Who Were the Mononobe and the Soga? What Was Lost When Rulers Changed

The conflict between the Soga and the Mononobe, however, was not only a difference in religious outlook. Seen from another angle, it was a struggle for political power in Yamato (the southern part of Nara Prefecture), fought by making use of continental culture, chiefly Chinese.

We should note, in other words, that the contest between the pro-Buddhist Soga and the anti-Buddhist Mononobe was driven far more by practical gain than by religious conviction.

The Mononobe resisted vehemently, arguing that worshipping a foreign religion would provoke the wrath of the native kami.

The age reads best as a symbolic clash between the "native gods" and a "new god (the Buddha) from abroad," and as a power struggle played out on a stage of plague and fire.

The true origins of the Soga remain shadowy, but southern Nara was then home to many people who had come from across the sea—from the Asian mainland and the Korean peninsula. Given that the Soga rose to power on the strength of these networks, I suspect they themselves were deeply intertwined with continental lineages.

Behind the Soga's promotion of Buddhism stood many immigrant engineers and groups of naturalized people, and we must not overlook that. It is not that the Japanese of the time had a strong faith and so Buddhism began in Japan.

The Yamato no Aya, who served the court, are one example. The name covers several clans that came from China and Korea, and they held advanced skills in ironworking, saddlery, and civil engineering.

Another theory deserves mention: that the Soga embraced Buddhism because they were themselves of immigrant origin.

The Soga's origin remains unclear, but in the course of my own research in Nara I have seen one possibility.

When the Soga fell, they burned most of the documents of their origin, so nothing can be said with certainty even now.

Up to that point, the balance of power at court had rested on three great pillars of the native ritual order — the Mononobe, the Nakatomi, and the Otomo — who held overwhelming authority and guided the sovereign.

Standard accounts still tell us that the Mononobe were annihilated. Yet "annihilation" is a misleading word; the entire lineage did not simply perish on the battlefield.

Yet the Mononobe were not merely ritual specialists overseeing imperial rites; they were hereditary masters of court military power, and the fighting was extraordinarily fierce.

The Mononobe, struck down by the Soga, are said in history to have perished, but some survivors may have branched off from the Mononobe and stayed on around the court. They had lost political power in the court, and those in the main line were executed, but not everyone died, and the line was not broken. In fact, when the Soga hegemony had ended and the fortieth emperor, Tenmu (r. 673–686), was building a new age by one reform after another, a person with what seems to be the surname Ato is recorded.

Remarkably, memories of this prehistoric realm survive in the topography and folk belief of the region: just beyond Mount Ikoma on the Nara side lies the district of Tomi. Preserved in modern place names like Tomio (富雄) and Tomigaoka (登美ヶ丘)—likely remnants meaning "heroes of Tomi" and "the hills of Tomi"—the landscape still carries the imprint of that antiquity.

And myth tells us something more: Nagasunehiko was already subordinate to a higher divine power. That god was none other than Nigihayahi—the mysterious sovereign deity of Yamato, and the divine ancestor of the Mononobe clan.

Compounded by the remarkable longevity of the Soga chieftain Soga no Umako (551–626), what followed was a virtual dictatorship in which Umako held the reins of the court for fifty-four years — a span during which Buddhism, needless to say, spread with extraordinary speed.

Umako wielded power that eclipsed that of the sovereign himself; when the thirty-second ruler, Emperor Sushun (r. 587–592), chafed at Umako's dominance, Umako promptly had him assassinated — the only confirmed assassination of a reigning emperor in Japanese history — giving those around him ample reason for grievance.

Two principal figures met at Tanzan Shrine. The first was Prince Naka no Oe (626–672), a prince of the imperial blood who would later ascend the throne as Emperor Tenji. The second was Nakatomi no Kamatari (614–669), a scion of the Nakatomi clan.

Yet Buddhism had spread so rapidly across the land under Soga rule, leaving behind a network of temples and statuary, that the victors could hardly escape its gravity.

Emperor Tenji viewed the fall of his primary ally as an existential peril: should Tang and Silla conquer the entire peninsula, the archipelago would surely be their next target. He resolved to dispatch a massive expeditionary force to restore Baekje.

In 663, at the mouth of the Geum River in what is now South Korea, the allied fleet of Japan and Baekje met the joint forces of Tang and Silla in the Battle of Hakusukinoe (Baekgang).

The defeat at Hakusukinoe sparked transformations comparable in magnitude to Japan’s passage from the Edo period through the Meiji Restoration into the modern era.

Having hemorrhaged authority, the court accelerated the adoption of the ritsuryo legal framework, hastening the transition toward a centralized bureaucratic regime under imperial rule.

Japan abandoned direct confrontation in favor of tributary diplomacy, dispatching kentoshi (遣唐使) embassies to the Tang court, ushering in an era when Buddhism flourished across the islands.

To dismantle that oligarchy and rule directly, Tenmu faced a formidable obstacle: the divergent genealogies and myths preserved by the noble clans. These oral traditions legitimized each clan's independent roots; unless those ancestral claims were subordinated to and woven into the imperial lineage, the clans saw no compelling reason to obey the throne. So long as that archaic autonomy persisted, genuine centralized governance was impossible, leaving Japan helpless against the threat of Tang China. Grasping this peril, Tenmu resolved to subordinate all ancestral roots under imperial oversight. It was this imperative that launched the compilation of Kojiki as the realm's first sweeping ideological state project.

Because Japan had gone without writing since ancient times, there were no books concerning ancient Japan, and even after a culture of writing and books arrived by way of China around the time Buddhism was introduced, earlier texts were lost or vanished into the dark amid turmoil as rulers changed in rapid succession.

Bear in mind, however, that rather than equating this directly with the history of Japan as a whole, we should see it as the history of an exceedingly limited region. In Japan too there is a common tendency to treat this as synonymous with Japanese history, yet it is simply an account of the map of power on the southern side of the Nara Basin known as Yamato, and is confined to certain forces in western Japan with whom they traded, formed alliances, or brought into submission.

Indeed, the western side in the opposite direction was held by the Katsuragi clan, another ancient clan with deep roots, and the southern side may well have been held by yet another clan. In this way, I feel that the true image of what we call ancient Japanese history has been used down to the present day under an exceedingly vague definition.

When we look at the movements of the Soga clan, who expanded their power around the time Buddhism arrived, they rose from the southern side of the Yamato Basin in present-day Asuka, Nara Prefecture, which leads me to think that at least as of the sixth century, Yamato was still in a state of rival chiefs contending for supremacy.

In truth, the founding origins of such shrines can rarely be established with certainty, yet at the very least, the area around here holds the roots from which the Mononobe tribal group arose. And even before Kamuyamato Iwarebiko (神倭伊波礼比古命) set out on his eastern expedition from Hyuga (the coastal region of present-day Miyazaki Prefecture), seized hegemony over Yamato, and ascended the throne as the first emperor, Emperor Jimmu, on the grounds of Kashihara Shrine in present-day Kashihara, Nara Prefecture, the Mononobe clan already held the authority that governed this region.

Even so, it is plainly recorded that the Mononobe clan handed down from generation to generation not the "Three Sacred Treasures" (Sanshu no Jingi, 三種の神器) inherited by successive emperors as the proof of the throne, but a set of treasures known as the "Ten Sacred Treasures" (Tokusa no Kandakara, 十種神宝).

The Sendai Kuji Hongi contains many fascinating passages, yet because the Mononobe clan in a later age submitted to the group around Kamuyamato Iwarebiko of the Hyuga line (the imperial line), the text underwent external alterations in service of venerating the emperor, making it an exceedingly difficult task to discern where its ancient strata lie.