Dark Ages, is known in Japanese climatology circles as the Kofun Cold Stage, a dip in temperatures substantially worse than that known in Europe as the “Little Ice Age.” Global temperatures fell, with a mysterious “dry fog” recorded in both China and Europe that reduced the impact of solar radiation for over a decade in the mid-sixth century and led to widespread famines and outbreaks of disease. Japanese weather, too, turned colder and wetter; several archaeological sites have been preserved because they were abandoned after floods.
This period dealt substantial damage to the surviving indigenous peoples of Japan, but allowed the more technically advanced immigrant communities to flourish. By 200 CE, the arrival of iron had brought swift changes to the Japanese realm. The locals continued to build with timber, but were able to access far more of it with the new efficiency of metal tools. Just as modern Japanese cutlery reflects a scarcity of metal—knives and metal implements are used in the kitchen, but not at the table—most of the Yayoi people continued to work with wooden tools, attesting to the rarity of early iron objects. However, many of these wooden tools themselves, such as shovels and rakes, became more widespread and efficient because of the availability of iron tools to make improved versions. Architecture, too, became straighter, as fences and beams were hewn with truer blades. Land was swiftly cleared, and the primeval forests were decimated in the quest for materials, but this also allowed for the development of agriculture on a larger scale.
The trees stayed on the mountainsides, where they kept the soil in place and allowed for reliable amounts of water flowing down the slopes into the new rice paddies. Japan’s volcanic soil was relatively poor for agriculture, but could be tricked into producing higher yields by flooding the fields. Communities that could grow their own food could forge ahead, as could those that stored surplus produce “for evil years.”
The Ise Shrine, one of the most sacred sites in Japan, is particularly useful for understanding the ancient country. Ever since the shrine was first rededicated by Empress Jitō around 692 CE, it has existed in two forms: the “original” wooden thatch-roofed building, and a copy under construction alongside. The shrine is rebuilt as an exact copy of itself every twenty years, echoing a similar narrative of demolition and renewal that seemed to accompany changes in omens or dynasties among the Japanese of the distant past. It also gives us a clue as to the architecture of ancient Japan—sturdy constructions of cypress wood above a ground of white pebbles and around a sacred central pole, with extended finials that give each roof a crossed, horned profile. It is possible that many of the buildings of the ancient Japanese capital looked like these before developments in technology and materials dragged them away from the original plans.
The Kofun period, however, takes its name from a different kind of architecture, the massive “ancient graves” (kofun) that dot the Japanese landscape. The simple, square burial mounds of the Yayoi period give way during the third century CE to huge tumuli featuring a distinctive combination of a rounded top connected to a trapezoid mound. From above, this makes them appear to be shaped like keyholes, and indeed they are often referred to as “keyhole tombs.” Their oldest examples date from the Nara area, but in the ensuing centuries they proliferated elsewhere, implying a dominant aristocracy that took its manpower and customs further and wider.
The contents of the kofun would surely have much to tell us about this period in Japanese history, but their sacred status as the resting places of ancient Japanese “emperors” keeps them largely off limits to archaeological exploration. There are, tantalizingly, several similar keyhole-shaped tumuli to be found in Korea, in the Yeong-san river basin in what was once the state of Baekje, implying strong cultural connections between the builders of both.
Although Japan was already occupied from end to end, the narrative in the Yayoi period takes on a new tone. The story of what would become Japan is not now told by the Jōmon peoples, and possibly not even by their most impressive inheritors, the Yamatai. Instead, it becomes a story told by people whose arrival from the mainland is indicated by in the form of a large mound burial in the first century BCE in Kyūshū, the island closest to Korea, and a gold seal from around the same time found in the Fukuoka region.
Chinese chronicles report “disturbances in Wa” around the middle of the second century CE as these new arrivals, armed with iron that cut down both enemies and forests, began to push ever further up the coast. The corpses in their Japanese graves are notably taller than the locals, perhaps explaining why dispatches back to the mainland referred to a land of “dwarves” in the first place. There is a palpable break in the line of Japanese kings around the late fourth century, possibly related directly to unrest on the mainland that saw the collapse of the Kara state, with up to a million refugees arriving in Japan. These migrants, however, appeared to be arriving with their wealth intact, and were soon interfering with and influencing the politics and power struggles of local kingdoms. Some of the indigenous Jōmon people fled north to escape the newcomers, while others seemed to welcome them, even as they were swamped by their numbers. The archaeological record reveals a double impact—first of a huge influx of these new bloodlines, forming 73 percent of the population in some areas—and then of the inevitable increase of the newcomers’ numbers as they bred both among themselves and with the locals.
Where Chinese chronicles once described everyone on the islands as “barbarians,” now there is a new narrative of civilization in the hands of these fresh arrivals, pushing back against the barbarians of the periphery. For centuries thereafter, there would be a frontier in the north—a place where young men might carve out a career on the marchland; where “barbarians” on the edges were divided into the good ones who had assimilated and the bad ones who pushed back. The long march northward would only come to an end in the nineteenth century, when the Japanese staked their claim on the last stretch of wilderness in the far northern island of Hokkaidō. There, the local Ainu people bore an unsurprising resemblance to the original inhabitants of Japan in many of the accounts from the ancient past, now eking out an existence on the very edge of the land that was once theirs.
By the early third century, the keyhole tombs had made it as far as the Kansai plain—the heartland of Queen Himiko’s legendary kingdom. Notably, they contain very few shell bracelets; the old ruling class had been supplanted. Mainland technology and genes soon wormed their way into the local elites. Deforestation rapidly escalated as these newcomers pursued new housing, new land cleared for crops, and new social projects such as dams and dikes.
It is likely that the confused historical record obscures a dual struggle for influence, as the old kingdoms jostled for power and the newcomer elites fought for recognition not only in the community of local kingdoms, but also back on the mainland, where they intervened in Korean politics.
Owing to the muddled condition of Japanese annals, the real dates are impossible to determine. Chroniclers, like readers, are apt to be confused by repetitive accounts of wars across the straits and kings begetting heirs, and are frustrated even further when a quick count soon establishes that these sovereigns appear to have superhuman lifespans, coming to the throne in adulthood and still somehow managing to rule for over a century. Your guess is as good as mine as to how historical a figure the dragon-slayer Yamato Takeru was—probably not all that much, although his son Chūai is another generation closer to the time when the annals were set down. It was the biographers of Chūai’s widow, Jingū, however, who really muddied the waters. The Kojiki reports her setting sail for Silla on the Korean peninsula with an invasion fleet, which speeds across the strait, borne on the backs of helpful fishes and a generous tailwind. The ruler of Silla, seeing this unlikely entourage approaching, does not even bother to fight, but swears allegiance to Jingū, pledging himself as a mere stable-boy to the sovereign of “Heaven,” and vowing that “each and every year, for as long as heaven and earth remain” he will send ship after ship in a constant rotation of tribute, specifically in horses.
The whole story is foggy with poetic license, and so wracked with portents and sorcery, along with strange turnabouts of fate, that one might just as easily interpret it as an account of a Korean invasion of Japan, but it does seem to bear a much closer resemblance to Japanese attitudes substantially later than the chapters in the Kojiki. Move the stories of tribute and alliance later—to, say, 369 CE—and they suddenly bear a much closer resemblance to cross-straits actions reported in Korean annals,