Hikawa Bronze Swords Day

What Is Hikawa Bronze Swords Day?

Every July 12th is "Hikawa Bronze Swords Day" (ひかわ銅剣の日, Hikawa Dōken no Hi), established by the town of Hikawa (now part of Izumo City) in Shimane Prefecture. On July 12, 1984, an extraordinary archaeological discovery was made at the Kojindani site (荒神谷遺跡) in what was then the town of Hikawa (now Izumo City), Shimane Prefecture: 358 bronze swords were unearthed from a single site — the largest collection of bronze swords ever discovered in one location in Japan. The find transformed scholarly understanding of the Yayoi period (300 BCE – 300 CE) and the ancient culture of the Izumo region.

The Discovery at Kojindani

In 1983, a survey ahead of the construction of a regional farm road turned up fragments of Kofun-period Sue ware pottery, which led to an excavation. Swords appeared in the very first trench; at first the team expected perhaps a hundred, but more and more emerged until the count reached 358. The swords were all of the same type ("medium-slender type c"), about 50 cm long and weighing a little over 500 g, and had been deliberately set on edge in four neat rows on a hillside terrace — not randomly discarded, but intentionally buried. The scale of the find was unprecedented: it exceeded the total number of bronze swords (about 300) that had been excavated in all of Japan until then.

More Discoveries at Kojindani

The initial 358-sword discovery was followed the next year (1985) by additional remarkable finds at the same site: 6 bronze bells (銅鐸, dōtaku) and 16 bronze spear tips (銅矛, dōboko) were discovered nearby. Together, these artifacts represented a ritual deposit of extraordinary magnitude. In 1996, the nearby Kamo-Iwakura site (加茂岩倉遺跡), about 3 km away, yielded 39 dōtaku — the largest single cache of bronze bells ever found in Japan. The concentration of such spectacular finds in the Izumo region has fundamentally reshaped understanding of Yayoi-period ritual and political organization.

What the Swords Tell Us

Bronze swords of this era are thought to have been used more as ritual objects than as weapons for actual combat. Their careful deposition suggests a large-scale ritual event — possibly a ceremony conducted by or for a powerful chieftain or religious leader in the Izumo region. Izumo is already significant in Japanese mythology as the home of Ōkuninushi no Mikoto, the deity associated with the Izumo Grand Shrine (出雲大社). The archaeological discoveries at Kojindani suggest that Izumo was indeed a major center of power in the Yayoi period. Of the 358 swords, 344 bear an "×" mark carved after casting on the tang; similar marks have been found only on the dōtaku from Kamo-Iwakura, hinting at a link between the two sites. The meaning of the mark is still unknown.

Fun Facts

• National Treasure: The Kojindani bronze swords were designated an Important Cultural Property in 1985 and, together with the bells and spearheads, a National Treasure in 1998. They are housed at the Shimane Museum of Ancient Izumo (島根県立古代出雲歴史博物館) in Izumo City.
• Kojindani Archaeological Site: The site itself was designated a National Historic Site in 1987 and is preserved as Kojindani Historic Park, with the Kojindani Museum explaining the excavation.