In the early months of 1467, two armies totalling somewhere north of a hundred thousand men faced each other across fortified barricades in the streets of Kyoto, the imperial capital of Japan, a city of temples and poetry and exquisitely cultivated aesthetic sensibility. The man who was nominally in charge of the country, the eighth Ashikaga shogun, Yoshimasa, had a clear view of the opening engagement from the windows of his residence. He chose to watch the battle the way he chose to handle most obligations of governance: passively, with a cup of tea, before returning to the business of planning his retirement villa.

The armies were led by his two most powerful vassals. They were fighting, ostensibly, over which of Yoshimasa’s relatives would inherit the title he could not be bothered to exercise. The war they started would last ten years, reduce Kyoto to a wasteland, and destroy the political system that had governed Japan for more than a century. Out of the ashes would emerge a hundred years of civil war, a new breed of warlord who answered to no authority but his own sword, and, eventually, improbably, the conditions that would bring the first Europeans to Japanese shores.

This is the story of how a country fell apart, and what grew in the rubble.

· · ·

Part I

The Emperor Who Reigned Over Nothing

To understand how Japan arrived at the catastrophe of the Ōnin War, you first need to understand the peculiar architecture of Japanese power, a system that, by the mid-fifteenth century, had become an elaborate fiction maintained by inertia and the absence of anyone brave enough to point out that the machinery had stopped working.

At the apex of the structure sat the Emperor, descended, according to unbroken tradition, from the Sun Goddess Amaterasu herself. His authority was sacred, cosmic, and entirely theoretical. The Emperor performed rituals. He consecrated seasons. He bestowed titles. He did not, in any meaningful sense, govern. The imperial family had not wielded real political power for centuries, eclipsed first by the Fujiwara regents, then by successive lines of military dictators. By the 1400s, the imperial court in Kyoto was so impoverished that enthronement ceremonies were sometimes delayed for years because no one could scrape together the funds to pay for them.

And yet the Emperor could not be replaced. This was the beautiful paradox at the heart of the system. Because the imperial dynasty’s authority derived from divine descent rather than conquest, no warlord, however many provinces he controlled, however many enemies he had decapitated, could simply seize the throne. The dynasty was the source code of political legitimacy. You could ignore the Emperor, impoverish him, build your headquarters next to his palace and run the country without consulting him, but you could not be him. Every military ruler in Japanese history, from the Kamakura shoguns to Tokugawa Ieyasu, understood this. They ruled through the Emperor, not in place of him.

The mechanism for this arrangement was the shogunate, the bakufu, literally “tent government”, a name that preserved the polite fiction that the military ruler was merely a field commander temporarily managing affairs on the Emperor’s behalf. The shogun held the formal title Sei-i-tai-shōgun, “Barbarian-subduing Great General”, which had originally referred to campaigns against the indigenous Emishi peoples of northern Japan but had long since become a hereditary office that meant, in practice, “the person who actually runs the country”.

The system worked tolerably well when the shogun was strong. When the shogun was not strong, the fiction collapsed, and the real power arrangements underneath, messy, violent, and held together by personal loyalty rather than institutional authority, rose to the surface.

· · ·

Part II

The Ashikaga Bet

The Ashikaga shogunate came into being in the 1330s, born from the wreckage of its predecessor. When the Kamakura bakufu collapsed in 1333, Emperor Go-Daigo seized the moment to attempt something that no emperor had managed in centuries: direct personal rule. The Kemmu Restoration, as it became known, lasted approximately three years before collapsing under the weight of Go-Daigo’s inability to satisfy the warrior class that had made his restoration possible. Ashikaga Takauji, the general who had helped overthrow Kamakura, turned against the Emperor, drove him from Kyoto, installed a rival imperial line, and established his own shogunate in 1336.

The new regime made a decision that would define, and ultimately doom, it. Unlike the Kamakura shoguns, who had governed from the eastern city of Kamakura, far from the distractions and intrigues of the imperial court, the Ashikaga set up their headquarters in the Muromachi district of Kyoto itself. They wanted proximity to the Emperor, whose ritual authority they needed to legitimise their rule. They got proximity to everything else as well: the court’s factions, its rivalries, its cultural gravity, and its talent for converting military men into aesthetes.

The structural problem was more fundamental. The Ashikaga lacked a dominant territorial base. The Kamakura shoguns had controlled the eastern provinces directly. The Tokugawa, two centuries later, would command roughly a quarter of Japan’s total agricultural output. The Ashikaga had comparatively little land of their own, which meant comparatively little independent revenue, which meant comparatively few troops they could call their own. The shogunate functioned less as an autocracy than as a coalition, the shogun as chairman of the board, presiding over a collection of powerful military houses whose cooperation was voluntary and whose patience was finite.

The third shogun, Ashikaga Yoshimitsu, made the coalition work through sheer force of personality and political cunning. He suppressed rival factions, absorbed the functions of the civilian government, reunified the two competing imperial courts, and, in a move of breathtaking pragmatism, accepted the title “King of Japan” from the Ming Emperor of China, subordinating himself to the Chinese tributary system in exchange for a monopoly on the extraordinarily lucrative trade. Under Yoshimitsu, the Ashikaga reached their zenith. The Muromachi period that bears the shogunate’s alternative name became an age of extraordinary cultural production: Noh theatre, ink-wash painting, the tea ceremony, the aesthetics of wabi-sabi, much of what the modern world recognises as “traditional Japanese culture” crystallised during these decades.

But Yoshimitsu was the exception, not the template. After his death in 1408, the coalition began to fray. By the 1440s, the shogunate’s ability to project power beyond Kyoto had withered. Provincial governors ignored orders. Revenue dried up. The institutional scaffolding remained in place, but the authority it represented was increasingly hollow.

All it needed was a spark.

· · ·

Part III

A War Over a Baby

The spark, when it came, was both predictable and absurd: a family argument about inheritance, escalated by ambitious in-laws, weaponised by feuding vassals, and ignored by the one man who might have defused it.

Ashikaga Yoshimasa became the eighth shogun in 1449 at the age of thirteen. He grew into a man of refined aesthetic taste, genuine artistic patronage, and absolutely no interest in governing. The political crises that accumulated during his tenure — famine, peasant uprisings, provincial rebellions — received the same treatment: delegation, followed by indifference, followed by retreat into poetry and garden design. Yoshimasa’s Silver Pavilion, the Ginkaku-ji, remains one of the most celebrated examples of Muromachi architecture. It is also a monument to a man who chose to build a retirement villa while his country burned.

The succession problem was straightforward in its origins and catastrophic in its consequences. Yoshimasa had no son. Weary of governing, he persuaded his younger brother, Yoshimi, to leave a Buddhist monastery and accept designation as his heir, with the understanding that Yoshimasa would abdicate and retire to his art collection. Then, in 1465, Yoshimasa’s wife, Hino Tomiko, a woman of ferocious political ambition and considerable financial acumen, gave birth to a son, Yoshihisa. Tomiko had no intention of watching her child passed over in favour of his uncle, and she had the connections to do something about it.

The succession dispute became the organising principle for a confrontation that had been building for decades. Two immensely powerful provincial governor clans, the Hosokawa and the Yamana, had been circling each other like rival predators, and the question of the shogunal heir gave each a cause around which to mobilise. Hosokawa Katsumoto backed Yoshimi. Yamana Sōzen, a man whose nickname, the “Red Monk”, derived from his ruddy complexion and his brief, unconvincing stint as a Buddhist cleric, backed the infant Yoshihisa and, by extension, Hino Tomiko. Similar succession disputes within the Hatakeyama and Shiba governor houses added further fault lines. By 1467, the capital was an armed camp, and the polite pretences that had held the Ashikaga coalition together for a century were about to be incinerated, in some cases literally.

· · ·

Part IV

Ten Years of Ashes

The Ōnin War began with a skirmish in January 1467, when two rival claimants to the Hatakeyama governorship fought a pitched battle near the Goryō shrine in Kyoto while Shogun Yoshimasa watched from a nearby residence and did nothing. Within months, the Hosokawa and Yamana coalitions had fortified opposing positions within the city itself, with armies numbering in the tens of thousands digging in for what became a decade of grinding, inconclusive urban warfare.

The destruction was staggering. Kyoto had been the cultural heart of Japan for seven centuries, a city of temples, libraries, aristocratic mansions, and artistic treasures accumulated over generations. The armies burned it methodically, neighbourhood by neighbourhood. The great Shōkoku-ji monastery was destroyed. Aristocratic residences that had housed centuries of poetry collections and painted screens went up in smoke. The imperial palace was damaged. Civilians fled or died. The city that had produced the Tale of Genji and the aesthetics of courtly refinement was reduced to a landscape of charred timber and defensive trenches.

Yoshimasa, with consistency, continued to focus on tea ceremonies. He commissioned ink paintings. He planned the Silver Pavilion. The war raging outside his walls was someone else’s problem.

Both of the original antagonists, Hosokawa Katsumoto and Yamana Sōzen, died in 1473, within months of each other, the former of illness and the latter of what may have been a stroke. Their deaths resolved nothing. The war had long since outgrown the succession dispute that had triggered it, becoming a self-sustaining cycle of factional violence. Provincial lords who had brought their armies to Kyoto to support one side or the other found that returning home was impossible, or, worse, that returning home meant confronting the chaos that had erupted in their absence.

When the fighting finally sputtered out around 1477, it was not because anyone had won. The armies simply dispersed, broken by exhaustion and the growing realisation that the real prizes were no longer in Kyoto. The capital was a ruin. The shogunate was a shadow. And across the provinces of Japan, a new and terrifying political reality was taking shape.

· · ·

Part V

The World Turned Upside Down

The Japanese had a word for what happened next: gekokujō, “the lower overthrowing the upper”. It became the defining principle of the Sengoku period, and it was applied with a thoroughness that left no level of the old hierarchy intact.

The mechanism was brutally simple. The provincial governors, the shugo daimyō, who had spent years fighting in Kyoto returned to their home provinces to find that the men they had left in charge had decided they rather liked being in charge. Deputies had become lords. Stewards had become warlords. The chain of command that ran from shogun to governor to local warrior had snapped, and at every break point, the man below had seized the position of the man above.

The Asakura clan of Echizen, former deputies to the Shiba governors, overthrew their masters and ruled the province independently. In the Kantō region, a branch of the Ise family, later known as the Hōjō, rose from obscurity to dominate the entire eastern plain. The Nagao family of Echigo produced a retainer named Nagao Kagetora who overthrew the Uesugi governors so thoroughly that he adopted their surname and became, in the next generation, the legendary Uesugi Kenshin, “God of War”. And in the province of Kaga, the phenomenon reached its most radical expression: an army of peasants, local warriors, and monks affiliated with the True Pure Land Buddhist sect, the Ikkō-ikki, overthrew the provincial governor and ruled the entire domain as a religious commune for nearly a century.

Traditional rank ceased to matter. Lineage ceased to matter. Shogunal appointments, imperial patents, ancestral pedigrees, none of these offered any protection against a vassal with more soldiers and fewer scruples. The Sengoku period, which historians conventionally date from the outbreak of the Ōnin War in 1467 to the late sixteenth century, was an era in which political legitimacy flowed from one source only: the ability to hold territory by force.

· · ·

Part VI

The New Warlords

The men who thrived in this environment were a fundamentally different breed from their predecessors. The old shugo daimyō had derived their authority from the shogunate, governing provinces by appointment and drawing their legitimacy from the Ashikaga seal. The new Sengoku daimyō derived their authority from themselves. They built castles, recruited armies, issued their own legal codes, the bunkokuhō, “provincial laws”, and administered justice, collected taxes, and managed commerce without reference to any higher authority, because no higher authority existed.

Their domains were compact, contiguous, and ruthlessly efficient. Takeda Shingen of Kai Province, famous for his cavalry tactics and his decades-long rivalry with Uesugi Kenshin, turned his landlocked mountain domain into a military machine of extraordinary discipline. The Mōri clan of western Honshū rose from minor provincial warriors to control ten provinces through a combination of strategic marriages, well-timed betrayals, and the occasional assassination. In the east, the Hōjō built a domain centred on Odawara that functioned as a proto-state, with standardised taxation, cadastral surveys, and a bureaucracy that would have impressed, and alarmed, the administrative class in Kyoto.

The castle towns, jōkamachi, that these warlords constructed around their fortresses became the nuclei of a new urban geography. Merchants and artisans were drawn to the security and commerce that surrounded a powerful lord’s stronghold. Markets grew. Trade routes shifted. A generation of castle towns that had begun as military encampments evolved into the commercial cities that would define early modern Japan.

The irony of the Sengoku period is that the violence produced dynamism. Agricultural productivity increased as competing daimyō invested in irrigation, land reclamation, and anything else that might expand their tax base. Domestic trade flourished along the new routes that connected castle towns. International commerce, conducted through the ports of northern Kyushu, where Japanese merchants traded with Chinese, Korean, and Southeast Asian counterparts, brought silver, silk, and ideas into a country that was simultaneously tearing itself to pieces.

It was into this landscape of ambition, innovation, and relentless warfare that Portuguese adventurers stumbled ashore on Tanegashima in 1543, carrying with them a technology that every daimyō in the country would immediately recognise as the most important thing they had ever seen: the gun.

· · ·

Sources & Further Reading

Berry, Mary Elizabeth. The Culture of Civil War in Kyoto. Berkeley: University of California Press, 1994. The definitive study of Kyoto during the Ōnin War and its aftermath, examining how the capital’s cultural and political institutions adapted to, and were transformed by, a decade of urban warfare.

Varley, Paul. The Ōnin War: History of Its Origins and Background with a Selective Translation of the Chronicle of Ōnin. New York: Columbia University Press, 1967. The standard English-language treatment of the war that triggered the Sengoku period, including translations of primary source material.

Elison, George, and Bardwell L. Smith (eds.). Warlords, Artists, and Commoners: Japan in the Sixteenth Century. Honolulu: University of Hawai’i Press, 1981. An invaluable collection of essays covering the political, cultural, and social dimensions of the Sengoku period.

Lamers, Jeroen P. Japonius Tyrannus: The Japanese Warlord Oda Nobunaga Reconsidered. Leiden: Hotei Publishing, 2000. A critical reassessment of Nobunaga that challenges the mythology surrounding his military innovations and political vision, drawing extensively on Japanese primary sources.

Hall, John Whitney, Nagahara Keiji, and Kozo Yamamura (eds.). Japan Before Tokugawa: Political Consolidation and Economic Growth, 1500–1650. Princeton: Princeton University Press, 1981. Essential scholarly collection covering the economic and institutional transformations that accompanied the Sengoku-to-Tokugawa transition.

Fróis, Luís, S.J. Historia de Japam (5 vols.), ed. José Wicki. Lisbon: Biblioteca Nacional de Lisboa, 1976–1984. The monumental Jesuit chronicle that provides the most detailed European eyewitness accounts of Nobunaga’s career, the Sengoku political landscape, and the early Portuguese-Japanese encounter.

Cooper, Michael, S.J. (ed.). They Came to Japan: An Anthology of European Reports on Japan, 1543–1640. Ann Arbor: University of Michigan Center for Japanese Studies, 1995. Curated translations of Portuguese, Spanish, and other European accounts, including Fróis’s descriptions of Nobunaga and the political environment of sixteenth-century Japan.

Turnbull, Stephen. The Samurai Sourcebook. London: Cassell, 1998. A comprehensive reference covering Sengoku-era military organisation, major battles (including Okehazama and Nagashino), and the social structure of the warrior class.

Boxer, C.R. The Christian Century in Japan, 1549–1650. Manchester: Carcanet Press, 1951. The foundational English-language study of the Portuguese-Japanese encounter, providing essential context for understanding how the Sengoku political environment shaped the conditions for European contact.

Souyri, Pierre-François. The World Turned Upside Down: Medieval Japanese Society, trans. Käthe Roth. New York: Columbia University Press, 2001. A social history of medieval Japan that illuminates the gekokujō phenomenon and the fluid class boundaries that characterised the Sengoku period.

Adolphson, Mikael S. The Gates of Power: Monks, Courtiers, and Warriors in Premodern Japan. Honolulu: University of Hawai’i Press, 2000. Important for understanding the political role of Buddhist institutions in the pre-Sengoku and Sengoku periods, and the context for Nobunaga’s campaigns against monastic power.