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29th day of the 11th month, Tenshō 13 (January 18, 1586)
Hida, Etchu, Ōmi, and Mino provinces (epicenter: Hida Mountains region)
About 19 min read
The Tenshō Great Earthquake (Tenshō daijishin) was the largest-scale seismic disaster of the late Sengoku period, occurring in the deep of night on November 29 of the 13th year of Tenshō (January 18, 1586 in the Western calendar). The epicenter is estimated to have been in the Hida Mountains spanning present-day Gifu, Toyama, and Nagano prefectures, with magnitude estimated between 7.8 and 8.1. The shaking extended across a vast region encompassing Hokuriku, Tōkai, and the Home provinces, causing catastrophic damage to castles, temples and shrines, and private homes throughout. This earthquake occurred the same year that Toyotomi Hideyoshi assumed the position of kampaku (regent), making it a major disaster at the most politically crucial moment—the eve of the unification of Japan—and it has drawn attention from historical, cultural, and sword-historical perspectives.
While records of damage preserved in historical sources are fragmentary, their severity is evident in references scattered throughout ancient records, shrine and temple histories, and letters of various daimyo. In Hida Province (present-day Takayama area, Gifu Prefecture), mountain collapses occurred frequently and settlements were buried. In the basins of the Shōgawa and Jinzu rivers, landslides dammed the waterways, and it is said the course of the rivers changed. In Etchu Province (present-day Toyama Prefecture), building collapses and fires ensued one after another; the domain of Sasaki Shigenari, who ruled Etchu at the time, suffered tremendous losses.
In Ōmi Province (present-day Shiga Prefecture), the Nagahama Castle of Yamanouchi Kazutoyo, who controlled northern Ōmi at that time, had its tenshu damaged, and it is said Kazutoyo's daughter was crushed to death. Furthermore, damage was also reported in Mino Province (present-day Gifu Prefecture). The estimated death toll is said by some accounts to have reached several thousand to over ten thousand, making it the largest-scale natural disaster of the Sengoku era.
Particularly noteworthy is that this earthquake occurred in the year after the Battle of Komaki-Nagakute of the 12th year of Tenshō (1584) and when Toyotomi Hideyoshi assumed the position of kampaku in the 13th year of Tenshō (1585). There is a historical irony: as Hideyoshi's power reached its apex, the trembling earth shook the very foundations of his unification.
The impact the Tenshō Great Earthquake exerted on Japanese blade culture can be examined from both direct and indirect perspectives.
As the most important direct impact, the scattering and loss of precious and famous blades housed in castle treasuries and temple and shrine repositories due to earthquake, fire, and chaos was significant. Medieval blades were frequently enshrined in castle treasuries and temple treasure halls; countless blades likely vanished when these buildings collapsed. Many blades in the possession of Hida and Etchu military commanders, passed down through generations, may well have been lost amid the post-earthquake chaos. One of the primary causes of breaks in Japanese blade "transmission" is precisely such loss due to natural disaster, warfare, and fire, and the Tenshō Great Earthquake stands as a symbolic instance of this in blade history, quietly acknowledged if not always explicitly noted.
As an indirect impact, the large-scale damage from the earthquake affected the domain governance and military operations of various daimyo. Daimyo who suffered damage were forced to prioritize reconstruction of their territories, which shifted political and military developments. In the conflict between Sasaki Shigenari and Hideyoshi over Etchu, the post-earthquake chaos formed one of the complex circumstances.
At the time of the Tenshō Great Earthquake, Maeda Toshiie ruled Noto, Kaga, and Etchu provinces and held significant standing within the Toyotomi regime. The Maeda clan had long placed importance on blades and was diligent in the acquisition and preservation of famous swords. The Daitentō Mitsuyo (National Treasure, currently held by the Maeda Ikutokukai Collection), passed down through the Maeda family, is counted among the "Five Greatest Swords Under Heaven." This tachi, attributed to Miike Tentō Mitsuyo, a celebrated swordsmith from the late Heian period, was preserved in the Maeda family's hands even after the Tenshō Great Earthquake. This blade is known for its wild hamon and large proportions, and it endured as a family treasure embodying the Maeda clan's authority through numerous conflicts and natural calamities.
Toyotomi Hideyoshi himself actively collected famous blades during this period, and his collection was enriched by swords presented in tribute or granted as gifts from the imperial court and daimyo. Following the Tenshō Great Earthquake, Hideyoshi provided aid to the stricken daimyo, further strengthening his political dominance. Blades were political symbols; the gifting and presentation of famous swords was evidence of submission. The image of a daimyo, whose domain had been devastated by the earthquake, presenting a famous blade to Hideyoshi came to symbolize the political character of swords in the late Sengoku period and attracted the attention of later scholars.
While the Tenshō Great Earthquake was purely a natural phenomenon, its political repercussions cannot be ignored. Sasaki Shigenari of Etchu had surrendered to Hideyoshi in August of the preceding year, the 13th year of Tenshō (1585), and this great earthquake struck his territory in the following November of the same year. By skillfully leveraging the earthquake's chaos to support and control the affected regions, Hideyoshi further accelerated the consolidation of his authority toward the unification of Japan. In that same year, the pacification of Shikoku and Kyushu also progressed, bringing Hideyoshi's hegemonic enterprise near completion.
In the history of Japanese swords, natural disasters such as earthquakes, fires, and floods have been primary causes of the dispersal of famous blades. The Tenshō Great Earthquake was no exception; records of lost famous blades and scattered swords survived in only fragmentary form in later generations. This earthquake, remembered as an "invisible rupture," became inscribed at the intersection of Japanese blade history and Japanese history as a fact: the earth on which the blades of the Sengoku era were forged trembled.
The Hida and Etchu regions, near the epicenter of the Tenshō Great Earthquake, were also areas where independent swordsmiths worked during the medieval period. Swordsmiths of Hida are confirmed to have existed from the Heian and Kamakura periods, while Etchu produced renowned masters of the Sōshū tradition, represented by Norishige of Etchu. Norishige's blades are known for their distinctive itame-hada (wood-grain steel), and are inscribed in blade history as one of the pinnacles of the Sōshū school alongside Masamune and Sadamune. However, due to the earthquake and warfare, the swordsmith culture of this region gradually declined, and by the later Edo period, Mino, Bizen, and Yamashiro emerged as the centers of sword production.
The Tenshō Great Earthquake likely caused direct damage to the workshops, tools, and lives of swordsmiths in Hida and Etchu. Sword-forging is a dangerous craft utilizing high-temperature furnaces, large anvils, and heavy hammers; collapse of furnaces, fire, and loss of tools were inevitable in such a seismic event. Medieval swordsmith workshops consisted primarily of wooden structures without modern earthquake-resistant design and were extremely vulnerable to strong tremors. Records of lost smithing tools and techniques never reached later generations, and one cannot deny the aspect that the earthquake accelerated the "rupture" in blade culture.
Fascinatingly, Toyotomi Hideyoshi was struck by another major earthquake nine years after the Tenshō Great Earthquake. The Fushimi Earthquake of Keicho 1 (1596), with an estimated magnitude of 7.0–7.5, caused substantial damage to the stone walls and structures of Fushimi Castle, which Hideyoshi was constructing as his residence. Several hundred are said to have perished in the collapse of Fushimi Castle, and while Hideyoshi himself escaped harm, he was profoundly shaken. This Fushimi Earthquake occurred on the eve of the Imjin War (1597–1598) and came to be remembered as an event symbolizing the misfortune of Hideyoshi's declining years. During Hideyoshi's lifetime, two great earthquakes—the Tenshō Great Earthquake (1585) and the Fushimi Earthquake (1596)—shook Japanese history, each leaving indelible marks on blade culture and transmission. The Tenshō Great Earthquake announced the dawn of the Toyotomi regime, while the Fushimi Earthquake heralded its twilight, both embodying in the earth's tremors the fateful bond between "blades and earthquakes" in Japanese history.
The Tenshō Great Earthquake holds significant historical-documentary value in modern seismic research as a major pre-modern earthquake. From the perspective of historical seismology, this earthquake may have resulted from a complex type involving activity across multiple plate boundaries, and research continues as an important case study for deepening our understanding of Japan's seismic belts. Furthermore, from a cultural heritage preservation standpoint, the losses of historical and cultural legacies—castles, temples and shrines, and transmitted treasures—wrought by natural disasters like the Tenshō Great Earthquake are incalculable. As a historical lesson reaffirming the critical importance of disaster preparedness and earthquake resistance for modern cultural property protection, the memory of this earthquake should be preserved and learned from. Blades are no exception. Recent examples exist of National Treasures and Important Cultural Properties designated as Japanese swords sustaining damage when museums and art galleries housing them experienced earthquakes, and over 430 years after the Tenshō Great Earthquake, the difficulty and significance of protecting famous blades remain unchanged. The very history through which the blades of the Sengoku era have endured speaks to the significance of cultural heritage preservation.