Sugu Site Group:
The structure of a bronze implement production center for the "country of Na," and its change over time, come to light.

Discovery of a bronze halberd mold
(Ōminami site) Recovered from the moat surrounding a settlement. The Ōminami site is a settlement from the Middle to Late Yayoi periods, located in the southern part of the Sugu site group.

Bronze halberd mold
(recovered from the Ōminami site) Late Yayoi period, second century CE. Length: 47.9 cm; width: 21.8 cm. A mold found in nearly perfect condition. The shape of a broad-bladed halberd is carved into an igneous rock called quartz-feldspar porphyry. In Kyushu of the Yayoi period, this type of stone was frequently used as raw material for molds. Its ease of working, and ability to withstand heat are thought to have made it suitable for casting.

Crucible stand
(recovered from the Sakamoto precinct, Sugu Okamoto site) Late Yayoi period, first century CE. Length: 14.6 cm; width: 13.5 cm; surviving height: 11.0 cm. Thought to have been used to support a crucible when placed in the furnace. The upper surface is seen to have a round whitish area at its center, different in color from the remainder, considered to be where the crucible leg was placed.

Bronze workshop group, Sakamoto precinct, Sugu Okamoto site Ditches surrounding an embedded pillar building are placed so they link together. Numerous artifacts related to bronze implement production, such as molds, were recovered centering on the ditches, confirming that bronze casting was conducted here. Ditches are thought to have been dug around such buildings to remove moisture from inside. Bronze workshop remains are distributed widely across the Sakamoto precinct, which is thought to have been the largest bronze workshop area in scale for the Yayoi period. A special structure encircled with a ditch has also been discovered at the Sugu Eida site, with numerous artifacts related to bronze manufacture recovered from the vicinity.

Bellows nozzle
(recovered from the Sugu Sakamoto B site) Middle to Late Yayoi, first century BCE - first century CE. Length: 14.9 cm; maximum diameter: 7.5 cm. In the casting of bronze implements, it is necessary to maintain a high temperature within the furnace; the bellows is a device for blowing air for that purpose, and the nozzle is the tip of the bellows pipe inserted into the furnace. The end is discolored to a purplish red from the heat.

Crucible
(recovered from the Sakamoto precinct, Sugu Okamoto site) Late Yayoi period, second-third centuries. A vessel placed in the furnace, for melting bronze. A spout still remains, and the reconstructed vessel had a rim diameter of about 24 cm.

Extent of the Sugu site group
In the Fukuoka plain, which is regarded as the homeland of the country of Na, there are many significant Yayoi sites. The Sugu site group is the largest aggregate of sites among these, and is thought to be the central hub of the country of Na. Settlements and cemeteries are crowded together in an area stretching about 2 km north-south by 1 km east-west. Investigation of the rice paddies has not progressed very far, but it is inferred that rice cultivation was practiced in each valley sandwiched between settlements.

Adapted from Hakkutsu sareta Nihon rettō 2010 [Excavations in the Japanese Archipelago, 2010] (Bunkachō [Agency for Cultural Affairs], ed., Asahi Shimbun Publications, 2010).

Sugu Site Group, Kasuga City, Fukuoka Prefecture

The royal center of Na

Sugu is a large-scale group of sites from the Middle to Late Yayoi periods (second century BCE - third century CE), located in and around the Kasuga hills of the southern Fukuoka plain. Settlements, cemeteries, rice paddies etc. are crowded together in an area stretching about 2 km north-south by 1 km east-west.

The Fukuoka plain is regarded as the former location of the gcountry of Nah noted in the Chinese chronicles, History of the Later Han and History of the Kingdom of Wei, and while it is dotted with Yayoi sites such as Itazuke which are famous nationwide, the Sugu group is the largest among these.

While thus noteworthy in scale, the region has also become noted for its concentrated finds of bronze implements of all types and the molds used in their manufacture, priceless artifacts showing cultural advancement. At the Sugu Okamoto site comprising the group's core, a jar burial with numerous grave goods, regarded as a royal grave of the country of Na, was discovered in 1899, and the area is accordingly regarded as the hub of Na.

Production and distribution of varieties of bronze implements

The number of molds for bronze implements discovered so far for the Sugu group and the Goryō site located to its northwest exceeds 150 items. This accounts for nearly half of the total found for Kyushu, and is a prominent proportion of the discoveries even when viewed nationwide. Bronze implements produced at this locale include many varieties, such as socketed spearheads, halberds, swords, small mirrors, and small bells, with the socketed spearheads in particular being manufactured in large amounts, and thought to have been distributed not only across the breadth of northern Kyushu, but also to Shikoku and the Chūgoku region, and the southern part of the Korean peninsula as well.

Workshops become concentrated

Bronze manufacturing is known to have begun in the first half of the Middle Yayoi period (second century BCE), and appears to have been conducted continually until the end of the Yayoi. From discoveries of molds it is inferred that in the Middle Yayoi bronze production was carried out in dispersed fashion in each village, but a trend for concentration in the vicinity of the Sugu Okamoto site can be seen in the Late Yayoi period.

At the Sugu Okamoto site's Sakamoto precinct, and at the Sugu Eida site, along with molds and many other artifacts related to bronze manufacture, features seen as those of a workshop where bronze casting was conducted have been found. Both instances consist of embedded-pillar buildings surrounded by ditches, with the latter inferred to be facilities for removing moisture from inside the workshop. (Hirata Sadayuki, Inoue Yoshinari)

Principal artifacts

Bronze sword mold
(recovered from the Goryō site) and a bronze sword (from the Tateishi site) Late Yayoi period, first century CE. Mold length: 31.4 cm; width: 10.2 cm. Sword length (base fragment): 13.3 cm; width: 5.6 cm. This type of bronze sword is called by various names such as the Warring States style sword, and as its locus of production was unclear it was held by some to come from the Chinese mainland. But in an investigation of the Goryō site in the 2008 Fiscal Year a mold of this same type was discovered, and it is understood to have been made within the archipelago as well. The sword find is from the Tateishi site in the southeastern part of the Sugu site group.

(Item at left)
Bronze socketed spearhead mold
(Ōtani site) Middle Yayoi period, first century BCE. Length: 15.9 cm. Made with a material resembling the gsoapstoneh schist molds recovered from the Korean peninsula, this is an early example of a mold.

(Item at right)
Bronze socketed spearhead core
(Sugu Sakamoto B site) Late Yayoi period, first century CE. Length (fourth item from bottom): 3.9 cm. Used to make the socket for the spear shaft. All parts are represented, from the pouring gate to the area near the tip.

Comma-shaped glass bead mold
(Akaide site) Middle to Late Yayoi period, first century BCE - first century CE. Length: 6.3 cm. Molds for comma-shaped beads are carved in the center and at the left edge. The mold at center retains nearly its complete shape, and it is seen that large glass comma-shaped beads of 4 cm length were made with this mold.

Diagram of mold for casting bronze socketed spearhead

Adapted from Hakkutsu sareta Nihon rettō 2010 [Excavations in the Japanese Archipelago, 2010] (Bunkachō [Agency for Cultural Affairs], ed., Asahi Shimbun Publications, 2010).