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29th day of the 11th month, Tenshō 13 (January 18, 1586)
Hida, Etchū, Ōmi, Mino, Owari, Ise, and others (the source fault is disputed)
About 17 min read
The Tenshō earthquake (Tenshō Ōjishin) was the largest earthquake disaster of the late Sengoku period. It struck on the night of the 29th day of the 11th month of Tenshō 13 (January 18, 1586), at the hour of the Boar (around 10 p.m.). There is no established theory about its epicenter. There are theories that multiple faults moved, including the Shōgawa fault zone and Atera fault zone in Hida, and the Yōrō–Kuwana–Yokkaichi fault zone in Mino and Ise. Its magnitude is estimated at around 7.8 to 8.2. The shaking extended across a wide area of Hokuriku, Tōkai and Kinai, and caused severe damage to castles, temples, shrines and ordinary homes. This earthquake occurred in the same year Hideyoshi took the post of kampaku. As a great disaster during the period just before the unification of the realm, the most politically important time, it has drawn attention from the perspectives of history, culture and swords.
Historical records of damage survive only in fragments, but descriptions showing its severity appear scattered across old chronicles, temple and shrine histories, and the letters of various daimyo. In Hida Province (present-day northern Gifu Prefecture), Mount Kaerikumo collapsed, burying Kaerikumo Castle and the surrounding settlements, and its lord Uchigashima Ujitoshi and his family were reported missing. In the upper reaches of the Shō River, landslides dammed the river and formed a natural dam, which later broke and caused damage in the river basin. In Etchū Province (present-day Toyama Prefecture), Kifune Castle collapsed, and its lord Maeda Hidetsugu (younger brother of Maeda Toshiie) and his wife and others died.
In Ōmi Province (present-day Shiga Prefecture), Nagahama Castle, which Yamauchi Kazutoyo used as his residence, was completely destroyed, and it is said that Kazutoyo's only daughter, Princess Yone (Yone-hime), was crushed to death. Damage was also reported in Mino Province (present-day Gifu Prefecture). The records of damage extend from Wakasa Bay on the Sea of Japan side to Mikawa Bay on the Pacific side. It was an earthquake that caused damage over a range unparalleled in its extent.
What is noteworthy is that this earthquake occurred at the end of Tenshō 13 (January 1586), the year after the Battle of Komaki-Nagakute in Tenshō 12 (1584), when Hideyoshi took the post of kampaku. While Hideyoshi's power was rising toward its peak, the shaking of the earth struck at the very foundations of his unification of the realm. There is a historical irony in this.
The impact of the Tenshō earthquake on Japan's sword culture can be considered both directly and indirectly.
The most important direct impact was that treasured swords and famous blades held in the castles and temples of various regions were scattered through earthquake, fire and disorder. Medieval swords were often dedicated to castle storehouses or to the treasure halls of temples and shrines, and it is thought that not a few blades were lost along with the collapse of buildings. Many of the traditional swords held by warriors of Hida and Etchū may also have been lost in the confusion after the earthquake. One of the greatest causes of breaks in the transmission of Japanese swords is dispersal caused by natural disasters, warfare and fire, and the Tenshō earthquake is considered one such example.
As an indirect impact, the large-scale damage caused by this earthquake affected the domain management and military actions of the daimyo. Daimyo who suffered damage had no choice but to prioritize the reconstruction of their domains, and their political and military trends changed.
At the time of the Tenshō earthquake, Maeda Toshiie ruled Kaga and Noto, and his son Toshinaga had also been given three districts of Etchū. They were warriors of considerable weight within the Toyotomi regime. The Maeda family traditionally placed great value on swords and was also zealous in collecting and preserving famous blades. Ōdenta Mitsuyo (National Treasure, now held by Maeda Ikutokukai) is a famous blade in the Maeda family's possession and is counted among the Five Great Swords under Heaven (Tenka Goken). It is said to have passed from the treasures of the Ashikaga shogunal family, through Ashikaga Yoshiaki, to Toyotomi Hideyoshi, and later Hideyoshi gave it to Toshiie. This tachi, said to be the work of the late Heian-period smith Miike Denta Mitsuyo, is known for its distinctive form of very wide body width and short blade length, and for its narrow straight hamon (hoso-suguha). It was transmitted as a family treasure embodying the authority of the Maeda family.
Hideyoshi also actively collected famous blades from various regions during this period. Blades offered by the imperial court and daimyo, as well as blades bestowed upon him, enriched Hideyoshi's collection. Swords were political symbols, and the gift or offering of famous blades was proof of submission.
The Tenshō earthquake was a purely natural phenomenon, but its political aftershocks cannot be ignored. Sassa Narimasa of Etchū had surrendered to Hideyoshi in the 8th month of Tenshō 13 (1585), losing most of Etchū, and in the 11th month of that year this great earthquake struck Etchū. In the same year Shikoku was also pacified, and Hideyoshi's hegemony was nearing completion.
In the history of Japanese swords, natural disasters such as earthquakes, fires and floods are among the principal causes of the dispersal of famous blades. The Tenshō earthquake was no exception, and only fragmentary records of lost famous blades and scattered swords have remained for later generations. Quietly remembered as an 'invisible rupture,' this earthquake is inscribed at the crossroads of the history of Japanese swords and Japanese history, as the fact that the ground that nurtured the Sengoku blades shook.
Etchū, which suffered heavy damage in the Tenshō earthquake, was also a region that produced master smiths in the medieval period. Etchū produced master smiths of the Sōshū tradition, represented by 'Norishige of Etchū Province.' Norishige's blades are known for a distinctive ground steel called matsukawa-hada. He is counted among the Ten Great Disciples of Masamune (Masamune Juttetsu) and is recorded in sword history as a master of the Sōshū tradition.
The Tenshō earthquake may also have directly damaged the workshops, tools and lives of smiths in the affected region. Sword-smithing is dangerous work that uses high-temperature furnaces, large anvils and heavy hammers, and if a major earthquake struck, collapse of furnaces, fires and scattering of tools would be unavoidable. The workshops of medieval smiths were centered on wooden buildings without the earthquake-resistant structures of today, and they were extremely vulnerable to strong shaking. The tools and techniques of lost smiths were not passed on to later generations, and it cannot be denied that the earthquake accelerated the 'rupture' of sword culture.
Interestingly, Toyotomi Hideyoshi was struck by another major earthquake about ten years after the Tenshō earthquake. The Keichō Fushimi earthquake of the intercalary 7th month of Bunroku 5 (1596) (estimated at around M7.5) collapsed the main tower of Fushimi Castle, which Hideyoshi had been nearing completion. It is also said that several hundred people died in the collapse of Fushimi Castle. Hideyoshi himself escaped harm but suffered a serious shock. This Fushimi earthquake occurred on the eve of the Keichō campaign (second invasion of Korea) (1597–98), and it is passed down as an event symbolizing the misfortune of Hideyoshi's later years. Over the course of Hideyoshi's life, the two great earthquakes, the Tenshō earthquake (1586) and the Fushimi earthquake (1596), shook Japanese history and left no small influence on the transmission of sword culture. The Tenshō earthquake announced the dawn of the Toyotomi regime, and the Fushimi earthquake its twilight. As tremors of the earth, they symbolize the connection between swords and earthquakes in Japanese history.
As an earthquake from before the modern era, the Tenshō earthquake holds important value as a historical source even in modern earthquake research. From the standpoint of historical seismology, it has been pointed out that this earthquake may have been one in which several active faults moved almost simultaneously, and research continues on it as an important case for deepening understanding of Japan's earthquake zones. Also from the perspective of cultural property protection, the losses that natural disasters like the Tenshō earthquake inflicted on historical cultural heritage (castles, shrines and temples, and transmitted objects) are immeasurable. The memory of this earthquake should be preserved as a historical lesson that again demonstrates the importance of disaster prevention and earthquake-resistance measures for cultural properties today. Swords are no exception. More than 430 years have passed since the Tenshō earthquake, and even now the difficulty and preciousness of protecting famous blades remain unchanged. The very history of Sengoku blades surviving to the present speaks to the significance of cultural property protection.