To advance not at all, and then to dismiss the troops – what kind of reasoning is there in this plan of Our generals? We know that it is because Our generals fear the ferocious rebels that they remain in garrison. They cleverly employ words to avoid facing their crimes. Nothing can surpass this in disloyalty.

Such was the verdict of Emperor Kanmu on a notorious military debacle in 789, suffered at one of the far frontiers of his realm, in north-eastern Honshū. From an imperial force claimed by court chroniclers to have numbered in excess of 50,000 men, a number of detachments had been sent across the Koromo River to attack the home territory of a ‘barbarian’ leader by the name of Aterui. The soldiers set about their task enthusiastically, managing to burn down some 800 homes spread across fourteen villages. But then things started to unravel.

Based on a Chinese model, the imperial army was organized to fight mostly on foot. They used wooden shields for protection and deployed against their enemy a combination of bows and arrows, spears, and catapult-like devices built on top of mobile platforms. Aterui’s forces, by contrast, consisted of skilled archers mounted on horseback, capable of launching volleys of arrows before galloping away out of reach. They now counter-attacked, harassing Kanmu’s men into a hasty and disorganized retreat back across the river. Nearly 300 imperial soldiers were killed or wounded in the fighting, while more than 1,000 drowned. Another 1,250 ended up fleeing the scene half-naked, having survived in the water only by letting go of their weapons and wrestling their armour from their bodies.

The whole thing was a disgrace, as far as the Emperor was concerned. Born in 737, Kanmu had ascended the throne in 781, becoming Japan’s fiftieth emperor according to the traditional line of succession going back to the mythical Emperor Jimmu. Japanese emperors tended to have a number of official consorts. It was a useful way of maintaining alliances with important clans, but a source of endless conflict over which of an emperor’s children – by which wife – would be named heir. Kanmu’s half-brother had initially been designated Crown Prince instead of him. Kanmu’s Korean ancestry on his mother’s side perhaps held him back; only later was the succession altered in his favour.

Kanmu proved to be an excellent monarch. As a former Head of the State Academy – Nara’s training centre for future officials – he was well placed to operate the levers of a centralized imperial system of government whose inspiration the Chronicles of Japan credited to the great Prince Shōtoku. And where that system was not to his liking, Kanmu found ways of working around it. With the Dajōkan, or Great Council of State, threatening to become the means by which elite clans like the Fujiwara could compromise imperial power, Kanmu dealt with vacancies there, when they arose, either by installing members of his own family or by leaving the posts empty.

This keeping of the clans at bay helped Kanmu to become one of the most powerful emperors in the archipelago’s history, a worthy contemporary of Charlemagne at the other end of the Eurasian continent. He epitomized the kind of forceful imperial leadership, seen on and off between the late 600s and mid-800s, which was capable of pushing important boundaries in a country by this time referred to in official correspondence as ‘Nihon’ (Japan). Kanmu expanded and shored up his country’s frontiers. He advanced its religious and artistic imagination, and he corralled its wealth and manpower into the establishment of its greatest city.

Alongside Kanmu’s unprecedented political and military authority ran what his chroniclers recalled as a powerful dislike of ‘literary floweriness’. Here was a man not to be failed, and certainly not to be plied with unlikely excuses or poetic protestations. Kanmu’s military commanders discovered all this to their cost in the wake of the humiliation at the Koromo River:

Government losses are nearly 3,000! What is there to be joyous about? You say, ‘Wherever the heavenly troops were sent, there were no strong enemies before them. In their homes in the caves along the sea and bays, no more will there be human smoke; in their nests and holes in the mountains and valleys only ghost fires can be seen.’ These are only floating words; they far exceed reality.

As to the sending of victory reports to court, these should be made after the rebels have been levelled and merit made to stand. Without advancing into the depths of their territory, you boast that you have destroyed their villages and rush to proclaim your joy. Is this not too shameful?

Had Kanmu’s commanders taken their leader’s preference for straight talking and forensic analysis more seriously, they might have tried a different tack in their reports – admitting failure and blaming it on the raw materials they were given to work with. Theirs was, after all, merely a conscript army. Four years in the military – one served in the capital, three on one of the frontiers – was part of the price that a man paid for the honour of being an imperial subject. The rest of the time he would farm his state-allocated plot of rice, labour on public works projects when required (up to sixty days a year), pay his taxes and behave himself.

It didn’t always make for an easy life. Population pressure on the land could be heavy. Outbreaks of famine and disease were not unknown. And conscription tended to compound economic hardship. Little of the military equipment lining the bottom of the Koromo River after 789 had been paid for out of courtly coffers. A conscript was expected to feed, clothe and equip himself on the basis of an official kit-list – including a bow, bow-strings, arrows, quiver, two swords, leggings and boots – whose proper fulfilment could easily bankrupt a family.

When it all became too much, some farmers chose to flee to the north-east of Honshū in an attempt to escape imperial reach. Others journeyed in the same direction as official colonists: they were sent by the state during the 700s as part of a boundary-pushing exercise in which new forts were established – a combination of garrison, granary and administrative centre – and farmers were required to break and till the land around them.

Both sorts of migrant ended up in conflict with the older inhabitants of this part of the archipelago. They were a mix of hunter-gatherer and agriculturalist clans, lumped together as ‘barbarians’ and ‘savages’ by a Japanese state whose approach to outsiders was yet another of its cultural borrowings from China. In the words of the Chronicles of Japan:

Amongst these savages the Emishi are the most powerful. Their men and women live together promiscuously, there is no distinction of father and child. In winter they dwell in holes, in summer they live in nests. Their clothing consists of furs, and they drink blood. Brothers are suspicious of one another. In ascending mountains they are like flying birds; in going through the grass they are like fleet wolves.

When they receive a favour, they forget it, but if an injury is done them they never fail to revenge it. Therefore they keep arrows in their top-knots and carry swords within their clothing … If attacked, they conceal themselves in the herbage; if pursued, they flee into the mountains. Therefore ever since antiquity they have not been steeped in the kingly civilizing influences.

The present trouble with these ‘Emishi’ had begun in 774, when the old policy of slow and steady colonization, combined with some judicious alliance-making, was brought to an end by an imperial order to ‘strike down the barbarians’. Emperor Kanmu inherited the resulting conflict, its painfully slow progress and even more painful costs becoming the bane of his early reign.

A small victory was won in 801–2, when a new military commander by the name of Sakanoue no Tamuramaro managed to put sufficient pressure on Aterui to persuade him and another prominent Emishi leader to negotiate their surrender. But where Emishi prisoners taken in this way were usually dispersed across Japan, serving as slaves of the nobility or living in their own segregated communities, these two high-profile prisoners ended up losing their heads. Kanmu and his advisers had had enough of the north.

A few years later, Kanmu ended the Emishi campaigns altogether, reluctantly allowing parts of north-eastern Honshū to remain beyond his reach. The fighting had become one of two great ‘sources of suffering in the realm’, as one of his advisers put it. The other was the new capital city growing up around them.

Almost immediately upon ascending the throne in 781, Kanmu had decided to transfer his court to a new location. In the past, emperors had moved around for a variety of reasons. Some thought that a new era should begin in a new place, and ideally in a more impressive palace than their predecessor: this was a matter not merely of self-regard, but of advertising one’s role as the ‘sacred centre’ of the realm. Others found themselves facing a famine or epidemic, and sought to escape this combination of physical threat and spiritual contagion by upping sticks – literally, in terms of valuable timber structures, which could be taken down and reassembled elsewhere. Semi-regular uprisings by armed rivals offered a third compelling rationale for a hasty relocation.

Kanmu, in the end, found himself having to move home not once but twice. He first transferred his court from Nara to an area called Nagaoka, in 784. But it was quickly beset by political assassination, suicide, famine, flood and disease, persuading Kanmu to seek out a more auspicious location. This he did on horseback in 793, under cover of a ‘hunting trip’ on which he was joined by his royal diviners.

They found what they were looking for around fifty kilometres north of Nara. The topography ticked all the boxes. There were mountains to the north, west and east, offering excellent defensive potential. Chinese geomantic requirements for pleasing the gods of the four quadrants were also met: a mountainous north, a roadway to the west, a river to the east, and a large area of water to the south. The inauspicious north-east, from which it was said demons might invade, was guarded by the formidable Mount Hiei. Added to all this was rich, naturally irrigated rice-growing soil, timber aplenty in the hills, good access via river to the Inland Sea (separating the islands of Honshū, Shikoku and Kyūshū), and a generally flat central area on which to build without too much preparatory work required.

If there was a catch, it was the climate. The site was located in a basin, meaning that summers and winters would not be much fun for residents: alternating intolerably hot and humid weather with bitter cold. Kanmu endured his own first winter there in 794. From the confines of a palace that was still under construction, he issued a grand edict announcing the new location for the imperial capital alongside his choice of official name. It was to be called Heian-kyō: ‘Capital of Peace and Tranquillity’. Most Japanese would one day know it simply as ‘Capital City’ – in Japanese, ‘Kyoto’.

A city destined to be home to Japan’s emperors for more than a thousand years started life on a relatively modest scale. A rectangular-shaped grid ran for five and a half kilometres from north to south, and nearly five kilometres from east to west. Wide avenues ran along both axes, paralleled by narrower lanes in between. Most buildings were limited to a single storey, meaning that residents suffering with the climate could at least claim the consolation of fantastic views – lush, forested mountains, whose seasonal changes of colour became a favourite theme for the writers who soon flourished in Kanmu’s new capital.

And this really was Kanmu’s capital. The north end of Heian-kyō was dominated by a ‘Greater Imperial Palace’ that sprawled across nearly 7 per cent of the city’s total land area, and whose construction, alongside that of associated princely residences, accounted for up to three-fifths of central government expenditure during Kanmu’s reign. Provincial workers, here to pay their imperial labour tax, were kept busy erecting around 200 buildings, towers and corridors – including fourteen separate gateways, of which the most important was the Suzakumon: the ‘Gate of the Vermilion Sparrow’.

This was both the Emperor’s home and his place of business. A residential compound was located at the north end of the palace complex, while government offices and meeting areas, including the three buildings that comprised the Great Council of State, were laid out to the south. A large area of greenery, the ‘Park of the Divine Spring’, was maintained nearby for imperial banquets, entertainment and the occasional spot of hunting and fishing.

Southwards from the palace, all the way through the city, ran Suzaku Ōji. Possibly the broadest boulevard in the world at the time at around ninety metres wide, and terminating in the famous Rashōmon gate (two storeys high and painted red and white with a green roof), it was lauded in song for its beautiful willow trees:

Light green they shine,

Dark green they shine,

Stretching into the distance as far as the eye can see,

They glitter like jewels.

Oh, how they glitter – those low-hanging boughs

Of the willows on Suzaku Ōji!

In the centre of the city lay two shopping areas, where business was based mostly on barter and items for sale included everything from rice and fruit to writing brushes, medicinal herbs and suits of armour. Fine accommodation was created for visiting foreign dignitaries, in the hope of striking favourable trade deals, while aristocratic residents settled into expansive villas whose exquisitely kept gardens and ponds were fed from the city’s waterways – so numerous that Heian-kyō quickly became home to hundreds of bridges. Most of the population, estimated at around 100,000 people in the city’s early years, lived rather more modestly and were involved, directly or indirectly, in some kind of service to the state and the aristocratic class: from keeping accounts and guarding prisoners to brewing sake, weaving silk and reviving heat-stricken humans or their pets.

Heian-kyō had no perimeter wall worthy of the name, because Kanmu had no earthly enemies worthy of the name. Concerned instead with cosmic vulnerability and defence, he was quick to send tributes to the Upper and Lower Kamo Shrines, situated in the feared north-easterly direction, in order to seek the protection of the kami enshrined there. This offering of tributes soon morphed into an annual night-time ceremony in which priests called out to the gods in darkness, bidding them to come down into specially created structures of sand and pine logs. From there, the kami were transferred into small sakaki trees, to be carried into the main sanctuary of the shrines. This accomplished, the shrines were illuminated and public festivities were held for the kami’s amusement.

These festivities grew in scale, year on year, until the Kamo Festival became the major event in Heian-kyō’s social calendar. A Grand Imperial Emissary and a specially selected imperial princess would travel to the two shrines, the former to present tributes including dances and horses, and the latter to worship there – just as a member of the imperial family worshipped at Amaterasu’s Ise Shrine, to whose level the Kamo Shrines were now elevated. Both the emissary and the princess travelled with glamorous retinues. Senior courtiers rode on horseback or rumbled along inside ox-drawn carriages lavishly adorned with hollyhock flowers, accompanied on their journey by musicians and dancers. The whole city turned out to watch the spectacle, with vantage points varying according to the decorum demanded by one’s status. The higher-born sent someone ahead to save a good parking spot for their carriages. Humbler sorts roamed rooftops and the branches of tall trees.

Solicitous of the kami, Kanmu was rather more sceptical about the role that Buddhism might play in the welfare of his city and his country. One of the reasons for leaving Nara behind after he became Emperor had been its powerful, even overbearing Buddhist institutional presence: from great temples, grown wealthy and excessively independent of imperial and clan patronage, to a population of monks so large that Kanmu’s father had striven to weed out any who were living in the capital illegally and have them returned to the provinces whence they came. If rival clans were one perpetual threat to imperial power, Buddhism had come to represent a second. And Kanmu was determined to do something about it.

One of Buddhism’s most powerful backers after Prince Shōtoku had been Emperor Shōmu (reigned 724–49). A mixture of personal devotion and desperate pragmatism, in the midst of a devastating smallpox outbreak in 735–7, had led him to establish a protective nationwide network of temples and nunneries: one of each, in every province. The awesome Tōdai-ji in Nara was built to serve as the central temple for this network and as home to an enormous sixteen-metre gilded bronze statue of the celestial Buddha Vairocana. Its casting, said to have required 338 tons of copper and 16 tons of gold, nearly drove the nation into bankruptcy. The statue’s dedication in 752, during which its eyes were ceremonially opened, had been one of the events of the era, attended by no fewer than 7,000 courtiers and 10,000 monks.

Alongside keeping the country safe and furnishing some of its great early aesthetic achievements, Buddhism also became a way for talented individuals born into families of modest means to acquire education and enter public service. Some outstandingly wise and compassionate figures emerged in this way, amongst them a monk by the name of Gyōki (668–749) who was celebrated for his preaching and his practical aid to poor farmers – notably a number of precious irrigation projects – alongside his work as an imperial adviser.

Yet some clergy seemed to treat Japan’s legal restrictions on monastic behaviour – from taking wives to lending money and holding private property – less as a series of prohibitions and more as a to-do list. Temples loaned money to farmers, then took their land when they defaulted on repayments. One temple was said to be operating as a pawnbroker, charging an annual interest rate of 180 per cent. The biggest fear was of monks playing politics, potentially giving rise to an anti-imperial perfect storm of eloquent preaching, deeply impressive ideas and vestments and rituals, hostile clan backing and popular discontent about the direction in which the world was heading. This had yet to happen, but in the 760s a mercurial monk called Dōkyō had managed to persuade Emperor Shōmu’s daughter and successor to grant him progressively greater influence in government. Amidst rumours of intimacy with the Empress, he eventually sought the throne itself, thwarted in the end only by vehement courtly opposition and by the Empress’s death.

Kanmu fought back against all this on several fronts. He banned the establishment of ‘private temples’, a practice that was often less about devotion than tax-avoidance: institutions claiming to conduct rituals for the good of the realm were exempt from contributing to its coffers. And he banned existing temples from receiving donations without permission. At the same time he opened up temple property to provincial audits (and possible confiscation), and set the maximum interest rate for a temple loan at a comparatively reasonable 10 per cent. Kanmu clamped down, too, on clergy fathering children, claiming to be able to work miracles and engaging in ‘black magic in the mountains with the aim of harming their enemies’. All the while, he tried to raise the bar for people wishing to become monks or nuns. Character and learning were given renewed importance, the latter tested via rigorous examination.

But Kanmu’s most consequential move was the one he made against the supremacy of the Buddhist establishment in Nara, which was made up of six major sects. In this he was helped by a monk called Saichō. Born in 767 and ordained at Tōdai-ji in 785, Saichō swapped what he saw as the corruption of contemporary Buddhism for an austere life on Mount Hiei – a rare move in his day. When Kanmu moved his capital to the area in 794, he came to hear of Saichō’s life on Hiei and his study of Tiantai Buddhism. Struck by the potential of the latter as an alternative to the squabbling Nara sects, Kanmu allowed Saichō to travel to China to learn more.

Saichō arrived in China in 804, returning to Japan the next year having studied these and many other Buddhist teachings besides. The result, within a few short years, was a new ‘Tendai’ sect, established on Mount Hiei and taking its name from ‘Tiantai’ while in fact being very much more. It incorporated elements from Zen, from a set of advanced moral codes called the Bodhisattva Precepts and from esoteric Buddhism. Tiantai by itself was already an attempt to work Buddhism’s various sects and scriptures into an ambitious hierarchical whole, with the Lotus Sutra at the apex. Tendai ended up so comprehensive – across ritual, contemplation, faith and morality – that Saichō saw no need for any other sect in Japan.

Saichō dubbed his teachings ‘Buddhahood for all’. The basic idea was very much in tune with the Mahayana branch of Buddhism. Coalescing in India by around 200 CE and mixing with Chinese philosophical and religious traditions across the centuries since, the Mahayana (‘Great Vehicle’) had helped to broaden Buddhism from being the preserve primarily of monastics to a ‘vehicle’ for the salvation of laypeople too. Devotional possibilities expanded with the idea that the Buddha takes on three different forms or ‘bodies’: a cosmic, all-embracing form, akin to the Absolute; a celestial form, appearing as various gods inhabiting the realms that make up the cosmos; and more limited forms manifesting in ordinary time and space – the most famous being Siddhartha Gautama. There was great emphasis, too, on the figure of the ‘bodhisattva’: beings on the path to Buddhahood across many lives, who out of compassion seek to release all other sentient beings from suffering along the way.

For Saichō, ‘Buddhahood for all’ meant that traditional distinctions between clergy and laypeople, and between men and women, did not matter. What mattered was that the Buddha in his cosmic form resided in the depths of every person, as their ‘Buddha nature’. Enlightenment was, as a result, not something to be striven for across many lifetimes via monastic vows, complex rituals and unending austerity. It was already here, already the truth of things, needing only to be apprehended via a simple faith nourished in contemplation and everyday life – if, that is, a person really wanted it. As Saichō himself cautioned his followers: ‘There is room for food and clothing within an aspiration for enlightenment, but there is no room for an aspiration for enlightenment within the quest for food and clothing.’

In one respect, Saichō was developing here a characteristically East Asian take on Buddhism. In India, the idea of reincarnation was so deeply entrenched that moral effort across many lifetimes seemed an entirely natural proposition. In China and Japan, by contrast, where reincarnation was just one amongst many possible posthumous outcomes, Buddhism came to have a greater focus on the here-and-now; on the possibility that people, even inanimate objects, possess the Buddha nature; and on the religious practices and artistic ways of looking at the world that flow from that.

But the politics of Tendai were distinctive and clear from the start. Saichō regarded Prince Shōtoku as a great statesman and his ‘spiritual grandfather’. Where the Prince was credited with helping to establish ‘Nihon’ as his country’s name, Saichō was amongst those to use the powerful expression dainipponkoku: ‘the great country of Japan’. The cosmic protection of this great country, he claimed, and its freedom from chaos, was one of Japanese Buddhism’s most weighty responsibilities.

If Saichō was Kanmu’s ideal Buddhist – scholarly, moral, highly patriotic – he nevertheless had a rival in a second Buddhist monk arriving in China in 804 as part of the same diplomatic mission. His name was Kūkai, and just like Saichō he returned to Japan to establish a brand new Buddhist sect. Where Tendai was broad in its philosophy and ritual, Kūkai’s new sect – Shingon (‘True Word’), which came to be based on Mount Kōya – focused more closely on esoteric Buddhism. Monks studied mudras (ritual gestures, mostly using the hands), mandalas (visual representations of sacred realms), mantras (sacred phrases) and mental concentration.

Saichō and Kūkai became two of the most influential Japanese Buddhists who ever lived. Their rise might not have been good news for women, who thrived as nuns in the existing system but were, early on at least, barred from Mounts Hiei and Kōya for fear of compromising the efficacy of the rituals performed there. But where Buddhism in Japan had, in the past, relied heavily on foreign scholarship, Saichō and Kūkai were its first great Japanese innovators.

Japan’s native gods, meanwhile, remained very much in the picture. At its own request, via an oracle, the kami Hachiman had been moved from Kyūshū to Nara, so that it could pay homage to the great Buddha at Tōdai-ji. Now, the Tendai and Shingon sects turned to the kami of Mounts Hiei and Kōya respectively to help secure themselves in their new homes. Buddhism and the kami would continue to interweave – philosophically and ritually – for a millennium to come, so that eventually few Japanese would recognize them as two separable traditions.

Emperor Kanmu did not live to see the full fruits of his boundary-pushing efforts, which contributed so much to Japan’s Heian era, beginning with the establishment of the new capital and ending in 1185. Already unwell by the time Saichō returned from China in 805, Kanmu died the following year, after an esoteric Buddhist ritual intended to revive him failed to achieve its end. But in the decades following his death, Buddhism’s boundaries were steadily and radically redrawn thanks to his support for Saichō and Kūkai: from an urban system in which six sects mixed and mingled, to a mountain tradition, firmly rooted in Mahayana Buddhism, where differing sects maintained their own temples, lineages, interests and eventually even armies.

More broadly, Kanmu had helped to usher in an era of remarkable cultural confidence in Japan. He left his country on the cusp of a classical era in which contacts with China fell away and instead fashion, art, architecture, music, poetry and prose all took on distinctively Japanese forms. Tendai and Shingon had an important part to play here. The idea that Buddha nature resides in everyone and everything made possible a shift from the relative austerity of the Nara schools to a broad and enthusiastic embrace of aesthetics as yet another means of accessing the Absolute. Kūkai became famous not just as a Buddhist pioneer but also as a poet, painter and calligrapher. For centuries to come, some of Japan’s greatest artists would also be Buddhist priests.

Kanmu’s new capital at Heian-kyō became synonymous with these celebrated cultural achievements. The city was also the governmental and administrative heart of a centralized imperial realm that encompassed most of the islands of Kyūshū and Shikoku, along with southern and central areas of Honshū. Its population stood at around 6 or 7 million people in Kanmu’s lifetime. Thanks to his political achievements and his siring of three strong sons – whose combined reigns continued until 833 – Kanmu’s legacy in all these areas was given time to develop before enemies crowded in.

But crowd in they would. Clan power had been dampened down, not defeated. Before too long, successors to the imperial throne would look back on Kanmu’s era less as a practical example and more as a glorious and utterly irretrievable past.