ritsuryo system’s own offices struggled to handle, the court increasingly turned to ryoge no kan — offices outside the formal ritsuryo code.
Emperor Saga’s reign was also
an era of adapting the ritsuryo state to the realities of actual governance.
8. The Founding of the Kebiishi
As Heian-kyo grew, maintaining order in the capital became a serious issue in its own right.
This is what led to the founding of the Kebiishi.
A ryoge no kan office responsible for criminal investigation, arrest, and the maintenance of public order.
Where the Kurodo-dokoro developed chiefly as the emperor’s own close-aide institution, the Kebiishi addressed the real, practical problem of order within Heian-kyo.
These two institutions matter enormously for understanding the politics of the rest of the Heian period.
Emperor Saga strengthened the court’s governing capacity on two fronts at once:
the machinery close to the emperor himself, and the machinery of order within the capital.
9. The Rise of Fujiwara no Fuyutsugu
After the Kusuko Incident, it was Fujiwara no Fuyutsugu whom Emperor Saga came to rely on most heavily.
Fuyutsugu came from the Fujiwara Hokke line.
He would go on to rise all the way to Minister of the Right.
And Fuyutsugu’s own son was Fujiwara no Yoshifusa.
Yoshifusa would later become the first subject in history to serve as regent.
Which is to say:
Emperor Saga
↓
Fujiwara no Fuyutsugu
↓
Fujiwara no Yoshifusa
Tracing this line reveals exactly where the later regency government first took root.
The Kusuko Incident reshaped the internal balance of power within the Fujiwara clan as well.
From the Fujiwara Shikike to the Fujiwara Hokke.
810 was one of the turning points in that shift.
10. Emperor Saga Also Shaped Imperial Succession Directly
After the Kusuko Incident, Retired Emperor Heizei’s son and former crown prince,
Prince Takaoka, lost his position as crown prince.
Named crown prince-heir in his place was Prince Otomo.
The future Emperor Junna.
Which is to say, the Kusuko Incident was never merely an internal power struggle at court.
It was an incident that reshaped even the next line of succession itself.
Emperor Saga did not merely defend his own throne.
He fundamentally redirected the course of imperial succession that followed.
11. From Emperor Saga to Emperor Ninmyo
823.
Emperor Saga passed the throne to Prince Otomo.
Prince Otomo took the throne as Emperor Junna.
When Emperor Junna in turn abdicated, Emperor Saga’s own son, Prince Masara, took the throne.
Emperor Ninmyo.
From here, the imperial line continues as
Emperor Saga
↓
Emperor Ninmyo
↓
Emperor Montoku
↓
Emperor Seiwa.
Emperor Seiwa was Emperor Saga’s great-grandson.
12. And Onward to the Seiwa Genji
The line of Emperor Seiwa’s own descendants, demoted from imperial status and granted the surname Minamoto, became
the Seiwa Genji.
From within the Seiwa Genji emerged figures such as
Minamoto no Mitsunaka, Minamoto no Yorinobu, Minamoto no Yoriyoshi, and Minamoto no Yoshiie.
And from the Kawachi Genji branch of that line came
Minamoto no Yoritomo.
The line continues on from there.
But by holding on to the imperial line of
Emperor Saga → Emperor Ninmyo → Emperor Montoku → Emperor Seiwa → the Seiwa Genji,
the connection between the early Heian imperial house and the later warrior clans comes into clear view.
13. Emperor Saga Also Produced a “Genji” Line of His Own
Also crucial here is the Saga Genji.
Among Emperor Saga’s own sons were some who were demoted from imperial status and granted the surname Minamoto.
A growing imperial family placed real strain on court finances.
Which is why moves progressed to demote some members of the imperial family to subject status, granting them the Minamoto surname.
This is how
the Saga Genji came into being.
The surname Minamoto, which would later carry such enormous weight in the world of the warrior class, was originally a name given to people demoted from the imperial family itself.
“Minamoto = warriors from the very start” is
simply not accurate.
This is an important point for understanding Japanese history correctly.
14. Emperor Saga’s Other Face — the Statesman
Everything so far paints Emperor Saga as a thoroughly political figure.
And indeed, his presence as a statesman was enormous.
But Emperor Saga had another face entirely.
Emperor Saga the man of letters.
Emperor Saga loved Chinese-style poetry and prose, and composed such poetry himself.
And at court, Tang-style culture flourished on a grand scale.
Representative anthologies of Chinese-style poetry and prose from this era include
the Ryounshu and the Bunka Shureishu.
Materials from the Agency for Cultural Affairs likewise place Emperor Saga, alongside Kukai and Tachibana no Hayanari, among the “Three Great Brushes” of the early Heian period.
15. Emperor Saga, Kukai, and Tachibana no Hayanari — the Three Great Brushes
Emperor Saga was also known as a master calligrapher.
In later ages,
Emperor Saga, Kukai, and Tachibana no Hayanari
came to be known as the Sanpitsu, the “Three Brushes.”
That said, care is needed before treating every surviving work attributed to him as unquestionably “in Emperor Saga’s own hand.”
Even the Cultural Heritage Online database maintained by the Agency for Cultural Affairs carefully distinguishes, for works traditionally attributed to Emperor Saga, between traditional attribution and confirmed authenticity.
What can be said with confidence is that Emperor Saga held a deep personal interest in calligraphy.
And among his surviving works whose authenticity is firmly established, the most important is
the Kojo Kaicho.
A document Emperor Saga issued in 823 to Kojo, a disciple of Saicho, it remains a vital source for understanding what Emperor Saga’s own calligraphy actually looked like.
16. Cultural Exchange with Kukai
Under Emperor Saga, Kukai also became a central figure of court culture.
After returning from Tang China, Kukai devoted himself chiefly to esoteric Buddhism.
Emperor Saga recognized Kukai’s talent, and Kukai came to hold an important place within court culture as well.
With Emperor Saga’s own love of Chinese-style poetry and calligraphy, Tang-style culture blossomed magnificently under his reign.
The culture that took shape in this era became the foundation of what is known as the Konin-Jogan culture.
17. Emperor Saga and the Konin Kyakushiki
Emperor Saga’s reign also saw the ritsuryo system reworked to better fit the realities of governance.
The representative achievement here is
the Konin Kyakushiki.
Kyaku were supplementary edicts that amended and corrected the ritsuryo code.
Shiki were the detailed regulations for putting the ritsuryo code and its kyaku into actual practice.
The ritsuryo system, in place since the Nara period, had drifted further and further from reality as time went on.
Under Emperor Saga, legal reforms moved forward to close that gap.
Which means Emperor Saga was
not simply an emperor who upheld the ritsuryo code, but one who actively readjusted the ritsuryo state to match reality
as well.
18. The Shinsen Shojiroku Also Dates to This Era
Emperor Saga’s reign also saw the compilation of the Shinsen Shojiroku.
This vital source organized the genealogies and origins of the clans living in the Kinai region.
It remains an extremely important resource for understanding the genealogical relationships between the imperial house and the great clans and nobility.
It shows that the court of this era was actively organizing information on
“who belonged to which clan, and what their origins were.”
19. Did Emperor Saga Create the “Finished Form” of the Heian Period?
It was Emperor Kammu who moved the capital to Heian-kyo in 794.
But if we look instead for the era in which court government centered on Heian-kyo actually stabilized,
Emperor Saga’s reign becomes enormously important.
Emperor Kammu had tried to build a new capital and a new state structure.
Then, after the interlude of Emperor Heizei’s reign, Emperor Saga readjusted the political system.
He established the Kurodo-dokoro, set up the Kebiishi, and reformed the legal system.
At the same time, court culture flourished on a grand scale.
Which is why it helps to think of it this way:
if Emperor Kammu was “the emperor who began Heian-kyo,” Emperor Saga was “the emperor who gave shape to Heian-period politics and culture.”
20. Emperor Saga’s Later Years
Emperor Saga abdicated in 823, becoming a retired emperor.
He died in 842, at fifty-seven.
After Emperor Saga’s death, conflict over the imperial succession surfaced once again.
In that same year, 842, the Jowa Incident broke out.
Prince Tsunesada, Emperor Saga’s own son, lost his position as crown prince, and Tomo no Kowamine and Tachibana no Hayanari, among others, were punished.
Which is to say, the imperial line and the political order Emperor Saga had built continued to shape the court’s power struggles long after his own death.
Summary — Emperor Saga Was More Than “the Victor of the Kusuko Incident”
Emperor Saga was born a son of Emperor Kammu.
His elder brother was Emperor Heizei.
In 809, he took the throne when his brother abdicated in his favor.
But Retired Emperor Heizei retained his political influence and moved to Heijo-kyo.
And then, in 810.
The conflict between Retired Emperor Heizei and Emperor Saga escalated into
the Kusuko Incident.
Fujiwara no Nakanari was shot dead, and Fujiwara no Kusuko took her own life.
Retired Emperor Heizei took the tonsure.
Emperor Saga had won this political struggle decisively.
But what truly matters is everything that came after.
Emperor Saga established the Kurodo-dokoro.
He founded the Kebiishi. He advanced legal reform through works such as the Konin Kyakushiki.
He relied heavily on Fujiwara no Fuyutsugu, laying the political groundwork for the rise of the Fujiwara Hokke line as well.
And on the cultural side,
he loved Chinese-style poetry, prose, and calligraphy, and was later celebrated, alongside Kukai and Tachibana no Hayanari, as one of the “Three Brushes.”
Under Emperor Saga’s reign, the Tang-style culture that would come to define the Heian period truly blossomed.
Trace his imperial line further, and it continues on to
Emperor Saga
↓
Emperor Ninmyo
↓
Emperor Montoku
↓
Emperor Seiwa
↓
the Seiwa Genji.
And trace the Fujiwara clan, and it leads to
Emperor Saga
↓
Fujiwara no Fuyutsugu
↓
Fujiwara no Yoshifusa
↓
the regency government.
Which is to say, Emperor Saga was
the emperor who won the Kusuko Incident,
the emperor who built the political institutions of the Heian court,
a leading figure of Konin-era culture, and
an emperor essential to understanding the later histories of both the Fujiwara Hokke and the Seiwa Genji.
The history of Heian-kyo, begun in 794, took on much of its lasting shape under Emperor Saga’s reign.
One of the men who took the Heian-kyo that Emperor Kammu had founded and firmly established it as the center of politics and culture.
That man was Emperor Saga.
